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Methylammonium chloride (MACl) additive is almost irreplaceable in high‐performance formamidine perovskite photovoltaics. Nevertheless, Some of the problems that can arise from adding MACl are rarely mentioned. Herein, it is proposed for the first time that the addition of MACl would cause the non‐stoichiometric ratio in the perovskite film, resulting in the halogen vacancy. It is demonstrated that the non‐synchronous volatilization of methylamine cations and chloride ions leads to the formation of halogen vacancy defects. To solve this problem, the NH4HCOO is introduced into the perovskite precursor solution to passivate the halogen vacancy. The HCOO− ions have a strong force with lead ions and can fill the halogen vacancy defects. Consequently, the champion devices' power conversion efficiency (PCE) can be improved from 21.23% to 23.72% with negligible hysteresis. And the unencapsulated device can still retain >90% of the initial PCE even operating in N2 atmosphere for over 1200 h. This work illustrates another halogen defect source in the MACl‐assisted formamidine perovskite photovoltaics and provides a new route to obtain high‐performance perovskite solar cells. [ABSTRACT FROM AUTHOR]

The perovskite photovoltaic field has developed rapidly within a decade. In particular, formamidinium (FA)‐rich perovskite allows a broad absorption spectrum, and is considered to be one of the most promising perovskite materials. Great progress has been achieved, and most recorded high‐efficient perovskite solar cells (PSCs) used the FA‐rich perovskite light absorption layer. However, the black α‐phase formamidinium lead iodide (FAPbI3) perovskite easily transforms into an undesirable δ‐phase at a low temperature. Thus, researchers have put a lot of effort into deeply understanding the phase transformation and stabilization mechanism of FA‐rich perovskite. Herein, the fundamental physical properties of FAPbI3 materials, including crystal structure, phase‐transition temperature, charge‐carrier dynamics, etc. are summarized, and establish a complete phase evolution with temperature by reviewing previous reports. The intrinsic and external factors are subsequently discussed for influencing the stability of FAPbI3 perovskite and the remarkable breakthroughs of FA‐rich PSCs in recent years are reviewed. Moreover, a series of strategies to stabilize FA‐rich perovskite is summarized, including but not limited to compositional engineering, passivating engineering, processing engineering, and strain engineering. Finally, several new viewpoints are provided for improving the efficiency and stability of PSCs. This review may be regarded as a reference project for preparing high‐efficient and stable perovskite photovoltaic devices. [ABSTRACT FROM AUTHOR]

• NC 70 BA plays a dominant role in the photocurrent generating and charge transport. • The separation of exciton of NCBDT-4Cl mainly occurs on the NCBDT-4Cl/NC 70 BA interface. • The OSCs based on NC 70 BA exhibit a significant increase of 10% in PCE. • The shallower energy levels and better compatibility for double side chain fullerene derivative NC 70 BA than single side chain fullerene PC 71 BM. In this study, ternary organic solar cells (OSCs) are fabricated with the PBDB-T-2F as a polymer donor and NCBDT-4Cl as a fullerene-free acceptor, double side chain fullerene derivative NC 70 BA as a third component material and single side chain fullerene PC 71 BM as reference third component materials. The NC 70 BA-based ternary OSCs exhibit the highest PCE of 13.82%, which is 10% higher than that of PBDB-T-2F:NCBDT-4Cl binary OSCs and slightly higher than PC 71 BM-based ternary OSCs (13.24%). Detailed studies suggest that the shallow LUMO levels and double side chain for NC 70 BA is beneficial to broaden energy bandgap and improve compatibility, which is enhancing J SC and FF value. This work suggests that double side chain fullerene derivative NC 70 BA as third component materials is a promising way to finely tune the detailed photovoltaic parameters and further improve the photovoltaic performance of OSCs. [ABSTRACT FROM AUTHOR]

• Double modification – simultaneously using MoS 2 as buffer layer and additives. • MoS 2 film acts as a protective and ideal electron blocking candidate. • MoS 2 doped CH 3 NH 3 PbI 3 , enhance the quality of the perovskite film. • CH 3 NH 3 PbI 3 : MoS 2 heterojunction promote charge transfer. Organic-inorganic perovskite solar cells emerge as one of the most promising photovoltaic technology due to its high performances. Particularly, inverted perovskite device architecture, due to low temperature processing, have a great potential in commercialization. High-crystalline quality perovskite film and interfacial passivation are essential to yield high performance devices. In this work, we employ a simple strategy of using molybdenum disulfide (MoS 2) as both the interfacial layer and the additive to prepare efficient PSCs. MoS 2 as an additive in perovskite can form the CH 3 NH 3 PbI 3 :MoS 2 heterostructure, resulting in the homogeneous perovskite film with larger crystal grains. In addition, MoS 2 as the buffer layer (BL) between poly (3,4-ethylene dioxythiophene)-poly (styrene sulfonate) (PEDOT:PSS) and perovskite can prevent the decomposition of perovskite film by avoiding the direct contact with the hydrophilic PEDOT:PSS films. On tedious optimization, the champion device based on active layer of CH 3 NH 3 PbI 3 :MoS 2 (10 v%) as well as employing MoS 2 buffer layer shows a remarkable improvement in the power conversion efficiency (PCE) (from 15.29% to 18.31%) and a better stability, with 87% of the initial efficiency sustained after 20 days. Our finding herein provides a promising way to fabricate high efficiency and stable photovoltaic devices. [ABSTRACT FROM AUTHOR]

Carbon-based perovskite solar cells aroused huge attention for their simple, low-cost device fabrication processing and excellent stability. However, the fully low-temperature preparation and flexibility of carbon-based perovskite solar cells remain huge challenges. Here we demonstrate the fabrication of carbon-based perovskite solar cells processed at fully low-temperature, which take thermally evaporated cadmium sulfide as efficient electron transport layer, and obtain an optimal power conversion efficiency of 13.22%. With the decoration of PCBM, the separation of charges at the interface is facilitated and the recombination is hindered, so a higher fill factor is obtained and the efficiency is further improved to 14.28%. Our devices also exhibit good long-term durability and excellent ultraviolet stability. Based on the fully low-temperature preparation process, carbon-based flexible devices are further developed with an optimal efficiency over 9% and considerable mechanical stability, which can serve as the roof-top photovoltaics and power sources for wearable devices. Image 1 • Fully low-temperature processed and flexible carbon-based PSCs with excellent efficiency and stability are demonstrated. • First use of CdS as electron transport layer for carbon-based PSCs. • With the decoration of PCBM, efficiency of the best-performing device is greatly enhanced. [ABSTRACT FROM AUTHOR]

• PEIE/TiO X bilayer films were produced by spin-coating the blend solution of PEIE and TiO X. • PEIE/TiO X showed better chemical stability and charge carrier transport ability. • PEIE/TiO X could replace Ca or TiO X as the EEL in PSCs devices. One of the challenges facing the fabrication of high-performance conventional structure polymer solar cells (PSCs) is the development of new interface materials that have better air stability and charge carrier collection and transport ability. In this study, the mixture thin films of polyethylenimine ethoxylated (PEIE) and TiO X are developed as the electron extraction layer (EEL) and Ag as the cathode for the application in PSCs, replacing the Ca/Al composite cathode. Ultraviolet photoelectron spectroscopy (UPS) and space-charge-limited current (SCLC) measurements demonstrate that PEIE:TiO X /Ag shows appropriate energy levels, substantially reduced barrier potential, weakened charge carrier recombination and enhanced electron mobility. As a result, the PEIE:TiO X -based PSCs demonstrate not only an enhanced power conversion efficiency (PCE) of 10.94% but also the photovoltaic performance insensitive to the storage time, yielding an aged PCE that is 92% of the fresh PCE. This result can be further explained by the dependence of the charge carrier mobility on storage time. Our work suggests exploiting the PEIE:TiO X /Ag composite thin films as the composite cathode replacing Ca/Al thin films for successfully enhancing the photovoltaic performance and improving the stability of PSCs. [ABSTRACT FROM AUTHOR]

