Search

An exquisite, engineering of two poor hole transporting materials (HTMs, SnO, and PDTON) to form an excellent double‐layered HTL (SnO/PDTON) for inverted tin‐perovskite solar modules (TPSMs) is developed. SnO/PDTON has better photovoltaic performance than the commonly used PEDOT:PSS HTM when large‐area TPSMs are fabricated. Thermally evaporated SnO (that is a simple, available oxide with high hole mobility, good transparency, and adjustable frontier orbitals energy levels) film is used as a main hole transporting layer (HTL). Amphiphilic polymer PDTON (having the amine and ether groups on the side chains) film is used as a Co‐HTL, cross‐linker, passivator, and interface modification agent, as unveiled various physicochemical studies. Double‐layered SnO/PDTON with a flat morphology and good affinity toward perovskite precursor solution creates also a proper surface for depositing large‐area, high‐quality TPsk film. Therefore, TPSM (25.2 cm2 active area on 10 cm × 10 cm ITO substrate) based on double‐layered SnO/PDTON HTL achieving an efficiency over 10% with a negligible current hysteresis is reported for the first time. This study emphasizes not only the exquisite design of combining the specific characteristics of two prosaic HTMs to become a good double‐layered HTL but also gives a direction toward fabricating TPSMs to be applied in all‐perovskite tandem solar module. [ABSTRACT FROM AUTHOR]

Low‐temperature sol‐gel prepared ZnCo2O4 spinel‐based thin films are developed as high‐performance hole transporting layer (HTL) for coating perovskite film (NA‐Psk) from the basic MAPbI3/ACN/CH3NH2 solution in air without using anti‐solvent. Inverted PSC based on 2 mole% (vs Zn) Cu2+ doped ZnCo2O4 (2%Cu@ZnCo2O4) HTL and NA‐Psk absorber exhibit the maximum power conversion efficiency (PCE) of 20.0% with no current hysteresis while the cell based on ZnCo2O4 and PEDOT:PSS HTL (using NA‐Psk absorber) achieves the PCE of 15.79% and 12.3% with a current hysteresis index of 9.8% and 32.4%, respectively. Without encapsulation, PSCs based on 2%Cu@ZnCo2O4, ZnCo2O4, and PEDOT:PSS HTLs maintain 90%, 77%, and 12%, respectively of the original efficiency by standing in ambient atmosphere (temperature: 20–25 °C, RH:30%–40%) for 1800 h. Large area (10 cm × 10 cm substrate) perovskite mini‐module (PSM) with PCE over 15% is also demonstrated by using sol‐gel prepared 2%Cu@ZnCo2O4 HTL. The poor photovoltaic performance of PEDOT:PSS HTL is due to the basic MAPbI3/ACN/CH3NH2 solution will deprotonate the acidic PEDOT:PSS to reduce its conductivity whereas ZnCo2O4 HTL are not affected by basic perovskite precursor solution. [ABSTRACT FROM AUTHOR]

High-quality perovskite film is deposited on a 30 cm × 40 cm LiCoO2-coated ITO/glass via newly developed freely falling anti-solvent extraction (FFASE) method followed by post watervapor annealing in an ambient atmosphere. Perovskite solar modules (PSMs, active area of 25.2 cm2 with mask) based on this high-quality film achieve the highest efficiency of 16.04 and 30.76% under 1 sun (100 mW cm-2) and 945 lux fluorescent light illumination, respectively. The encapsulated PSMs are stable at -20 to 80 °C thermal cycling and keep high efficiency at temperature as low as -20 °C and as high as 80 °C. When the encapsulated PSM is heated at 85 °C and 85% relative humidity under room lighting or heated at 60 °C under AM1.5 (100 mW cm-2) illumination for 1000 h, loses only "8% of its original efficiency. The high stability of PSMs is due to very high quality perovskite absorber being used. The underlying concept of the FFASE method for extracting the solvent from the large-area perovskite precursor film is that the whole precursor film contacts with the fresh anti-solvent during the crystallization stage. [ABSTRACT FROM AUTHOR]

