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Various isomers have been developed to regulate the morphology and reduce defects in state‐of‐the‐art perovskite solar cells (PSCs). To insight the structure‐function‐effect correlations for the isomerization of thiourea derivatives on the performance of the PSCs, we developed two thiourea derivatives [(3,5‐dichlorophenyl)amino]thiourea (AT) and N‐(3,5‐dichlorophenyl)hydrazinecarbothioamide (HB). Supported by experimental and calculated results, it was found that AT can bind with undercoordinated Pb2+ defect through synergistic interaction between N1 and C=S group with a defect formation energy of 1.818 eV, which is much higher than that from the synergistic interaction between two −NH− groups in HB and perovskite (1.015 eV). Moreover, the stronger interaction between AT and Pb2+ regulates the crystallization process of perovskite film to obtain a high‐quality perovskite film with high crystallinity, large grain size, and low defect density. Consequently, the AT‐treated FACsPbI3 device engenders an efficiency of 25.71 % (certified as 24.66 %), which is greatly higher than control (23.74 %) and HB‐treated FACsPbI3 devices (25.05 %). The resultant device exhibits a remarkable stability for maintaining 91.0 % and 95.2 % of its initial efficiency after aging 2000 h in air condition or tracking at maximum power point for 1000 h, respectively. [ABSTRACT FROM AUTHOR]

Tin‐based perovskite is a competitive analog with lead halide perovskite, but there are significant gaps in power conversion efficiency (PCE) and stability between tin‐ and lead‐based perovskite solar cells. The characteristics of the easy oxidizability of Sn2+ and the rapid crystal growth for tin‐based perovskite are two major issues remained to be overcome. Herein, an additive (4‐pyridylamidoxime (4‐PyAO)) with multiple functional groups is introduced in the perovskite precursor solution. The oxidation of Sn2+ and the crystallization rate of perovskite are both retarded by 4‐PyAO addition. The prepared perovskite film is of high quality with fewer trap states and carrier recombination, and carrier extraction and transfer between the perovskite film and the adjacent carrier transport layer also become more efficient. As a result, the corresponding devices deliver the highest PCE of 9.02%, accompanied by short‐circuit current density, open‐circuit voltage, and fill factor of 19.90 mA cm−2, 0.63 V, and 72.48%, respectively. More importantly, the best device without encapsulation maintains 92% of its initial PCE after 2500 h aging test in nitrogen atmosphere, which may be attributed to a synergic effect among the different functional groups. [ABSTRACT FROM AUTHOR]

Ultra‐thin stainless‐steel substrates with excellent water‐oxygen barrier properties and high thermal and electrical conductivities are suitable for the fabrication of lightweight and flexible perovskite solar cells (FPSCs). However, the deposition of dense perovskite films on stainless steel by the solution method is crucial because short circuits caused by perovskite holes are fatal to parallel structures. Herein, a single crystal (SC) is incorporated into the precursor solution to reduce the formation of holes in perovskite films on smooth stainless‐steel substrates. Additionally, a magnetic method is developed based on the properties of stainless steel to fix and fabricate FPSCs nondestructively on ultra‐thin stainless‐steel films with a thickness as low as 5 μm. Furthermore, 4,6‐dimethyl‐2‐mercaptopyrimidine (DMI) was introduced to passivate the surface of the perovskite film, optimizing the contact properties of the perovskite heterojunction and adjusting the energy level of the perovskite/C60 interface. Finally, ultra‐thin FPSCs achieved a champion power conversion efficiency (PCE) of 20.24% on an active area of 1.012 cm2 and a power‐to‐weight ratio over 3000 W kg−1. Moreover, under continuous illumination, the stainless‐steel substrates exhibited better photothermal stability than the polymer substrates. This method provides a basis for the fabrication of lightweight, low‐cost, and large‐area FPSCs. [ABSTRACT FROM AUTHOR]