Abstract Organic-inorganic lead halide perovskite solar cells have garnered enormous interest in scientific communities due to comparable power conversion efficiencies and solution-processed fabrication techniques. Among them, carbon-based perovskite solar cells seem to be one of the most promising candidates for addressing the stability issue while suffering from inferior efficiency or high processing temperature. Herein, we introduce low-temperature processed Zn-doped SnO 2 (below 200 °C) as an effective electron transport layer in perovskite solar cells for the first time, and demonstrate a low-temperature carbon-based device with Cu-phthalocyanine as hole transport layer. We find that Zn doping contributes to a more suitable energy level alignment and an improved conductivity for SnO 2 films. As a result, the electron transfer and extraction are enhanced and the charge recombination is suppressed. In addition, devices with Zn-doped SnO 2 have a wider depletion region, leading to an enhanced photovoltaic performance. An optimal efficiency of 17.78% can be obtained after 2 mM Zn doping. Furthermore, these devices, introducing highly stable and hydrophobic Cu-phthalocyanine and carbon, maintain almost 100% of their initial efficiencies over 1200 h in ambient air. Our study paves the way for developing highly efficient and flexible carbon-based perovskite solar cells. Graphical abstract 17.78% efficient low-temperature carbon-based planar perovskite solar cell using Zn-doped SnO 2 electron transport layer is demonstrated. Zn doping contributes to a more favorable energy level alignment, an improved conductivity and a wider depletion region, resulting in an enhanced performance. The low-temperature and solution process realize flexible perovskite solar cells. Unlabelled Image Highlights • A high efficiency of 17.78% is achieved among carbon-based perovskite solar cells. • The whole process is conducted at low temperature (below 200 °C), enabling the fabrication of flexible devices. • The low-temperature processed Zn doped SnO 2 is introduced as an electron transporting layer in perovskite solar cells. • Excellent stability is obtained by utilizing CuPc and Carbon as hole transporting layer and electrode. [ABSTRACT FROM AUTHOR]

Abstract Ternary organic solar cells (OSCs) are fabricate using a single wide-bandgap poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b0]dithiophene))-alt-(5,5-(10,30-di-2-thienyl-50,70-bis(2-ethylhexyl)benzo[10,20-c:40,50-c0]dithiophene-4,8-dione))] (PBDB-T) as the donor material and 3,9-bis (2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis (4-hexylphenyl)-dithieno[2,3-d:2′, 3′-d′]-s-indaceno[1,2-b:5,6-b']dithiophene) (ITIC) as the acceptor and poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-(3,3′-difluoro-2,2′-bithiophene)-5,5′-diyl] (F N2200) as third component materials. Due to the strong absorption ability at the short-wavelength region. The best power conversion efficiency (PCE) of 10.9% is achieve for the OSCs via incorporating 10 wt% F N2200 in blend-acceptor materials, with an enhance the short-circuit current (J SC) of 17.6 mA cm−2, fill factor (FF) of 68.0% and stable open-circuit voltage (V OC) of 0.91 V relative to binary OSCs. The short-wavelength absorption windows of F N2200 is favourable the harvesting of as many as possible photons and the enhance exciton dissociation ratio at the ITIC/F N2200 interface due to the deeper LUMO energy level of F N2200 relative to ITIC molecule. Meanwhile, the incorporation small amount of F N2200 is weaken monomolecular recombination and bimolecular recombination under open-circuit and short-circuit conditions respectively and enhance the charge carrier mobility. The use of PBDB-T as donor and the blend of ITIC and F N2200 as an electron acceptor provides a useful strategy for exploring high-performance ternary OSCs. Highlights • Ternary OSCs were fabricated with F N2200 as third component materials. • The ternary photoactive layer is weaken charge carrier recombination. • The improvement of exciton-dissociation at the PBDB-T/acceptor interface. • The enhanced photovoltaic performance, especially under weak light intensity. [ABSTRACT FROM AUTHOR]

Highlights • PbS thin films were prepared through a facile MACBD method. • The resultant PbS CEs exhibit higher catalytic activity than the PbS-CBD CEs. • A maximum efficiency of 4.85% was achieved with PbS-1 CE. • The MACBD method has great potential in fabricating photo-electrochemical devices. Abstract In this study, PbS thin films are deposited on FTO substrate via a rapid and facile microwave-assisted chemical bath deposition (MACBD) and then used directly as the counter electrodes (CEs) for CdS/CdSe quantum dots co-sensitized ZnO nanorods array solar cells (QDSSC). The resultant PbS CEs show good uniformity, strong adhesion to the FTO and superior electrocatalytic activity for the reduction of polysulfide electrolyte compared to the PbS CEs prepared with conventional CBD method. The combination of ZnO/CdS/CdSe photoanode with the optimum PbS CE shows appreciated power conversion efficiency (PCE) of 4.85%. The augmented photovoltaic performance can be attributed to its high electrocatalytic activity for polysulfide reduction in QDSSC, which results in a low charge transfer resistance at the interface of CE/electrolyte. The results demonstrate the potential application of this MACBD method in fabricating efficient metal sulfide counter electrode for QDSSC. [ABSTRACT FROM AUTHOR]

Abstract We describe a ternary photoactive layer based on PffBT4T-2OD as a donor with a blend of dihydronaphthyl-based C60 bisadduct (NCBA) and PC 71 BM as the acceptor. It offers ideal exciton dissociation, an ideal charge-carrier recombination and photovoltaic performance relationship, and improves the power-conversion efficiency (PCE) and stability of polymer solar cells (PSCs). NCBA has a broad visible-light absorption spectrum and shallower lowest unoccupied molecular orbital (LUMO) energy levels, which enhance exciton dissociation and charge-carrier transport and suppress charge-carrier recombination. This remarkably increases the photocurrent density and fill factor. An optimized PCE of 9.79% was achieved for the ternary PffBT4T-2OD:NCBA:PC 71 BM(1:0.24:0.96)-based PSCs. The mechanism was exciton dissociation at the PffBT4T-2OD/NCBA, PffBT4T-2OD:PC 71 BM, and NCBA/PC 71 BM interfaces. This simultaneously enhances the exciton-dissociation ratio and charge-carrier transport. Meanwhile, PSCs with 20% NCBA as third-component materials exhibit improved thermal stability and photo-stability leading to a lower ratio of PCE under long-time thermal-annealing and visible-light-illuminated treatment. This work indicates that NCBAs are third-component materials that significantly improve PSC performance. Highlights • Ternary PSCs were fabricated with NCBA as third component materials. • The ternary photoactive layer is weaken charge carrier recombination. • The improved exciton-dissociation at the donor–blend acceptor interface. • The enhanced photovoltaic performance, thermal stability and photo stability. [ABSTRACT FROM AUTHOR]

Abstract Fullerenes have been widely used as the electron transport layers (ETL) for planar-heterojunction perovskite solar cells (PSCs), due to their superior abilities in electron transporting, hysteresis suppression and low-temperature processing. Here, we demonstrate a novel inverted PSC with evaporated C 60 as ETL and dopant-free copper phthalocyanine (CuPc) as hole transport layer (HTL). The C 60 ETL can not only transport photogenerated electrons, but also passivate grain boundaries and surfaces of perovskite films effectively. By optimizing the thickness of the C 60 ETL, a champion power conversion efficiency (PCE) of 16.72% is obtained with almost no hysteresis and less than 10% decay in efficiency is observed during a two-week stability test. To the best of our knowledge, this is the highest efficiency of the inverted PSCs employing CuPc as HTL. For comparison, the devices using PCBM as ETL are also prepared and only achieve a highest efficiency of 15.74%. Various characterizations and analyses attest the enhanced charge transport and extraction as well as suppressed charge recombination and hysteresis for the C 60 -based devices. Since all the processes are accomplished under a low temperature, this enable us to fabricate flexible PSCs on polyethylene terephthalate (PET) substrates with a highest PCE of 12.96%. Our work provides a new strategy for fabricating cost-effective, highly efficient and hysteresis-free flexible PSCs in mass production. Graphical abstract Novel efficient C 60 -based inverted perovskite solar cells with negligible hysteresis are demonstrated. A champion power conversion efficiency (PCE) of 16.72% and 12.96% is obtained for the devices prepared on rigid and flexible substrates, respectively. Image 1 Highlights • Novel inverted perovskite solar cells (PSCs) with Cu-phthalocyanine and C 60 as HTL and ETL, respectively. • 16.72% efficiency is obtained, which is the highest efficiency of the inverted PSCs employing CuPc as HTL. • 12.96% efficiency is obtained for the flexible device. • Almost no hysteresis is observed. • Cost-effective, easy to prepare and highly stable. [ABSTRACT FROM AUTHOR]