The oxide/nitride passivation and the flip‐chip package technology are developed for the perovskite solar cells. The heat resulting from the physical vapor deposition decomposes the active perovskite layer and degrades the efficiency of the perovskite solar cells down by more than 45%. Remarkably, with Si‐nitride passivation processed by plasma‐enhanced vapor deposition, the efficiency of the perovskite solar cell only decays about 9.1%. It is because that the plasma‐enhanced vapor deposition causes much less external energy on the perovskite solar cell. Using the exponential efficiency‐decay curves of the flip‐chip packaged perovskite solar cells, the characteristic time of the reliability‐tested solar cell can be calculated to be 145.8, 390.7, and 4864 h for air‐ambient, glove chamber, and water‐ambient tests, respectively. It is concluded that the concentration of O2(g) in the reliability test ambient is the root cause for the efficiency degradation of the perovskite solar cells. The low mobility of O2(g) under the water‐ambient reliability test results in the low probability of the adsorption of O2(g) on the surface of the flip‐chip package, which is the key factor for the least efficiency degradation of the perovskite solar cells among the three reliability tests. [ABSTRACT FROM AUTHOR]

A series of monochloro‐s‐triazinyl (MCT) and related m‐carboxypyridinium‐s‐triazinyl (nicotinic acid [NTR]) reactive dyes based on the same red chromophore and bearing –NHCN, –OCH3, –N(CH3)SO2CH3, –N‐methylphenyl and –OH "second‐leg" substituents were evaluated in cold pad‐batch dyeing. It was found that both the MCT and NTR dyes containing a cyanoamino second‐leg substituent displayed a superior technical performance to the dyes bearing methoxy, N‐methyl(methylsulphonyl)amino, hydroxyl and N‐methylaniline substituents. The results suggest that these technical benefits of dyeing are derived from the smaller molecule size and electronic effect of the cyanoamino group compared with the other second‐leg substituents commonly used in both MCT and NTR reactive dye synthesis. Indeed, the use of the cyanoamino second leg on the studied red NTR reactive dyes offered a combination of short batch time, high fixation efficiency, good build‐up properties and good wet fastness properties. [ABSTRACT FROM AUTHOR]

Room‐temperature‐processed TiO2 (R‐Lt‐TiO2) electron transporting layers (ETLs) possess low conductivity and connectivity, resulting in poor photovoltaic performance. Herein, an ethanol (EtOH)‐soluble, highly conducting fullerene derivative, C60RT6, was used as an additive for Lt‐TiO2 ETLs. Room‐temperature processed nanocomposite ETL (R‐Fu/Lt‐TiO2) is prepared simply by spin coating a C60RT6 and G‐TiO2 NPs (TiO2 nanoparticle prepared by grinding the bulk TiO2 powder) mixture. R‐Fu/Lt‐TiO2 has better aligned with the frontier orbitals of the FAxMA1−xPbI3, better continuity, conductivity, flatness, and higher surface hydrophilicity compared to Lt‐TiO2 ETL. Perovskite films spin coated on R‐Fu/Lt‐TiO2 ETLs also have slightly larger grains and thickness compared to those deposited on Lt‐TiO2. Perovskite solar cells (PSCs) based on a R‐Fu/Lt‐TiO2 ETL possess higher power conversion efficiency (PCE, up to 20% on glass substrate), less (negligible) current hysteresis, and better long‐term stability compared to those using R‐Lt‐TiO2 as an ETL. The flexible PSC (used indium tin oxide/polyethylene terephthalate (ITO/PET) as a substrate) with a R‐Fu/Lt‐TiO2 ETL achieves a PCE of 18.06% and retains 90% of the initial PCE after 500 bending cycles with a bending radius of 6 mm. The PCE of the flexible cell with a Lt‐TiO2 ETL is only 8.2%, and loses 60% of the initial value after 500 bending cycles. [ABSTRACT FROM AUTHOR]