Perovskite nanocrystals (NCs), such as MAPbX3 (MA+ = methylammonium; X = Cl, Br, or I), have received attention owing to their excellent optoelectronic properties and ease of integrating with flexible substrates. Lanthanide ion doping is widely used as an effective strategy to enhance the optoelectronic performance of perovskite NCs. However, incorporating the lanthanide dopant and ensuring the emission stability of the perovskite NCs in high‐performance optoelectronic devices remains a major challenge. Herein, the synthesis of Eu2+‐doped MAPbBr3 NCs within the channels of SBA‐15 is presented to improve their stability. The doped MAPbBr3 NC@SBA‐15 composites exhibit significantly improved stability than that of undoped MAPbBr3 NCs. The doped MAPbBr3 NC@SBA‐15 composites exhibit moderate PL quantum yields and excellent stability under ambient conditions and UV irradiation. In addition, the MAEu0.3Pb0.7Br3 NC@SBA‐15 composite applied in white‐light‐emitting diodes (WLEDs) achieves a color rendering index of 73.5. Moreover, MAEu0.3Pb0.7Br3 NC@SBA‐15 can be combined with styrene‐ethylene‐butylene‐styrene to fabricate a flexible direct X‐ray detector, realizing a high sensitivity of 7592.2 µC Gyair−1 cm−2 and a low detection limit of <77 nGyair s−1; this is an outstanding value for a NC‐based flexible direct X‐ray detector. This work serves as a guide for the design of perovskite NCs for both WLEDs and flexible X‐ray detectors. [ABSTRACT FROM AUTHOR]

Reducing the interfacial defects between the perovskite/electron transport layer (ETL) is the key point to improving the efficient and stable performance of perovskite solar cells (PSCs). In this study, two self-assembled molecules ((aminomethyl)phosphonic acid and glycine) with different functional groups (phosphonic acid (-H2PO3) and carboxylic acid (-COOH)) were mixed to form the buried bottom interface of PSCs. The synergistic effect of -H2PO3 with its higher anchoring ability and -COOH with its fast carrier transport improved the performance of PSCs. Additionally, the SnO2 modified by mixed self-assembly molecules (M-SAM) showed a more appropriate energy level alignment, favoring charge transport and minimizing energy loss. In addition, the amine group (-NH2) on the two small molecules effectively interacted with uncoordinated Pb2+ in perovskite and improved the quality of the perovskite films. Consequently, the (FAPbI3)0.992(MAPbBr3)0.008 PSCs with M-SAM reached a PCE of 24.69% (0.08 cm2) and the perovskite modules achieved a champion efficiency of 18.57% (12.25 cm2 aperture area). Meanwhile, it still maintained more than 91% of its initial PCE after being placed in nitrogen atmosphere at 25 °C for 1500 h, which is better than that of the single-SAM and control devices. Further reference is provided for the future commercialization of perovskite with efficient and stable characteristics. [ABSTRACT FROM AUTHOR]

All‐inorganic perovskite solar cells (PSCs) have been the research focus due to their high thermal stability and proper band gap for tandem solar cells. However, their power conversion efficiency (PCE) is still lower than that of organic‐inorganic hybrid PSCs. Herein, a sacrificing dye (Rhodamine B isothiocyanate, RBITC) is developed to regulate the growth of perovskite film by in situ release of ethylammonium cations, isothiocyanate anions and benzoic acid molecules upon annealing and illumination. The ethylammonium cations can efficiently passivate surface defects. The isothiocyanate anions incorporate with uncoordinated Pb to regulate the crystallization process. The benzoic acid molecules facilitate the nucleation of the perovskite crystals. Especially, the illumination can accelerate the release of these beneficial ions/molecules to improve the quality of perovskite films further. After optimization with RBITC, a high open circuit voltage (VOC) of 1.24 V and a champion PCE of 20.95% are obtained, which are among the highest Voc and PCE values of CsPbI3 PSCs. Accordingly, the operational stability of the PSC devices is significantly improved. The results provide an efficient chemical strategy to regulate the formation of perovskite films in whole crystallization process for high performance all‐inorganic PSCs. [ABSTRACT FROM AUTHOR]