Abstract Zinc oxide (ZnO) as an electron transport material has been used in regular planar perovskite solar cells (PSCs). Herein, ZnO nanoparticles serve as an additive directly in perovskite active layer in order to fabricate a bulk-heterojunction inverted planar PSC. The CH 3 NH 3 PbI 3-x Cl x :ZnO bulk heterojunction is prepared by mixing ZnO nanoparticles into CH 3 NH 3 PbI 3-x Cl x precursor solution. ZnO nanoparticles act as catalytic centers and induce the growth of perovskite grains leading to the formation of large-size perovskite crystals. Remarkably, hysterysis-free power conversion efficiency of 17.26% is achieved when precisely control the concentration of ZnO nanoparticles in CH 3 NH 3 PbI x Cl 3-x :ZnO bulk heterojunction active layer. The presence of ZnO nanoparticles in the perovskite films enhances the conductivity and electron mobility. Efficient charge injection of CH 3 NH 3 PbI x Cl 3-x :ZnO film can improve charge extraction in the PSCs. Moreover, the PSCs with CH 3 NH 3 PbI x Cl 3-x :ZnO bulk heterojunction exhibit high fill factor of 77.3% and short current density of 22.71 mA cm−2, which is attributed to improved perovskite quality. The bulk heterojunction structure is fabricated by combining perovskite and metal oxides, which is of great importance to the development and commercialization of PSCs in the future. Graphical abstract Image 1 Highlights • A CH 3 NH 3 PbI 3-x Cl x :ZnO bulk heterojunction exits in the perovskite solar cell. • ZnO nanoparticles improve light harvesting efficiency of perovskite solar cell. • ZnO nanoparticles lead to the formation of large-size perovskite crystals. • ZnO nanoparticles improve conductivity and electron mobility of perovskite film. [ABSTRACT FROM AUTHOR]

Electron transport layer (ETL), functioning as the electron transportation and extraction layer as well as hole-blocking layer, plays an important role in planar perovskite solar cells (PSCs). Majority of the state-of-the-art PSCs contain a TiO 2 ETL always requiring a high temperature (500 °C) treatment, which is both energy-consuming and incompatible with flexible substrates, thus hindering large-scale application in flexible devices. Here, we demonstrated a low-temperature (70 °C) solution-processed Mg-doped rutile TiO 2 as ETL in planar PSCs, while the thermal-evaporated copper phthalocyanine (CuPc) and doctor-bladed carbon were introduced as the hole transport layer (HTL) and counter electrode, respectively. The as-prepared PSC obtains a 15.73% power conversion efficiency (PCE), which is quite an excellent efficiency among carbon-based planar PSCs, getting an increase by 16% compared to the 13.56% PCE of the pristine TiO 2 -based device. The prominent increment is mainly attributed to the faster charge extraction, better electrical conductivity and suppressed charge recombination of Mg-doped TiO 2 . Besides, using highly stable CuPc and commercial carbon makes the as-prepared PSCs highly durable over 30 days when exposed to the ambient air with a relative humidity of 50%. Since all the processes are conducted under 100 °C, our work paves a way for developing cost-effective and highly stable PSCs compatible with flexible substrates. [ABSTRACT FROM AUTHOR]

A dihydronaphthyl-based C60 bisadduct (NCBA) acceptor is introduce as a third component to typical PTB7: PC 71 BM binary polymer solar cells (PSCs). NCBA play bridging role between the lowest unoccupied molecular orbital (LUMO) of PTB7 and PC 71 BM and provides more routes for charge carrier transfer at the interface between PTB7 and PC 71 BM, a higher open-circuit voltage ( V OC ) realize upon addition of NCBA can be achieve relative to the neat PC 71 BM as an electron acceptor. The strong visible light absorption in the range from 350 to 700 nm of NCBA molecule compared with PC 71 BM molecule, it has the effect of apparently complementary visible light absorption compare with the binary PTB7:PC 71 BM thin films. The current density–voltage ( J - V ) characteristics dependent on incident light intensity were employed and to analyze the effect of NCBA concentration on the charge carrier recombination process of ternary PSCs. The crystallinity and surface morphology of the ternary PTB7:NCBA:PC 71 BM thin films with NCBA concentration is 15% of blend acceptor is similar to that of the binary PTB7:PC 71 BM thin films, which guarantees suitable efficient exciton dissociation and charge carrier transport. The transient photovoltage (TPV) and transient photocurrent (TPC) were measured, and the results illustrate the effect of NCBA as the third component materials in terms of higher charge carrier density and long charge carrier lifetime and weaken charge carrier recombination. [ABSTRACT FROM AUTHOR]

In this work, an efficient and stable inverted planar perovskite solar cell (PSC) with water additive has been prepared in ambient air. Adding moderate water additive to CH 3 NH 3 PbI 3−x Cl x precursor solution leads to growth in quality of CH 3 NH 3 PbI 3−x Cl x film, because the boiling point of water is lower than that of N, N-dimethylformamide. The annealing temperature of the CH 3 NH 3 PbI 3−x Cl x film is controlled to 105 °C (slightly higher than the boiling point of water) to obtain the dense perovskite film rapidly in ambient environment with ~ 40% relative humidity. The highest power conversion efficiency (PCE) of PSC with water additive is 14.02%, higher than that (11.17%) of the reference device without water additive. In addition, the aqueous CH 3 NH 3 PbI 3−x Cl x solution is transformed into the stable perovskite film through the method of rapid annealing. The stable CH 3 NH 3 PbI 3−x Cl x ·nH 2 O system can resist the decomposition of perovskite film and weaken iodide ion migration in PSCs, which enhance stability of the device under the atmospheric environment. After being stored in the air for 120 h, the PSC device with water additive still has an PCE of 12.01%, higher than that (1.64%) of the reference device. [ABSTRACT FROM AUTHOR]

A low-temperature, solution-processed molybdenum oxide (MoO X ) layer and a facile method for polymer solar cells (PSCs) is developed. The PSCs based on a MoO X layer as the hole extraction layer (HEL) is a significant advance for achieving higher photovoltaic performance, especially under weaker light illumination intensity. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements show that the (NH 4 ) 6 Mo 7 O 24 molecule decomposes and forms the molybdenum oxide (MoO X ) molecule when undergoing thermal annealing treatment. In this study, PSCs with the MoO X layer as the HEL exhibited better photovoltaic performance, especially under weak light illumination intensity (from 100 to 10 mW cm −2 ) compared to poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)-based PSCs. Analysis of the current density-voltage ( J - V ) characteristics at various light intensities provides information on the different recombination mechanisms in the PSCs with a MoO X and PEDOT:PSS layer as the HEL. That the slopes of the open-circuit voltage ( V OC ) versus light illumination intensity plots are close to 1 unity ( kT/q ) reveals that bimolecular recombination is the dominant and weaker monomolecular recombination mechanism in open-circuit conditions. That the slopes of the short-circuit current density ( J SC ) versus light illumination intensity plots are close to 1 reveals that the effective charge carrier transport and collection mechanism of the MoO X /indium tin oxide (ITO) anode is the weaker bimolecular recombination in short-circuit conditions. Our results indicate that MoO X is an alternative candidate for high-performance PSCs, especially under weak light illumination intensity. [ABSTRACT FROM AUTHOR]

We demonstrate the application of low-temperature carbon counter electrode in fabricating large-area hole-conductor-free perovskite solar cell. A mesoscopic TiO 2 film was deposited on a transparent conductive fluorine-doped tin oxide substrate by screen printing method. Then commercial conductive carbon slurry was printed to prepare the counter electrode at a temperature of 130 °C. The light absorber, CH 3 NH 3 PbI 3 , was formed instantly inside the pores of the entire TiO 2 /carbon layer upon single-step deposition of CH 3 NH 3 PbI 3 precursor. The devices were characterized with XRD, SEM, and UV–vis absorption spectroscopy. As a result, an energy conversion efficiency of 3.3% with an active area of 2.25 cm 2 was got under AM1.5G condition and there was no obvious decay during a testing period of 624 h. The carbon counter electrode has the features of low-cost and low-temperature preparation, giving it potential for application in the large-scale flexible fabrication of perovskite solar cells in the future [ABSTRACT FROM AUTHOR]