The sequential deposition of a NiOx hole‐transporting layer, one‐step CH3NH3PbI3 perovskite absorber, and blended electron‐transporting layer that comprises [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) and PNDI(2OD)T2 via automated ultrasonic spray‐coating technique is demonstrated in air for planar inverted p–i–n solution‐processed perovskite solar cells. Films fabricated via laboratory‐sale spin‐coating and industrially compatible spray‐coating process, respectively, are compared with each other to optimize both the film‐coating quality and corresponding device performance. This is validated by the photovoltaic performance of prototype devices with three spray‐coated layers with the active area of 1 × 1 cm2. The champion cells achieve a power conversion efficiency of 10.09%, which is one of the highest efficiencies obtained from fully spray‐processed large‐area perovskite solar cells thus far. Furthermore, these results reinforce the feasibility of the spray‐coating methodology for the fabrication of multilayers within perovskite solar cells stack and low‐cost route toward upscaling the manufacturing alternatives to spin coating. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have received great attention due to their outstanding performance and their low processing costs. To boost their performance, one approach is to reinforce the built‐in electric field (BEF) to promote oriented carrier transport. The BEF is maximized by reinforcing the work function difference between cathode and anode (Δμ1) and increasing the work function difference between lower and upper surfaces of perovskite film (Δμ2) via introduction of electric dipole molecules, denoted as PTFCN and CF3BACl. The synergistic reinforcement of BEF improves charge transport and collection, and realizes markedly high photovoltaic performances with the best power conversion efficiency (PCE) up to 21.5%, a growth of 15.6% as compared to the control device, which is higher than the superposition of improvements achieved by either raising Δμ1 or Δμ2. Importantly, dual‐functional CF3BACl not only supplies dipole effect for tuning the surface potential of perovskite but offers hydrophobic trifluoride group toward the long‐term stable unencapsulated PSCs retaining more than 95% PCE after storing 2000 h under ambient conditions. This work demonstrates the synergistic effect of Δμ1 and Δμ2, providing an effective strategy for the further development of PSC in terms of photovoltaic conversion and stability. [ABSTRACT FROM AUTHOR]

A series of small‐molecule‐based hole‐transporting materials (HTMs) featuring a 4H‐cyclopenta[2,1‐b : 3,4‐b′]dithiophene as the central core with triphenylamine‐ and carbazole‐based side groups was synthesized and evaluated for perovskite solar cells. The correlations of the chemical structure of the HTMs on the photovoltaic performance were explored through different combinations of the central π‐bridge moieties. The optical and electrochemical properties, energy levels, and hole mobility were systematically investigated, revealing the significant influence of the central core planarity and packing structure on their photovoltaic performance. The optimized device based on CT1 exhibited a PCE (power conversion efficiency) of 17.71 % with a device architecture of FTO/TiO2 compact layer/TiO2 mesoporous/CH3NH3PbI3/HTM/MoO3/Ag, which was found to be on par with that of a cell fabricated based on state‐of‐the‐art spiro‐OMeTAD (16.97 %) as HTM. Moreover, stability assessment showed an improved stability for CPDT‐based HTMs in comparison with spiro‐OMeTAD over 1300 h. Four HTMs based on cyclopenta[2,1‐b;3,4‐b′]dithiophene core are designed and applied for lead perovskite (MAPbI3) solar cells. PSCs based on CT1 as HTM afford an impressive power conversion efficiency of 17.71 %. The devices based on the CT1 presented significantly higher stability than the device based on spiro‐OMeTAD. [ABSTRACT FROM AUTHOR]