The design of additives mainly involves selection of functional groups with coordination relationships with defects in perovskite materials. However, it is particularly important to further adjust the geometrical configuration and electronic structure of an additive. Here, the nicotinamide (NA) and its derivative 6‐Methylnicotinamide (CNA) with electron‐donor functional groups are comparatively analyzed to investigate the effect of molecular dipole and electronic configuration on the defect passivation of perovskite absorbers and the photovoltaic properties of perovskite solar cells (PSCs). Theoretical calculations demonstrate that the CNA molecule with its large molecular dipole combine with the undercoordinated Pb2+ ions in perovskite to form a higher binding energy, which is beneficial to improve the formation energy of Pb‐related defects. Experimental characterization confirms that the CNA molecule significantly enhances the coordination effect between acylamino and undercoordinated defective Pb2+ cations, which is conducive to obtain high‐quality, low‐defect density of state, large grain size, and smooth surface perovskite absorbers. Thanks to the electronic configuration and electronic cloud distribution of CNA molecules, the PSCs yield impressive efficiency as high as 24.33% with excellent environmental storage, heat, and light stabilities. This research provides a research basis for designing additives with steric‐charge‐dependence to assist perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

Perovskite solar cells have become stars in photovoltaics due to their rapidly increased efficiency. However, their stability is still below par due to moisture permeation from grain boundaries and defects. To conquer both problems at once, a passivation agent 3,4,5,6‐tetrafluorophthalicacid (TFPA) is rationally designed to heal both for not only improved cell efficiency but also better stability. It is found that the TFPA is prone to distribute along grain boundaries and has little influence within the bulk of the perovskite film. In addition, it appears that the TFPA helps to reduce the film roughness, to adjust the energy level, to facilitate hole transporting from perovskite to spiro‐OMeTAD, and to increase the hydrophobicity of the perovskite film, as it is demonstrated by the inhibited nonradiative recombination and prolonged carrier lifetime. Owing to strong interactions between F, ‐COOH, and Pb, the device with TFPA shows outstanding efficiency and stability. A perovskite solar cell with TFPA modification delivers a champion efficiency of 23.70% and a significantly enhanced stability that the device maintains 90% of its initial efficiency after 5200 h, among the best ambient stability. Herein, an effective strategy of grain boundary passivation is provided to improve the stability of perovskite solar cells. [ABSTRACT FROM AUTHOR]

As the efficiency of perovskite solar cell has skyrocketed to as high as 25.7%, their stability has become the biggest obstacle to commercialization. Preliminary analyses suggest that additive engineering may be effective in improving both solar cell efficiency and its stability. Herein, the plant‐derived natural green additive of l‐Theanine (Thea) is selected to improve the crystal quality of the perovskite absorber and obtain high‐performance perovskite solar cells (PSCs) with ultraviolet/ozone (UV/O3) resistance. The characterization results reveal that the CO group in Thea can effectively inhibit the precipitation of metal Pb0, passivate undercoordinated Pb2+ ions, and promote the nucleation and crystallization of perovskite. In addition, the combination of the NH group and I− in the form of a hydrogen bond cooperatively reduce the probability of nonradiative recombination of photogenerated carriers and effectively improves the extraction ability of carriers from perovskite absorber. With the cooperation of CO and NH2 groups in Thea, the champion efficiency is improved from 22.29% in the control device to 24.58%. More importantly, Thea significantly alleviates the perovskite phase transition and film decomposition induced by UV/O3 treatment. The study provides exploratory research for the application of plant‐derived green additives in the UV/O3 resistance field of perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