Solution-processed titanium (IV) oxide bis(2,4-pentanedionate) (TOPD) as an electron extraction layer (EEL) and the blend of thieno[3,4-b]thiophene/benzodithiophene (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC 71 BM) as a photoactive layer with a power conversion efficiency ( PCE ) of 9.15% are demonstrated. Analysis of the current-voltage ( J-V ) characteristics under dark conditions provides information on the weaker leakage current of TOPD-based polymer solar cells (PSCs) compared to ZnO-based PSCs. By investigating the photovoltaic performance under different light illumination intensities, we achieved an improvement of photovoltaic performance under weak light illumination intensity for TOPD-based PSCs. The enhanced photovoltaic performance under weak light illumination intensity for TOPD-based PSCs can be experimentally explained by the higher open-circuit voltage ( V OC ) value under lower light illumination intensity compared to ZnO-based PSCs. This indicates that the TOPD layer in the PSCs reduced the probability of charge carrier recombination at trap sites and improved the charge carrier collection and transport efficiency under weaker light illumination intensity. Simultaneously, the similar fill factor and short circuit current density of two PSCs can be experimentally explained by the weak bimolecular recombination between the photoactive layer and indium-tin-oxide electrode with the different EEL materials under different light illumination intensity. [ABSTRACT FROM AUTHOR]

We prepared ternary organic solar cells (OSCs) by incorporating the medium wavelength absorption polymer PSEHTT into the PM6:L8-BO binary system. The power conversion efficiency (PCE) is improved from 15.83% to 16.66%. Although the fill factor (FF) is slightly reduced, the short-circuit current density (JSC) and open-circuit voltage (VOC) are significantly increased at the same time. A small amount of PSEHTT has a broad absorption spectrum in the short wavelength region and has good compatibility with PM6, which is conducive to fine-tuning the photon collection and improving the JSC. In addition, the highest occupied molecular orbital (HOMO) energy level of PSEHTT is deeper than that of PM6, which broadens the optical bandgap. This study provides an effective method to fabricate high-performance ternary OSCs by using a lower concentration of PSEHTT with PM6 as a hybrid donor material, which ensures a better surface and bulk morphology, improves photon collection, and broadens the optical bandgap. [ABSTRACT FROM AUTHOR]

High-performance Inverted polymer solar cells (PSC) were fabricated with ammonium heptamolybdate (NH 4 ) 6 Mo 7 O 24 −4H 2 O as hole extraction layer (HEL), and the blend of the poly(3-hexylthiophene) (P3HT):indene-C60 bisadduct (ICBA) as photoactive layer, using the structure of ITO/ZnO/P3HT:ICBA/(NH 4 ) 6 Mo 7 O 24 /Ag. Correspondingly, the influence of different annealing time of ammonium heptamolybdate on carrier mobility and thus device performance were investigated. The power conversion efficiency ( PCE ) has been optimized from 4.12% to 6.24% after thermal annealing treatment of (NH 4 ) 6 Mo 7 O 24 layer at 130 °C for 15 min. The results of ultraviolet photoelectron spectroscopy (UPS) curve clearly proven the increase of conduction-band minimum (CBM) and valence-band maximum (VBM) energy level of (NH 4 ) 6 Mo 7 O 24 layer upon thermal annealing, which is caused by the decrease of barrier potential between HOMO of P3HT and HEL. This obviously facilitate hole transport hole transport between HOMO levels of P3HT and HEL block electron transfer between LUMO levels of P3HT and Ag electrode. The space charge-limited current (SCLC) test has further confirmed the enhanced hole collection and transport capability of (NH 4 ) 6 Mo 7 O 24 after thermal annealing treatment. [ABSTRACT FROM AUTHOR]

The solution processable electron extraction layer (EEL) is crucial for polymer solar cells (PSCs). Here, we investigated titanium (diisopropoxide) bis(2,4-pentanedionate) (TIPD) as an EEL and fabricated inverted PSCs with a blend of poly(3-hexylthiophene) (P3HT) and indene-C60 bisadduct (ICBA) acting as the photoactive layer, with a structure of ITO/TIPD/P3HT:ICBA/MoO 3 /Ag. After thermal annealing treatment at 150 °C for 15 min, the PSC performances increased from 3.85% to 6.84% and they achieve stable power conversion efficiency ( PCE ), with a similar PCE compared with TiO 2 as an EEL by the vacuum evaporated method. Fourier transform infrared spectroscopy (FTIR) and ultraviolet photoelectron spectroscopy (UPS) confirmed that the TIPD decomposed and formed the Ti O bond, and the energy level of the lowest unoccupied molecular orbital and the highest occupied molecular orbital increased. The space charge limited current (SCLC) measurements further confirmed the improvement in electron collection and the transport ability using TIPD as the EEL and thermal annealing. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ternary PSCs were fabricated with PBDB-TF as third component materials. • The improvement of charge dynamics process of ternary photoactive layer by ternary strategy. • The improved exciton-dissociation at the donor–blend acceptor interface. In this manuscripts, a ternary polymer solar cells (PSCs) are fabricate with two "D18-series" donor (D18-Cl and D18) as blend donor and T6 as acceptor. The effects of D18-Cl and D18 in ternary PSC on the film morphology, photoelectronic properties and charge carrier dynamics were systematically investigated. By finely adjusting the D18 content, a power conversion efficiency (PCE) of 16.66 % is achieved in the optimized ternary PSCs with 35 wt% D18 in donor, resulting from significantly improved short-circuit-current density (J SC) of 26.80 mA cm−2 in comparison with those of D18-Cl:Y6 binary PSCs. The J SC of ternary PSCs monotonously increase along with the incorporation of D18, indicating that D18 is comprehensively optimal short wavelength photon harvesting compared with D18-Cl. Both D18-Cl and D18 are shown similar highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels, which is beneficial to efficient charge transport at the blend donor domain. Our work indicates that the blend of D18-Cl and D18 as blend donor and Y6 as electron acceptor to boost photovoltaic performance in the ternary PSCs. [ABSTRACT FROM AUTHOR]

In this paper, ternary polymer solar cells (PSCs) consisting of two blend donors (FTAZ and PTB7-Th) and one acceptor (N3) with similar highest occupied molecular orbital (HOMO) energy levels, different absorption peaks and cascading lowest unoccupied molecular orbital (LUMO) energy levels are built. The ternary PSCs achieve higher photovoltaic performance and better thermal stability compared to the FTAZ:N3 binary PSCs. The A medium wavelength absorption FTAZ polymers and long wavelength absorption PTB7-Th polymers as the blend donor, and near-infrared wavelength absorption N3 as the acceptor. The optimize ternary PSCs exhibit a maximum power conversion efficiency of 15.65%, with an open-circuit voltage of 0.852 V, a short-circuit current of 25.25 mA cm − 2, and an FF of 72.5%. This performance of device is attributed to more efficient exciton dissociation and suppression of charge recombination within ternary films. The ternary PSCs also show good crystallinity and surface morphology at room temperature and after thermal annealing for 20 h at 70 °C, which is attribute to the better thermal stability of the ternary PSCs. • Ternary PSCs were fabricated with PTB7-Th as third component materials. • The improvement of charge dynamics process of ternary photoactive layer by ternary strategy. • The improved exciton-dissociation at the donor–blend acceptor interface. [ABSTRACT FROM AUTHOR]

Photo-annealing treatment has successfully been demonstrated in organic solar cells (OSCs) with solution-processable titanium (diisopropoxide) bis(2,4-pentanedionate) (TIPD) as an electron extraction layer; this process was shown without thermal annealing treatment. The power conversion efficiency (PCE) is quite low in the initial stage, though it dramatically increases following constant light illumination and reaches a saturated state after 9 min of light illumination. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and ultraviolet photoemission spectroscopy (UPS) were used, and they showed that the TIPD molecules decomposed and formed stable Ti O bonds. According to photocurrent density-effective voltage curve (J ph - V eff), short-circuit current density (J SC) and open-circuit voltage (V OC) value under different light intensity, the photo-annealed TIPD-based OSCs showed efficient charge transport and suppressed charge recombination. Thus, after a fresh TIPD solution was spin-coated onto the indium tin oxide (ITO) surface and photo-annealed for 9 min, the OSCs showed the highest photovoltaic performance compared to ZnO-based OSCs. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Calcium (Ca) is not a desirable candidate as electron extraction layer (EEL) for long-term stability organic photovoltaics (OPVs) on account of its nature of active metal. In this paper, we has selected thieno[3,4-b]thiophene/benzodithiophene (PTB7) and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) as donor and acceptor, respectively, and the device architecture is Glass/ITO/poly(ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS)/PTB7:PC71BM/EEL/Aluminum. For comparison, tris (8-hydroxyquinoline) aluminum (Alq3) and Ca were used as EEL to reveal their influence on the performance [power conversion efficiency (PCE), short-circuit current density (J SC), open-circuit voltage (V OC) and fill factor (FF)] of the OPVs. As a result, PCE of the device with Ca as EEL rapidly reduced over 60% after three days due to the poor stability of Ca. The device with Alq3 as EEL shows favorable stability owing to the PCE moderate declined less than 30% after one month. Furthermore, PCE of the device with Alq3 as EEL was fully comparable to that with Ca as EEL. Our results indicate that Alq3 is an alternative candidate for high-performance and long-term photo-stability OPVs. [Copyright &y& Elsevier]