The dye regeneration step in a dye‐sensitized solar cell (DSSC) affects significantly the device efficiency. To be able to predict the dye regeneration efficiency by the electrolyte this paper provides a facile way to design high‐efficiency sensitizers for DSSC. This paper proposes, for the first time, a simple and ingenious way to identify the dye regeneration sites and their relative efficiencies when a specific electrolyte is used. Two steps are proposed to identify the dye regeneration sites and their relative regeneration efficiencies: (1) drawing all the resonance structures of the oxidized dye to determine the regeneration sites, and (2) choosing the most favored site for dye regeneration as the chemically softest (when the redox couple used is soft I−/I3− pair) and the least spatially hindered site. The regeneration sites identified by the resonance structures are consistent with the β‐LUSO (β lowest unoccupied spin orbital) distribution, which is generally used for identifying the dye regeneration sites, calculated with DT‐DFT theory. The relative dye regeneration efficiency and photovoltaic performance of both ruthenium and metal‐free organic dyes predicted by the method reported here are supported by experimental data and the proposed dye regeneration mechanism. Several types of dye molecules are used to demonstrate the correctness of this new tool. This non‐classical tool, which uses the well‐known chemical knowledge of the resonance structure and hard–soft acid–base principle, without any computer calculation or physicochemical measurement, provides a very simple and powerful tool to quickly conceive high‐efficiency sensitizers for DSSCs. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) of the perovskite solar cell is high enough to be commercially viable. The next important issue is the stability of the device. This article discusses the effect of the perovskite grain-size on the long-term stability of inverted perovskite solar cells. Perovskite films composed of various sizes of grains were prepared by controlling the solvent annealing time. The grain-size related stability of the inverted cells was investigated both in ambient atmosphere at relative humidity of approximately 30-40 % and in a nitrogen filled glove box (H2O<0.1 ppm, O2<10 ppm). The PCE of the solar cell based on a perovskite film having the grain size larger than 1 μm ( D-10) decreases less than 10 % with storage in a glove box and less than 15 % when it was stored under an ambient atmosphere for 30 days. However, the cell using the perovskite film composed of small (∼100 nm) perovskite grains (D-0) exhibits complete loss of PCE after storage under the ambient atmosphere for only 15 days and a PCE loss of up to 70 % with storage in the glove box for 30 days. These results suggest that, even under H2O-free conditions, the chemical- and thermal-induced production of pin holes at the grain boundaries of the perovskite film could be the reason for long-term instability of inverted perovskite solar cells. [ABSTRACT FROM AUTHOR]

ABSTRACT Two D-π-A copolymers, based on the benzo[1,2- b:4,5- b′]-dithiophene (BDT) as a donor unit and benzo-quinoxaline (BQ) or pyrido-quinoxaline (PQ) analog as an acceptor (PBDT-TBQ and PBDT-TPQ), were designed and synthesized as a p-type material for bulk heterojunction (BHJ) photovoltaic cells. When compared with the PBDT-TBQ polymer, PBDT-TPQ exhibits stronger intramolecular charge transfer, showing a broad absorption coverage at the red region and narrower optical bandgap of 1.69 eV with a relatively low-lying HOMO energy level at −5.24 eV. The experimental data show that the exciton dissociation efficiency of PBDT-TPQ:PC71BM blend is better than that in the PBDT-TBQ:PC71BM blend, which can explain that the IPCE spectra of the PBDT-TPQ-based solar cell were higher than that of the PBDT-TBQ-based solar cell. The maximum efficiency of PBDT-TPQ-based device reaches 4.40% which is much higher than 2.45% of PBDT-TBQ, indicating that PQ unit is a promising electron-acceptor moiety for BHJ solar cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1822-1833 [ABSTRACT FROM AUTHOR]

Two fused-thiophene-containing ruthenium sensitizers, [Ru(Hdcbpy)(ottip)(NCS)2]- ·0.5[H]+ ·0.5[N(C4H9)4]+ [ Z1, H2dcbpy = 4,4′-dicarboxy-2,2′-bipyridine, ottip = 2-(5-octylthieno[3,2- b]thiophen-2-yl)-1 H-imidazo[4,5- f][1,10]phenanthroline] and [Ru(Hdcbpy)(odttip)(NCS)2]- ·0.5[H]+ ·0.5[N(C4H9)4]+ { Z2, odttip = 2-[6-octyldithieno(3,2- b:2′,3′)thiophen-2-yl]-1 H-imidazo[4,5- f][1,10]phenanthroline}, were designed for use in dye-sensitized solar cell (DSSC) applications. The fused-thiophene-based Z1 and Z2 have stronger light-harvesting capabilities compared with a non-fused-thiophene analog, [Ru(Hdcbpy)(otip)(NCS)2]- ·0.5[H]+ ·0.5[N(C4H9)4]+ [ JF-2t, otip = 2-(5-octylthiophen-2-yl)-1 H-imidazo[4,5- f][1,10]phenanthroline], and a standard N3 dye. The power-conversion efficiency of the Z1- and Z2-sensitized solar cells were superior (8.70 % and 8.15 %) to JF-2t- and N3-sensitized solar cells (7.85 and 7.40 %, respectively) under standard AM1.5G full sunlight irradiation. The photovoltaic performance of Z1 was better than Z2, primarily owing to the fact that Z1-based cells have a higher level of dye loading and less charge recombination, as seen from the electrochemical impedance spectroscopy data. This study not only demonstrates the excellent power-conversion efficiency of new fused-thiophene ruthenium sensitizers, but also points to the promise that fused-thiophene antennas might be a useful molecule in the engineering of ruthenium dyes for DSSCs. [ABSTRACT FROM AUTHOR]