Effectively encapsulating perovskite solar cells (PSCs) to enhance the external reliability is the key towards commercialization. We herein propose a facile encapsulation method by introducing conductive ribbons and a polyethylene terephthalate (PET) backsheet on both sides of PSC. Via applying thermoplastic polyolefin (TPO) encapsulant, we implemented PSCs with fine encapsulation, enabling considerable durability in the ambient atmosphere and even with water immersion, demonstrating almost no degradation in the device output, which is ascribed to the low water vapor transmission rate as well as the high chemical stability of TPO. The operation reliability of the encapsulated cell is also significantly increased, maintaining 80% of the initial efficiency after 770 hours' light illumination in an ambient atmosphere. This novel encapsulation route provides a feasible idea for the commercial application of PSCs in the future. [ABSTRACT FROM AUTHOR]

Solar cell efficiency and stability are two key metrics to determine whether a photovoltaic device is viable for commercial applications. The surface termination of the perovskite layer plays a pivotal role in not only the photoelectric conversion efficiency (PCE) but also the stability of assembled perovskite solar cells (PSCs). Herein, a strong chelate coordination bond is designed to terminate the surface of the perovskite absorber layer. On the one hand, the ligand anions bind with Pb cations via a bidentate chelating bond to restrict the ion migration, and the chelate surface termination changes the surface from hydrophilic to hydrophobic. Both are beneficial to improving the long‐term stability. On the other hand, the formation of the chelating bonding effectively eliminates the deep‐level defects including PbI and Pb clusters on the Pb‐I and FA‐I terminations, respectively, as confirmed by theoretical simulation and experimental results. Consequently, the PCE is increased to 24.52%, open circuit voltage to 1.19 V, and fill factor to 81.53%; all three are among the highest for hybrid perovskite cells. The present strategy provides a straightforward means to enhance both the PCE and long‐term stability of PSCs. [ABSTRACT FROM AUTHOR]

The development of inorganic hole‐transporting materials (HTMs) is one of the most reliable ways to improve the stability of perovskite solar cells (PSCs). However, the un‐optimal buried interfacial contacts and the defects located at the inorganic HTMs/perovskite interface restricted the device's performance. Herein, a phase‐pure CuScO2 has been synthesized and further employed as mesoporous HTM in inverted PSCs. Surprisingly, a facile pretreatment of the hole‐transport layer by a formamidine salt compensates the I− vacancy of the buried perovskite film, thus regulating the interfacial band energy alignment between the HTM and perovskite. This ion compensation strategy can not only in situ repair the ion loss and improve the built‐in electric field, but also decrease the charge injection barrier and suppress the non‐radiative interfacial recombination. Benefiting from these merits, the resulting methylammonium‐free (MA), Cs/FA‐based PSCs displays a power conversion efficiency (PCE) of 22.42% along with excellent thermal and light stability. Moreover, the pre‐buried treatment strategy can be extended to MA‐containing CsFAMA triple‐cation perovskite film, and a champion inverted device delivers a PCE of 23.11%. This study offers a new avenue to the rational design of HTMs for highly efficient and stable PSCs. [ABSTRACT FROM AUTHOR]

All‐inorganic CsPbI3 perovskite presents preeminent chemical stability and a desirable band gap as the front absorber for perovskite/silicon tandem solar cells. Unfortunately, CsPbI3 perovskite solar cells (PSCs) still show low efficiency due to high density of defects in solution‐prepared CsPbI3 films. Herein, three kinds of hydrazide derivatives (benzoyl hydrazine (BH), formohydrazide (FH) and benzamide (BA)) are designed to reduce the defect density and stabilize the phase of CsPbI3. Calculation and characterization results corroborate that the carboxyl and hydrazine groups in BH form strong chemical bonds with Pb2+ ions, resulting in synergetic double coordination. In addition, the hydrazine group in the BH also forms a hydrogen bond with iodine to assist the coordination. Consequently, a high efficiency of 20.47 % is achieved, which is the highest PCE among all pure CsPbI3‐based PSCs reported to date. In addition, an unencapsulated device showed excellent stability in ambient air. [ABSTRACT FROM AUTHOR]