Photo-annealing treatment titanium chelate (TIPD) layer, which was the indium tin oxide (ITO) interface-modified layer, was used as a replacement for the thermal annealing treatment of TIPD. The power conversion efficiency (PCE) of photo-annealed TIPD-based polymer solar cells (PSCs) is quite low in the initial stage, but it dramatically increases following constant light illumination, and the cell achieves a saturated state after 9 min of light illumination. By employing the mixed films poly[1-(5-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)-6-methylbenzo[1,2-b:4,5-b′]dithiophen-2-yl)thiophen-2-yl)-5,7-bis(2-ethylhexyl)-3-(5-methylthiophen-2-yl)-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione] (PBDB-TF) and 2,2′-((2 Z ,2′ Z)-(((4,4,9,9-tetrakis-(4-hexylphenyl)-4,9-dihydro-sindaceno[1,2- b :5,6- b ']-dithiophene-2,7-diyl)bis(4-((2-ethylhexyl)oxy)thiophene-5,2-diyl))bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene)) dimalononitrile (IEICO-4F) as photoactive layers, we improved the photovoltaic performance. The enhanced photovoltaic performance of TIPD films treated with photo-annealing was explained by the increased short-circuit current density (J SC). Efficient medium- and long-wavelength light transmittance and suppression of charge recombination are beneficial for enhancing the J SC value. • Titanium chelate (TIPD) films by photo annealing treatment is efficient electron extraction layer (EEL) material. • The photo annealing treatment TIPD films achieve efficient charge transport and weak charge recombination. • The efficient medium and long wavelength light transmittance efficiency for photo annealing TIPD films. [ABSTRACT FROM AUTHOR]

Abstract: Solution-processable functionalized graphene (SPFGraphene) and functionalized multiwalled carbon nanotubes(f-MWCNTs) are introduced for heterojunction solar cell. The performance of the device has improved by the incorporation of both SPFGraphene and f-MWCNTs. The open-circuit voltage (V oc), short-circuit current density (J sc), fill factor (FF) and power conversion efficiency (η) were 0.67V, 4.7mA/cm2, 32%, and 1.05%, respectively. Here, we expect that SPFGraphene acts as exciton dissociation and provide percolation paths for electron transfer, whereas f-MWCNTs provide efficient hole transportation. SPFGraphene and f-MWCNTs incorporation yields better carrier mobility, easy exciton splitting, and suppression of charge recombination, thereby improving photovoltaic action. [ABSTRACT FROM AUTHOR]

In this study, a ternary polymer solar cell (PSCs) are fabricated by using two well-compatible donors as a blend donor (D18 as the host donor and PBDB-TF as the guest donor) and Y6 as an acceptor. The D18:Y6 and PBDB-TF:Y6 binary PSCs exhibit 13.96% and 13.42% power conversion efficiencies (PCEs), respectively. D18 and PBDB-TF have similar highest occupied molecular orbital (HOMO) energy levels, which prevents the formation of charge recombination centers within photoactive layer. The increased short-circuit current density (J SC) is mainly attributed to the complementary absorption spectra of PBDB-TF to that of D18 and Y6. In addition, the cascade lowest unoccupied molecular orbital (LUMO) energy levels of D18 and PBDB-TF lead to improved exciton dissociation and charge transport at the D18/PBDB-TF interface. The optimized ternary PSCs show highest PCE of 14.85%. Such ternary strategy with two well-compatible donors with similar HOMO energy levels and cascade LUMO energy levels is an efficient method to realize performance improvement of PSCs. [Display omitted] • Ternary PSCs were fabricated with PBDB-TF as third component materials. • The improvement of charge dynamics process by ternary strategy. • The improved exciton-dissociation at the donor–blend acceptor interface. • The ternary PSCs with blend donor achieved a PCE of 14.85%. [ABSTRACT FROM AUTHOR]

Photocatalytic overall water splitting (POWS) is a promising route for converting solar energy into green and sustainable energy. Herein, we report a facile hydrothermal approach to fabricate polyhedron BiVO4 by Mo and Yco-doping (MYB) photocatalysts with suitable band gap for POWS. The MYB exhibited enhanced visible light-driven POWS activities in comparison with that of as-prepared BiVO4, Y-BiVO4 and M-BiVO4, with the maximum H2 and O2 evolution rate of 34.7 and 17.4 μmol·h−1·g−1, respectively. The optimum activity of the catalyst was controlled by adjusting Mo content of MYB. The photodeposition of Pt shows that there are special separation reduction and oxidation centers on the surface of MYB. Electrochemical experiments further confirmed the enhanced charge separation of MYB. MYB photocatalyst has small particle size, unique polyhedral structure, large specific surface area and high (103) and (200) surface exposure, thus improving POWS performance, high electron transfer efficiency and effective separation of photogenerated electron–hole pairs. Because of the doping of Mo and Y elements, the electronic structure of the catalyst is altered, enhancing light absorption and reducing the recombination of photogenerated electron–hole pair. The current study revealed that the MYB products could serve as cost-effective and stable photocatalysts for POWS. [ABSTRACT FROM AUTHOR]

Ternary blend films, obtained by introducing a third component (a second acceptor as the third component) to a binary polymer solar cell (PSC), are a promising ternary strategy because the light absorption range, surface morphology, and charge carrier transport of the photoactive layer may be optimized, as can the energy level alignment between the donor and the acceptor. In this work, acceptors such as the short-wavelength-absorption polymer N2200 and the long-wavelength-absorption small molecule FOIC were combined with the donor PBDB-T-2F to construct ternary blends. The optimized ternary PSC could achieve a power conversion efficiency (PCE) of 13.98%, which is higher than the efficiencies of binary PSCs based on PBDB-T-2F:FOIC (12.65%) and PBDB-T-2F:N2200 (9.36%). The enhanced PCE of the ternary PSC is based on the high electron mobility, balanced charge transport, optimized surface morphology and charge carrier kinetics and the extended light absorption of the ternary photoactive layer, realized by adjusting the ratio of FOIC:N2200. Our results indicate that mixing a polymer acceptor into a binary photoactive layer to form a ternary blend photoactive layer is a valuable strategy for improving photovoltaic performance. Image 1 • Ternary PSCs were fabricated with F–N2200 as third component materials. • The improvement of charge dynamics process of ternary photoactive layer by ternary strategy. • The improved photon harvesting at the donor–blend acceptor interface. [ABSTRACT FROM AUTHOR]

Planar-structure perovskite solar cells have attracted more and more attention, because their simple and low-temperature preparation processing. However, the performance of perovskite solar cells is currently limited by defect-induced recombination at interfaces between perovskite and charge transport layers. In this work, a filmy poly methyl methacrylate (PMMA) layer introduced in Perovskite/Spiro-OMeTAD interface to passivate the interfacial and interganular defects, by which a high open-circuit voltage (1.18 V) is acquired, and the optimal device shows a steady-state power conversion efficiency of 20.5% and negligible hysteresis. Femtosecond transient absorption measurement confirms a significant reduction in non-radiative recombination for passivated devices. Mott-Schottky measurement indicates improved flat band potential and carrier density in passivated devices, consisting with the increased voltage. In addition, PMMA film can protect perovskite film from moisture and oxygen erosion. The unsealed device still maintains 95% of the initial efficiency under ambient conditions with 60% relative humidity for one month. This approach solves one of the main limitations of interfacial recombination and shows its potential to improve the performance of perovskite solar cells in the future. • An ultrathin polymer film is used to passivate the interfacial and intergranular defects in PSCs. • The modified PSC shows a steady-state power conversion efficiency of 20.5% and negligible hysteresis. • The fs-TA measurement is implemented for analyzing transfer and recombination dynamics of the photo-generated carrier. • The PMMA film plays the role of encapsulation which could protect perovskite film from moisture and oxygen erosion. [ABSTRACT FROM AUTHOR]