A new class of hole-transport materials (HTMs) based on the bimesitylene core designed for mesoporous perovskite solar cells is introduced. Devices fabricated using two of these derivatives yield higher open-circuit voltage values than the commonly used spiro-OMeTAD. Power conversion efficiency (PCE) values of up to 12.11 % are obtained in perovskite-based devices using these new HTMs. The stability of the device made using the highest performing HTM ( P1) is improved compared with spiro-OMeTAD as evidenced through long-term stability tests over 1000 h. [ABSTRACT FROM AUTHOR]

A new heteroleptic ruthenium complex, coded CYC-B19, incorporating an ancillary ligand endowed with hexylthio-bithiophene segments and a conjugated anchoring ligand with vinyl groups was prepared. This new sensitizer exhibits a lower energy MLCT band centred at 562 nm with a remarkably high molar absorption coefficient of 2.97 × 104 M−1 cm−1. DFT-TDDFT theoretical calculation revealed that insertion a vinyl group in the anchoring ligand pushes the LUMO electron locating more on the anchoring ligand. This will benefit the electron transfer from dye to TiO2 when the dye molecules were excited by light. Physicochemical measurements and the optimization of electrolyte were done to investigate the potential of CYC-B19 in TiO2 scattering-layer free dye-sensitized solar cells. Not only is a good photovoltaic efficiency of 8.4% reached, but the transparent device sensitized by CYC-B19 also presents a superior spectral response to its predecessor CYC-B11. [ABSTRACT FROM AUTHOR]

Three unsymmetrical squaraines, where the electron-rich thiophene or bithiophene conjugated fragment was used to link unconventionally the squaraine core and carbazole (or methyl) group, were prepared. JYL-SQ1 with thiophene as a donor and indoline-carboxylic acid as an acceptor has λmax of 568 nm which is much longer than the general metal-free organic dyes. Adding a carbazole unit in JYL-SQ1 (forms JYL-SQ2) can red-shift the λmax to 603 nm. However, cabazole is not a strong donor (and indoline-carboxylic acid is a weak acceptor) the LUMO of all three dyes are delocalized majorly on squaraine unit: the excited electrons of dye molecules injecting into TiO2 are not so efficiency, resulting in low short-circuit current and conversion efficiency. The corresponding DSSC devices have the conversion efficiency of 0.71%, 2.59% and 2.22% for JYL-SQ1, JYL-SQ2 and THL-SQ3, respectively. [ABSTRACT FROM AUTHOR]