CsPbI2Br perovskite is known for its advantages over its organic‐inorganic hybrid counterpart including better thermal stability and appropriate bandgap for the front sub‐cell of tandem solar cell. However, its lower‐than‐satisfactory efficiency, problematic phase stability and sensitivity to moisture hinder its further advancement. Here, three kinds of glycine halides (Gly‐X: X = Cl, Br, and I) are strategically deigned to improve the performance of CsPbI2Br perovskite solar cells (PSCs). Systematic experimental and calculated results prove that a 2D/3D hybrid structure is formed, wherein the Gly‐X‐based 2D perovskite is mainly located at the CsPbI2Br grain boundaries, and the A‐sites of the 2D perovskite form strong bonds with the 3D perovskite to suppress ion migration by increasing its activation energy. As a result, a power conversion efficiency (PCE) of 17.26% was obtained with an open‐circuit voltage (VOC) of 1.33 V, which is among the best PCE values for the CsPbI2Br PSCs. In addition, the efficiency of encapsulated device decrease only by 14.1% after 340 h continuous illumination in ambient conditions, representing one of the most‐stable inorganic PSCs reported so far. This work provides important insights into designing passivating agents to address the issue of phase segregation for the development of highly stable perovskite optoelectronic devices. [ABSTRACT FROM AUTHOR]

The additive strategy is considered to be an effective scheme to purposefully passivate defect sites in perovskite materials. Herein, a small molecule trifluoroacetamide (TFAA) with C═O, −NH2, and F groups is incorporated into the perovskite precursor solution to alleviate the defect densities of the perovskite material from the source, so as to obtain high‐quality FA0.85MA0.15PbI3 perovskite absorber and its assembled photovoltaic devices. Thanks to the interactions of Lewis acid of C═O and undercoordinated Pb2+, N—H and I− via hydrogen bond, and F and FA+ fragments, the nonradiative recombination sites are effectively inhibited, simultaneously promoting the nucleation and grain growth of perovskite. The analysis results demonstrate that the introduction of TFAA additive greatly enhances the crystal quality of bulk perovskite absorber, ameliorates the surface morphology of perovskite film, and improves the extraction and transfer abilities of photogenerated carriers from perovskite absorber. The perovskite solar cells (PSCs) based on TFAA agent yield a champion power conversion efficiency of 24.16%, 8.3% better than that of the control device (22.31%). More importantly, the modified perovskite film has good harsh humidity stability and the unpackaged PSCs maintain outstanding photovoltaic performance in atmospheric environment, thermal, and light conditions. [ABSTRACT FROM AUTHOR]

Formamidinium methylammonium lead iodide (FAMAPbI3) perovskite has been intensively investigated as a potential photovoltaic material because it has higher phase stability than its pure FAPbI3 perovskite counterpart. However, its power conversion efficiency (PCE) is significantly inferior due to its high density of surface detects and mismatched energy level with electrodes. Herein, a bifunctional passivator, methyl haloacetate (methyl chloroacetate, (MClA), methyl bromoacetate (MBrA)), is designed to reduce defect density, to tune the energy levels and to improve interfacial charge extraction in the FAMAPbI3 perovskite cell by synergistic passivation of both CO groups and halogen anions. As predicted by modeling undercoordinated Pb2+, the MBrA shows a very strong interaction with Pb2+ by forming a dimer complex ([C6H10Br2O4Pb]2+), which effectively reduces the defect density of the perovskite and suppresses non‐radiative recombination. Meanwhile, the Br− in MBrA passivates iodine‐deficient defects. Consequently, the MBrA‐modified device presents an excellent PCE of 24.29%, an open‐circuit voltage (Voc) of 1.18 V (Voc loss ≈ 0.38 V), which is one of the highest PCEs among all FAMAPbI3‐based perovskite solar cells reported to date. Furthermore, the MBrA‐modified devices without any encapsulation exhibit remarkable long‐term stability with only 9% of PCE loss after exposure to ambient air for 1440 h. [ABSTRACT FROM AUTHOR]