The ternary organic solar cells (OSCs) were fabricated with PBDB-T as donor and a blend of IEICO-4F and NC 70 BA as the acceptor and the power conversion efficiency (PCE) reaches 10.92%. Due to good compatibility and cascade LUMO level among PBDB-T, a large amount of IEICO-4F and a small amount of NC 70 BA (the ratio of IEICO-4F:NC 70 BA is 85:15), which beneficial for adjusting lowest unoccupied molecular orbital (LUMO) levels of blend acceptor and wide energy offset between the donor and acceptor materials, leading to the enhancement of the open-circuit voltage (V OC). The optimized ternary PBDB-T:IEICO-4F:NC 70 BA films is more efficient exciton dissociation and suppress charge carrier recombination than that of binary PBDB-T:IEICO-4F and PBDB-T:NC 70 BA films, leading to small energy losses. In addition, this approach maintains PCE without sacrificing short-circuit current density (J SC) and fill factor (FF), even if the weak long and near-infrared wavelength photon harvesting. A more than 10% PCE improvement is achieve by employing a ternary strategy in comparison to PBDB-T:IEICO-4F-based binary OSCs with a PCE of 9.87%. Simultaneously, the optimized ternary PBDB-T:IEICO-4F:NC 70 BA OSCs exhibit the excellent thermal stability and 78.8% initial PCE under thermal annealing treatment at 80 °C for 20 h. • The ternary OSCs with blend acceptor achieved a PCE of 10.92%. • Around 10% PCE improvement is obtained by employing ternary strategy. • The improvement of exciton-dissociation at the Donor/blend acceptor interface. • The simultaneously enhance performance and stability for ternary OSCs. [ABSTRACT FROM AUTHOR]

Fullerene‐free organic solar cells (OSCs) are fabricated using a blend of J61 polymer as donor and the blend of m‐3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexyl phenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′] dithiophene (ITIC) and ITIC‐Th as electron acceptor. The blend of m‐ITIC and ITIC‐Th as electron acceptor due to the similar lowest unoccupied molecular orbital energy levels and good compatibility among J61, m‐ITIC, and ITIC‐Th, are beneficial for the small energy barrier at the m‐ITIC:ITIC‐Th interface. Simultaneously, the ternary photoactive layer can maintain the optimize film morphology and beneficial to ensure effective suppression of charge recombination at the three kind materials interface. The power conversion efficiency of ternary OSCs achieves to 12.57% when the blend of m‐ITIC:ITIC‐Th (the ratio of m‐ITIC:ITIC‐Th is 40:60) as electron acceptor, with enhanced open‐circuit voltage (VOC) of 0.91 V, short‐circuit current densities (JSC) of 19.94 mA cm−2, and fill factor of 69.6%. Moreover, the optimal ternary OSCs show enhanced thermal stability and photostability than the binary OSCs. This study indicates that the blend of m‐ITIC and ITIC‐Th as electron acceptor and J61 as donor is a promising strategy to fabricate high performance and stable OSCs. [ABSTRACT FROM AUTHOR]

Ternary polymer solar cells (PSCs) are fabricated that consisted of a blend of IEICO‐4F and 3TT‐FIC as electron acceptors and PBDB‐T as an electron donor. The power conversion efficiency (PCE) of ternary PSCs is increased from 9.9% to 11.22% via the blend of IEICO‐4F and 3TT‐FIC as electron acceptors (the ratio of IEICO‐4F:3TT‐FIC is 6:4), which enhances the open‐circuit voltage (VOC) from 0.71 to 0.78 V. The main contribution of the blended acceptor is its broad energy level offset between the donor and acceptor (from 1.26 to 1.30 eV) due to the enhanced lowest unoccupied molecular orbital energy levels of the blended acceptor. Meanwhile, the small energy losses of the ternary photoactive layer (reduced from 0.55 to 0.52 eV) are simultaneously due to the more efficient exciton dissociation and the suppressed charge carrier recombination. This work provides an effective strategy for improving the photovoltaic performance of binary PSCs. [ABSTRACT FROM AUTHOR]

Wide‐bandgap CsPbCl3 perovskite has fueled studies on applications in a variety of newly developing optoelectronic devices, including solar cells, lasers, light‐emitting diodes, and photodetectors. Most of them are now focused on film fabrication and device performance optimization, technology transfer of these proof‐of‐concept devices to the market will necessitate optimization of the device structure to minimize the optical loss and fabrication cost. While device model‐based electro‐optics simulations are considered a powerful method to attain the purpose, during which accurate optical constants are preconditions. Herein, for the first time, the optical constants of CsPbCl3 film through Mueller matrix spectroscopic ellipsometry (SE) are reported. Taking optoelectronic devices in vertical structure as a demonstration, simulations on the distributions of 2D electromagnetic field and photo‐generated electron field are arranged, successfully demonstrating the profile of the photons and electrons inside the devices. The evolution trend of device performance in the experiments matched with the simulations, for device performance is closely related to the photons and photo‐generated electrons. Benefitting from the simulations and experiments, general design criteria of the CsPbCl3‐based optoelectronic and photonic devices are posed, inevitably accelerating their development and commercialization. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells (PSCs) such as inverted PSCs are gaining increasing attention due to their wide range of potential applications, while the selection of stable, high conductivity and energy level suitable hole transport layers (HTLs) is still challenging. Here we introduce dopant-free copper phthalocyanine (CuPc) as HTL in inverted planar PSCs, and demonstrate improved photovoltaic performance and increased stability with high reproducibility and uniformity compared to the PEDOT:PSS based devices. The champion efficiency of PSCs is achieved by 15.4% on rigid substrates and 12.8% on flexible substrates, respectively. The flexible devices also exhibit excellent bending stability, retaining ∼85% of the original power conversion efficiency (PCE) after 3000 bending cycles at r = 5 mm without encapsulation. Our study provides a new strategy for fabricating cost-effective, scalable and flexible PSCs with high efficiency, little hysteresis, and excellent stability. [ABSTRACT FROM AUTHOR]

SnO 2 electron transport layers (ETLs) had an essential role in the n-i-p structure of perovskite solar cells. Improving the quality of the electron transport layer and enhancing interfacial contacts were key factors in the fabrication of high-performance perovskite solar cells. Therefore, a non-ionic polymeric polyacrylamide (PAM) modified SnO 2 colloidal solution with improved clustering of SnO 2 nanoparticles was presented to form a uniform and dense SnO 2 electron transport layer. The results demonstrated that no pinhole pores were found at the interface where the PAM-modified electron transport layer and the light absorbing layer came into contact, a structure that facilitated carrier transport and reduced carrier recombination at the interface location. Further beneficial effects were revealed by femtosecond Fs-TA measurements and trap of states (tDOS) analysis, where the carrier lifetime τ 2 decreased from 306.7 ps to 137.8 ps and the trap density of states of the film also decreased significantly. Correspondingly, the SnO 2 -PAM device exhibited an optimum efficiency of 21.61 %. Fantastic device stability was obtained due to the interaction of excellent contact at the SnO 2 /FAPbI 3 interface, and 85 % of the initial efficiency was maintained when placed in air for 1000 h for photo-aging tests, thereby improving the stability of FAPbI 3 grains. This method of improving the quality of tin oxide colloidal solutions provided a novel and simple way to prepare efficient perovskite solar cells. [ABSTRACT FROM AUTHOR]