Seven new donor-spacer-acceptor metal-free organic dyes containing a fluorene and/or thiophene unit as a conjugated spacer are prepared and their physicochemical properties as well as photovoltaic performance are studied. The electron transfer from donor to acceptor upon excitation of these dyes is sensitive to the conjugated spacers. If a stronger donor moiety such as (ethylenedioxy)thiophene is used as a spacer, such as in F-E1 dye, the dye molecule has a better charge separation and therefore high efficiency. Furthermore, for the same donor and acceptor, fluorene is a better conjugated spacer than the bithiophene moiety because of its nonplanar conformation, which avoids the electron-hole recombination of dye upon photoexcitation. Short molecules with planar conformation aggregate easily, and the corresponding device reveals low open-circuit voltage Voc. On the other hand, dye molecules with long alkyl side chains (large size) adsorb less on the TiO2 electrode, which results in a smaller short-circuit current density Jsc. The difference in the efficiency of these dyes is small except for F-1 (owing to its short conjugation length), and electron density difference map analyses reveal that photoexcitation transfer of electron density from the donating moieties toward the acceptor/anchoring units occurs for all molecules. The small difference in the efficiency is attributed partly to the degree of effective charge transfer upon excitation, not totally to the absorption profile of the dye molecules. Furthermore, time-dependent DFT simulated absorption spectra are in excellent agreement with experimental spectra when the dyes are in their protonated states in THF solution. The transition probability calculated with the electron density difference analyses combined with the absorption data and photovoltaic performance provide useful information for designing organic sensitizers for dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

ABSTRACT An energy-economical dye-sensitized solar cell (DSSC) with highly flexible Ti/TiO2 photoanode was developed through a low-temperature process, using a binder-free TiO2 paste. Ti foils, coated with the binder-free TiO2 films were annealed at various temperature. Scanning electron microscopic (SEM) images of the films show uniform, mesoporous and crack-free surface morphologies as well as interpenetrated TiO2 network. DSSCs with binder-free TiO2 films annealed at 450, 350, 250 and 120°C show solar-to-electricity conversion efficiencies ( η) of 4.33, 4.34, 3.72 and 3.40%, respectively, which are comparable to the efficiency of 4.56% obtained by using a paste with binder and annealing it at 450°C; this observation demonstrates the benefits of a binder-free TiO2 paste for the fabrication of energy-fugal DSSCs. On the other hand, when organic binder was used in the TiO2 paste for film preparation, a drastic deterioration in the cell performance with decreasing annealing temperature is noticed. Laser-induced photo-voltage transient technique is used to estimate the electron lifetime in various Ti/TiO2 films. Electrochemical impedance spectroscopic (EIS) analysis shows that the lower the annealing temperature of the TiO2 coated Ti foil, the larger the charge transfer resistance at the TiO2/dye/electrolyte interface ( Rct2). Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) are one of the highly promising new‐generation photovoltaic technologies. One of the remaining challenges for commercializing PSCs is to prepare high‐quality, large‐area perovskite films in an ambient atmosphere reproducibly using less toxic materials. Herein, a nonvolatile, less toxic substance, 2‐pyrrolidinone (2P), is used as a complexant solvent for the perovskite precursor solution. Combining this with a newly developed spin‐assisted solvent extraction (SASE) crystallization method, a high‐quality perovskite film is prepared in air reproducibly. The nonvolatile nature of 2P and the formation of MAI–PbI2–2P adduct widen the time window for antisolvent engineering, and SASE enhances the solvent exchange rate of the precursor film to form a high‐quality perovskite film in air. An inverted cell (based on the postsolvent‐treated perovskite absorber) exhibits a power conversion efficiency of more than 18%. This film preparation method is feasible for depositing a high‐quality mixed‐cation or mixed‐cation, mixed‐halide perovskite film on both PEDOT:PSS and TiO2 surfaces to fabricate inverted and regular PSCs, respectively, to achieve efficiencies of more than 16%. More importantly, high‐quality, large‐area MAPbI3 film is prepared reproducibly in air for fabricating perovskite submodules to achieve an efficiency of 14% (verified at 13.04% after the cell is packed for efficiency evaluation). [ABSTRACT FROM AUTHOR]

From light to electricity: The inside cover picture illustrates the concept of designing hole transporting materials (HTMs) for perovskite solar cells. A subtle change of the central π‐bridge unit can lead to a significant improvement of device performance. In view of their excellent performance, the materials with two‐dimensional structural framework are promising HTMs for efficient and stable perovskite photovoltaic devices. More details can be found in the Full Paper by Yan‐Duo Lin et al. on page 307 in Issue 2, 2019 (10.1002/ente.201800939). [ABSTRACT FROM AUTHOR]