It has been reported that an overlayer of lower dimensional perovskite can effectively improve the properties of 3D perovskite solar cells. Here, 4‐aminobutyric acid (C4I) and 6‐aminocaproic acid iodides (C6I) are introduced onto the surface of the perovskite layer, forming a low‐dimensional (LD) capping layer on the 3D perovskite films for high‐performance devices. It is found that C4I forms a 2D perovskite layer, while C6I forms a 1D perovskite layer on the 3D perovskite surface. By using the LD capping layers, the integrated perovskite films show passivated surface traps, reduced defect density, improved carrier lifetimes, and altered band alignment, leading to improved fill factor and open‐circuit voltage and, hence, significantly higher device efficiency. The devices with the C4I and C6I capping layers achieve solar cell efficiencies as high as 23.48% and 23.11%, respectively. In addition, bare devices with the C4I and C6I integration maintain 93.73% and 91.58%, respectively, of their initial efficiencies after exposure to the ambient atmosphere for 2000 h, demonstrating much better stability than the pristine 3D holding only 83.30% of its initial efficiency. It appears that this 2D capping is more suitable for enhancing 3D perovskite performance for general photoelectronic applications than the 1D capping. [ABSTRACT FROM AUTHOR]

Despite the swift development in perovskite solar cells (PSCs), suppressing the ion defects in the perovskite bulk and further extending the long‐lasting stability of the cells remain the concerned issues that are yet to be solved. Here, a symmetrical organic acceptor−donor−acceptor (A−D−A) molecule with the core architecture of indaceno[1,2‐b:5,6‐b']dithiophene (IDT) and bilateral arms of oxindole, named IDT‐OD, as a versatile defect passivation agent, is adopted to inactivate the nonradiative recombination sites in the perovskite absorber. The S element in the IDT unit and carbonyl group CO in the bilateral acceptor unit as the Lewis‐base contributes to the passivation sites that are the under‐coordinated Pb2+ cation defects and the N−H group in oxindole unit interacts with halide dangling bonds. The molecular structure with its symmetrical double arms assists the formation of a superior perovskite layer with enlarged grain size, smooth surface topography, hydrophobic property, and low density of defect state. Consequently, the corresponding PSCs with the proper IDT‐OD additive yield a remarkable increase in efficiency from 22.77% to 24.04%, along with excellent long‐term environmental and thermal stabilities. This study offers a propitious approach for ionic defect passivation engineering toward high‐performance PSCs. [ABSTRACT FROM AUTHOR]

Inorganic CsPbI2Br perovskite is promising for solar cell applications due to its excellent thermal stability and optoelectronic characteristics. Unfortunately, the current high‐efficiency CsPbI2Br perovskite solar cells (PSCs) are mostly fabricated in an inert atmosphere due to their instability to moisture. Herein, a low‐dimensional intermediate‐assisted growth (LDIAG) method is reported for the deposition of CsPbI2Br film in ambient atmosphere by introducing imidazole halide (IMX: IMI and IMBr) into the precursor solution to control both nucleation and growth kinetics. The IMX first combines with PbI2 in the precursor film to form a 2D intermediate which then gradually releases PbI2 to slowly form high‐quality CsPbI2Br film during annealing. It is found that the LDIAG method produces a uniform, highly crystalline, pinhole‐free, and stable CsPbI2Br film with low defect density. Consequently, the solar cell efficiency is increased to as high as 17.26%, one of the highest for this type of device. Furthermore, the bare device without any encapsulation shows excellent long‐term stability with ≈86% of its initial efficiency retained after being exposed to the ambient environment for 1000 h. This work provides a perspective to tune the intermediate phases and crystallization pathway for high‐performance inorganic PSCs formed under ambient conditions. [ABSTRACT FROM AUTHOR]