CsPbIBr 2 perovskite, as a promising light harvester, possesses the most balanced bandgap and stability characters among all-inorganic perovskite materials. However, the poor quality of the traditionally one-step solution-processed CsPbIBr 2 film always leads to a severe recombination loss and thus a low output potential difference (V oc). Herein, we demonstrate a novel vapor-assisted deposition strategy to construct high-quality CsPbIBr 2 films for the first time, in which the crystallization kinetics of the CsPbIBr 2 is more easily controllable than that of the one-step spin-coated one. The PbBr 2 film acting as the template in the CsPbIBr 2 crystal growth is firstly prepared via an antisolvent-washing technique and CsI is then vacuum evaporated onto the PbBr 2 layer. By precisely tuning the thickness of the CsI film, highly phase-pure and crystallized CsPbIBr 2 crystals are successfully obtained. The optimized CsPbIBr 2 film also exhibits a homogeneous morphology and full coverage over the substrate with large grain sizes up to microscale and ultrahigh light absorption capability. The corresponding carbon-based CsPbIBr 2 solar cells achieve a champion power conversion efficiency of 8.76% with a superior V oc of 1.289 V. The large-area (1 cm2) devices also deliver an efficiency of 6.78% with an impressive V oc of 1.336 V. Moreover, under the protection of the highly hydrophobic and chemically stable CuPc layer and carbon counter electrode, the unencapsulated devices present excellent moisture and thermal stabilities. Our work provides a new approach for the preparation of cost-effective, highly efficient and robust CsPbIBr 2 photovoltaics. Vapor-assisted deposition of CsPbIBr 2 films for highly efficient and stable carbon-based planar perovskite solar cells with superior V oc are demonstrated. A champion PCE of 8.76% with an superior V oc of 1.289 V as well as excellent moisture and thermal stabilities are achieved. Image 1 • A novel and facile vapor-assisted deposition method is developed to fabricate CsPbIBr 2 perovskites for the first time. • Highly phase-purity and crystallized CsPbIBr 2 films with large grain sizes are obtained. • A high PCE of 8.76% with a superior V oc of 1.289 V is achieved. • A PCE of 6.78% with an impressive V oc of 1.336 V is gained for the large-area (1 cm2) devices. • Excellent moisture and thermal stabilities are obtained for our devices. [ABSTRACT FROM AUTHOR]

Enhancing the optical, morphological and electronic properties of the solution-processed CsPbIBr 2 films by lithium doping for efficient carbon-based perovskite solar cells is demonstrated. The champion PCE of the CsPbIBr 2 cells is boosted from 7.41% to 9.25%, showing an increase by 24.8%. • A novel Li doping method is developed to enhance the morphological and electronic properties of the CsPbIBr 2 films. • The champion PCE of the carbon-based CsPbIBr 2 PSCs is boosted from 7.41% to 9.25% by 4% Li-doping. • Excellent moisture and thermal stabilities are obtained for the as-fabricated device. CsPbIBr 2 perovskite exhibits the most balanced bandgap and durability features among all the inorganic perovskites, showing great potential in the photoelectric field. Nevertheless, the poor film quality of the traditionally spin-coated CsPbIBr 2 restricts the further improvement of the device performance. Here, we develop a novel lithium (Li) doping strategy to promote the optical, morphological and electronic properties of the solution-processed CsPbIBr 2 perovskites. Upon incorporating Li+ ions into CsPbIBr 2 lattice, highly crystallized and well-oriented CsPbIBr 2 crystals are obtained. The as-prepared Li-doped CsPbIBr 2 exhibits a higher film coverage over the substrate with larger grains and less grain boundaries compared to the none-doped counterparts. The trap-state densities in the CsPbIBr 2 film are also effectively alleviated while the carrier lifetimes are elongated by Li doping, contributing to a lower energy loss and a higher charge collection efficiency. The optimized Li-doped perovskite solar cells (PSCs) demonstrate an excellent champion power conversion efficiency (PCE) of 9.25%, much higher than that of the none-doped devices (7.41%). Furthermore, the unencapsulated devices present a superior air and thermal stability under the protection of the hydrophobic CuPc layer and carbon electrode. Our work provides a new opportunity to fabricate cost-effective and highly efficient CsPbIBr 2 PSCs in a facile way. [ABSTRACT FROM AUTHOR]

All-inorganic CsPbBr 3 perovskite has triggered great interests in photovoltaic field owing to its superior stability. However, the uncontrollable CsPbBr 3 film growth in solution always leads to a poor film quality with low phase-purity as well as many surface and bulk defects. Herein, we demonstrate an environmentally friendly non-solution route to fabricate high-quality CsPbBr 3 films for carbon-based planar perovskite solar cells. By precisely tuning the thickness ratio of the evaporated CsBr to PbBr 2 precursors (r), the dominant phase conversion of the cesium lead bromide perovskites from PbBr 2 -rich CsPb 2 Br 5 (r ≤ 12:7) to CsPbBr 3 (r = 12:8), and further to CsBr-rich Cs 4 PbBr 6 (r ≥ 12:9) are achieved. The optimized CsPbBr 3 perovskites are highly phase-pure and crystallized with ultra-high light absorption ability. The as-prepared CsPbBr 3 films also exhibit a dense and uniform morphology with large grain sizes and monolayer-vertical aligned grains. The corresponding devices deliver a champion PCE of 7.58%, which is an excellent efficiency among carbon-based CsPbBr 3 cells with evaporated CsPbBr 3 light absorbers. The large-area (1 cm2) devices also achieve an efficiency of 6.21%. Moreover, the unencapsulated CsPbBr 3 devices present superior moisture and thermal stabilities. Our work provides a facile approach to fabricate high-quality and large-area CsPbBr 3 films for highly efficient solar cells, light-emitting diodes and photodetectors. Image 1 • A sequential evaporation method is devised to prepare high-quality CsPbBr 3 films. • An excellent PCE of 7.58% is achieved for carbon-based CsPbBr 3 PSCs. • A PCE of 6.21% is obtained for large-area devices with an active area of 1 cm2. • Superior moisture and thermal stabilities are obtained for the devices. • The whole production costs of the devices are very low. [ABSTRACT FROM AUTHOR]

Photoelectrocatalytic (PEC) water splitting technology is used to convert solar energy into hydrogen energy, and has the potential to alleviate energy crisis problem. TiO2 nanowire arrays (NAs), as a promising PEC photoanode, have the advantages of low cost and stable mechanical properties. However, due to its wide energy band, poor conductivity, and slow carrier transfer kinetics, modifying TiO2 NAs with metal is a feasible way to achieve high PEC performance, especially cobalt-based compounds. Different from the fussy and polluted synthesizing methods, here, we use a facile method to successfully load Co3O4 and CoO mixtures on TiO2 NAs. A series of characterization methods are conducted to study the morphology, structure, and PEC water oxidation performance. It is found that the photocurrent density of the obtained CoO-Co3O4/TiO2 photoelectrode is enhanced and good stability can be kept up for 13 h or more. The prominent reason for enhanced PEC performance of CoO-Co3O4/TiO2 NAs is that loading CoO and Co3O4 can increase the light absorption, reduce the charge transfer resistance, and improve the charge separation efficiency of TiO2 NAs. Our work introduces an alternative designing way to load both of CoO and Co3O4 on photoelectrode in a particularly eco-benign way, which provides efficient and stable cobalt-based TiO2 photoanodes, and it can be applied to wider research fields, such as solar cells and photo-responsive devices. [ABSTRACT FROM AUTHOR]

In this experiment, the molybdenum oxide (MoO X ) layer were fabricated by spin-coated ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 -4H 2 O) solution and thermal annealing treatment. The MoO X layer is shown the deeper energy level, which is more match the highest occupied molecular orbital (HOMO) energy level of the donor. The effect of the thermal annealing of the MoO X layer on hole mobility and photovoltaic performance was investigated. It was found that the 16 nm thick MoO X layer has the best hole mobility and photovoltaic performance as a HEL device. From the space charge limited current (SCLC) and time of flight (TOF) curve, the MoO X layer has shown the better hole extract and transport ability compared with polyethylenedioxy-thiophene:polystyrenesulfonate (PEDOT:PSS, Clevios Al4083) layer. The photocurrent density versus effective voltage ( J ph  −  V eff ) curve, short-circuit current ( J SC ) and open-circuit voltage ( V OC ) value dependent on incident light intensity is confirmed that the weaken charge carrier recombination of MoO X -based PSCs at the open circuit condition and short circuit condition. After prolonged light illumination (during ten days), the MoO X -based PSCs is shown the better photo-stability compared with PEDOT:PSS-based PSCs and the similar decrease ratio compared with inverted PSCs. [ABSTRACT FROM AUTHOR]