Ligand‐solvent engineering has been widely applied to improve the quality of perovskite films by forming intermediate films. However, there is an inconsistent understanding in the studies on the composition and mechanism of intermediate films formed by different ligand solvents, and the influence on perovskite film morphology is still elusive. Herein, the pure intermediate films (composed of pure crystal nucleus and amorphous precursor) are fabricated by the addition of ligand solvents with different coordination abilities. Notably, a single heterogeneous nucleation process is induced by the pure intermediate film, resulting in the formation of vertically arranged internal perovskite crystals with few horizontal boundaries, that improve charge transfer and device performance. Furthermore, the small and uniform crystals obtained by adding a ligand solvent with weak coordination ability result in smooth films and a smaller device current (Jsc = 22.74 mA cm−2, PCE = 19.58%). In contrast, the large and uneven crystals obtained by strong coordination ability lead to rough films and a larger device current (Jsc = 23.24 mA cm−2, PCE = 20.72%). This study is devoted to providing a significance reference for the fabrication of perovskite films with vertically arranged internal grains and superior surface textures. [ABSTRACT FROM AUTHOR]

The fabrication of large area perovskite solar modules (PSMs) is attracting increasing attention. Traditionally, thin film solar modules are prepared by laser‐engraving several isolated lines to create a series of subcells. This process inevitably leads to an increase in series resistance when combining the subcells. Herein, a facile structure combining series and parallel cell connections is designed and developed for constructing PSMs. A champion power conversion efficiency (PCE) of 18.82% is achieved for perovskite composite modules with a designated area of 21.06 cm2. Furthermore, the PSMs can continue to operate even when parts of the device are shaded or broken. Because of the repeated structural arrangement, these modules may be suitable for fabrication on a broader scale for commercial applications. [ABSTRACT FROM AUTHOR]

N2,N2,N8,N8‐tetrakis(4‐(methylthio)phenyl)dibenzo[b,d]thiophene‐2,8‐diamine (DBTMT) is synthesized from three commercial monomers for application as a promising dopant‐free hole‐transport material (HTM) in perovskite solar cells (pero‐SCs). The intrinsic properties (optical properties and electronic energy levels) of DBTMT are investigated, proving that DBTMT is a suitable HTM for the planar p–i–n pero‐SCs. The champion power conversion efficiency (PCE) of the optimized pero‐SCs (with structure as ITO/pristine DBTMT/MAPbI3/C60/BCP/Ag) reaches 21.12% with a fill factor (FF) of 83.25%, which is among the highest PCEs and FFs reported for planar p–i–n pero‐SCs based on dopant‐free HTMs. The Fourier‐transform infrared spectroscopy, X‐ray diffraction, and X‐ray photoelectron spectroscopy spectra of MAPbI3 and DBTMT–MAPbI3 films demonstrate that there is an interaction between DBTMT and MAPbI3 at the interface through the sulfur atoms in DBTMT to passivate the defects, which is corresponding to the higher FF and PCE of the corresponding device. [ABSTRACT FROM AUTHOR]

As the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is increased to as high over 25%, it becomes pre‐eminent to study a scalable process with wide processing window to fabricate large‐area uniform perovskite films with good light‐trapping performance. A stable and uniform intermediate‐state complex film is obtained by using tetramethylene sulfoxide (TMSO), which extends the annealing window to as long as 20 min, promotes the formation of a high‐quality perovskite film with larger grains (over 400 nm) and spontaneously forms the surface texture to result in an improved fill factor and open‐circuit voltage (Voc). Moreover, the superior surface texture significantly increases the long‐wavelength response, leading to an improved short‐circuit current density (Jsc). As a result, the maximum PCE of 21.14% is achieved based on a simple planar cell structure without any interface passivation. Moreover, a large area module with active area of 6.75 cm2 is assembled using the optimized TMSO process, showing efficiency as high as 16.57%. The study paves the way to the rational design of highly efficient PSCs for potential scaled‐up production. [ABSTRACT FROM AUTHOR]