α-Formamidinium lead iodide (α-FAPbI 3) has become one of the most promising candidate materials for stable perovskite solar cells (PSCs) owing to their outstanding optoelectronic properties and high thermal stability. The crystallinity of the active layer of perovskite is essential to the performance of perovskite solar cells. In this paper, we added lead acetate Pb(Ac) 2 as a grain growth agent into the perovskite precursor solution to prepare high-efficiency and stable perovskite solar cells. It was revealed that the crystals of Pb(Ac) 2 -modified film grew selectively along the [200] direction and that the FAPbI 3 active layer grains were arranged neatly and densely, due to the significant influence of a moderate amount of weakly acidic Ac- on the crystal growth of FAPbI 3. The relative reduction in its grain boundaries led to the decrease in the grain boundary impedance, and it was easier for electrons to perform long-range migration in the perovskite active layer. The beneficial effects of Pb(Ac) 2 were further expiored by femtosecond Fs-TA measurements and density of states (tDOS) analysis, where the carrier lifetimes τ 2 was increased from 482.4 ps to 1340 ps, and the trap density of film states was significantly reduced. The filling factor (FF) and power conversion efficiency (PCE) were increased from 76.5% and 19.7–81.1% and 21.8%, respectively, the Pb(Ac) 2 devices were placed in air for 800 h for the light aging test, and the test results still maintained 90% of the original efficiency, which improved the stability of FAPbI 3 crystals. • Pb(Ac) 2 as an additive to modulate the crystalline quality of perovskite active layer films. • Perovskite solar cell defect reduction and carrier lifetime increase by Pb(Ac) 2 modification. • The Pb(Ac) 2 -modified active layer grains have preferential orientation and orderly arrangement. • 81.1% filling factor and 21.8% efficiency are achieved for a single PSC cell with excellent stability. [ABSTRACT FROM AUTHOR]

ZnS as an inorganic passivation agent has been proven to be effective in suppressing charge recombination and enhancing power conversion efficiency (PCE) in quantum dot-sensitized solar cells (QDSCs). In the present study, we constructed a novel TiO2/ZnS/CdS/ZnCdS/CdSe/ZnS photoelectrode via successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD). The complementary effects of multi-ZnS layers on the optical and electrochemical performance of the QDSCs were systematically investigated. The multi-ZnS can not only facilitate the growth and distribution of QDs, but also suppress the different interface charge recombination effectively. We suggest that the formation of the ZnCdS intermediate layers via ion-exchange route during CBD process contributes to the higher photoelectrochemical cell performance of the QDSCs with the middle ZnS layer. When the three-layer ZnS was employed in CdS/CdSe co-sensitized system, the PCE reached 6.05%, which is much higher than that observed for solar cells with the conventional single ZnS treatments and the two layers inserted at the interface between CdS QDs and CdSe QDs and electrolyte (4.80% and 5.42%, respectively). [ABSTRACT FROM AUTHOR]

The development of perovskite solar cells has improved rapidly. However, PSCs generally suffer from instability, due to the detrimental defects. Additive engineering is a favorable method for defect passivation. In this work, the linear pseudo-halogen salt, KSCN, is introduced into the MAPbI 3 perovskite film to improve the performance of PSC. The trap density of cells with SCN− is decreased significantly. The SCN− not only can fill halogen vacancies to reduce the halide-related defects, but also can interact with the uncoordinated Pb2+ via coordinate bond to stabilize perovskite lattice structure. Moreover, the performance of devices with other linear pseudo-halogen anions (OCN−, SeCN−) are also investigated. Due to the improved short circuit current density, the power conversion efficiency of devices increases from 18.02% (PVK) to 20.41% (PVK–SCN-), 19.53% (PVK–OCN-) and 19.23% (PVK–SeCN-), respectively. After introducing pseudo-halide anions, the devices showed robust stability under the ambient environment. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid perovskite materials with distinctive optoelectronic properties have attracted much interest in the field of solar cells. As the light absorber, the quality of perovskite films is crucial to the performances of perovskite solar cells. Anti-solvent engineering seems to be an efficient method in preparing high-quality perovskite films, but mostly used anti-solvents are toxic, such as chlorobenzene (CB)， which is harmful to the environmental protection. In the present work, we used the green anti-solvent diethyl carbonate (DEC) instead of CB, demonstrated that the DEC engineered CH 3 NH 3 PbI 3 film exhibits improved morphology and crystallinity as well as reducing defects, which can be attributed to the interaction between DEC and the solvent dimethyl sulfoxide (DMSO). The DEC anti-solvent assisting yields efficient CH 3 NH 3 PbI 3 perovskite solar cells with a champion power conversion efficiency of 20.20% and a steady state efficiency of 86% over a period of 20 days of storage under ambient conditions. The present study provides a viable path way to design green and effective perovskite solar cells in the future. [Display omitted] • Developed a green solvent-assisted perovskite crystallization method. • Formed uniform and compact perovskite films with large grains. • High-quality perovskite films prepared by green anti-solvent diethyl carbonate. [ABSTRACT FROM AUTHOR]

The possible exhaustion of fossil fuels in the near future and soaring global energy demand have driven the search for new types of sustainable and renewable alternatives. Perovskite (CHNHPbX, X = I, Br, Cl) solar cells are a type of solar cell based on a perovskite absorber, most commonly a tin halide-based or hybrid organic-inorganic lead material, as the visible-light sensitizer layer, which produces electricity from sunlight. Recently, perovskite solar cells have received substantial worldwide attention. Compared with traditional solar cells, the perovskite solar cells can obtain high efficiency with a simple architecture and via a cost-effective process. In the latest 5 years, the efficiency of perovskite solar cells to convert power has skyrocketed from 3.8 % to more than 19.3 %. It is the fastest advancing solar technology to date. The highest efficiency demonstrated by perovskite solar cells is higher than that of dye-sensitized solar cells (DSSCs). A lager number of research groups have demonstrated that perovskite solar cells may ultimately boost efficiency as high as 25 %. The high efficiency and cheap production costs make it evident that perovskite solar cells have great potential to be commercialized soon. In this review, the history, materials, processing and architecture of solar cells are discussed to obtain a better understanding of high-performance perovskite solar cells. [ABSTRACT FROM AUTHOR]

Abstract: Herein we report a study of the doping of the poly(2-methoxy-5-(30,70-dimethyloctyloxy)-1,4- phenylenevinylene) (MDMO-PPV), poly (3-oc tylthiophene) (P3OT), to the organic photovoltaic devices based on poly (3-hexylthiophene) (P3HT) and graphene derivative bulk heterojunction structure (BHJ). The addition of the donor polymers to P3HT:Graphene BJT solar cells resulted in a more broad absorption range. The interrelationships between UV–vis absorption, fill factor (FF), energy conversion efficiency (ECE) and current density have been simulated. Dependency of the open-circuit voltage (Voc) was based on different doped donors, which is due to the band structure of BHJ where the energy level difference between the highest occupied molecular orbital (HOMO) of the co-donors and the lowest occupied molecular orbital (LUMO) of the solution-processable functionalized graphene oxide (SPFGO) as acceptor was increased. The investigation indicated that the ECE of the co-donors:SPFGO BHJ solar devices with moderate doped donor amount can be influenced by the change of molecular packing structure, which can be interpreted in terms of incorporating doped donor. The XRD investigation of the complex donors/graphene BHJ solar device showed a well-organized intraplane structure with lamellae oriented normal to the substrate. In addition, The SEM investigation indicated the surface roughness morphology of the hybrid active layer film. [Copyright &y& Elsevier]

Abstract: Characterization of a solution-processable functionalized graphene oxide (SPFGraphene oxide) was investigated by FT-IR spectroscopy and the result of elemental analysis showed that the isocyanate treatment results in the functionalization groups in SPFGraphene oxide. Doping SPFGraphene oxide to P3HT based solar cells induces absorbing spectra more strongly and a great quenching of the photoluminescence of the P3HT. With an increase in the SPFGraphene oxide content, the overall performances of the hybrid devices increases first, reaching the peak efficiency for the 10wt% SPFGraphene oxide content, and then decreases. After annealing at 160°C for different time durations, the device containing 10wt% of SPFGraphene oxide for 10min shows the best performance with a power conversion efficiency of 1.046%, an open-circuit voltage of 0.73V, a short-circuit current density of 3.98mAcm−2 and a fill factor of 0.36 under simulated AM1.5G conditions at 100mWcm−2; The similar content one for 20min shows η value of 1.013%, which is lower than the former one to a small extent for longer annealing duration. The graphene has the potential to act as the next-generation material in the photovoltaic devices and other applications for ease of preparation, low price, large surface area, high conductivity and excellent transparency. [Copyright &y& Elsevier]