Perovskite solar cells are sensitive to subtle changes in atmospheric conditions, resulting in problems such as the collapse of the perovskite structure and sharp drops in efficiency. Internal defects are also a big obstacle for high‐quality polycrystalline perovskites. At present, it is difficult to control the density of the trapping sites. By using the bidentate chelating agent thenoyltrifluoroacetone (ttfa), the crystallization kinetics, grain sizes, and crystal defect of Cs‐, methylammonium‐, and formamidinium‐based perovskite materials can be to effectively controlled through a nucleation and growth process for the preparation of perovskite crystals. Crystalline‐state tuning during the crystallization process to obtain better quality perovskite thin films can be achieved with no additional operation, which is suitable for the needs of modern industrial production and management. The chelating agent can effectively passivate the defects in perovskite films, leading to a low defect density and a long charge carrier lifetime. As a result, the ttfa‐passivated perovskite solar cell demonstrated a high power conversion efficiency of 19.70 % with superior stability retention of 64 % of the initial power conversion efficiency after two weeks unencapsulated storage in an adverse atmosphere with approximately 50 % relative humidity. [ABSTRACT FROM AUTHOR]

Exploration of low‐temperature solution‐processing methodologies for fabricating planar perovskite solar cells (PSCs) is important for industrial mass production and helps simplify the manufacture and design of flexible perovskite solar cells. However, the interface between electron‐transport layers (ETLs) and perovskite layers is crucial for the development of highly efficient flexible PSCs. We report a drastically improved solar cell efficiency through surface optimization of TiO2 ETLs by using a simple and inexpensive ionic compound that shows high optical transparency and superior electron mobility. Solution‐derived TiO2 nanocrystalline films are employed at low temperatures as ETLs through solution processing. The modification of TiO2 with NH4Cl can increase the interactions between the surface and organic–inorganic hybrid perovskites; Cl anions lead to a stronger interfacial coupling between TiO2 and perovskite. Ammonium cations tend to combine with perovskite. Due to this strong combined effect of the ionic compound, the efficiency of PSC from low‐temperature solution processing reaches 18.71 % on rigid glass/indium tin oxide (ITO) for an improvement of 12.6 % over a control device using bare TiO2. Furthermore, the power conversion efficiency (PCE) can reach an efficiency of 17.69 % for the ITO/PEN substrates. This work contributes to the evolution of flexible PSCs with simple fabrication and high device performance. Scrubbing the surface for performance: Performance loss that arises from imperfect interfaces and charge recombination between electron‐transport layers (ETLs) and perovskite cannot be ignored. NH4Cl has been used to modify TiO2 in an effort to passivate surface defects and increase the interactions between the surface and the organic–inorganic hybrid lead halide perovskite compounds. NH4Cl can passivate both sides of TiO2/perovskite simultaneously benefitting both ETLs and perovskites. [ABSTRACT FROM AUTHOR]

The electron transport layer (ETL) plays a crucial role in the rapidly developed perovskite solar cells (PSCs). SnO2 has become one of the most promising alternatives to the TiO2 ETL due to its superior characteristics, such as the wider bandgap and hysteresis-free. However, at this stage, a lot of preparation methods of SnO2 ETL exist in high temperature and long time, those undoubtedly increase the cost and time of preparation. Herein, we report a low-temperature solution-processed SnO2 ETL without high annealing temperature, and a special bromine salt is used to modify SnO2, which leads to a higher transmittance and improved carrier transport ability. Due to the excellent optical and electrical properties, the photoelectric conversion efficiency of the prepared PSC reaches up to 18.8%. Moreover, it can be fabricated using facile solution processing at low temperature, making it particularly attractive for flexible development and low-cost commercialization.ᅟ [ABSTRACT FROM AUTHOR]

0.14 at% Mn-doped 0.95(Na 1/2Bi 1/2)TiO 3-0.05BaTiO 3 (0.95NBT-0.05BT) lead-free single crystals were grown by a top-seeded solution growth method (TSSG). X-ray powder diffraction measurement showed that the as-grown single crystals exhibit rhombohedral perovskite structure with apparent distortion. With the increase of temperature, successive structural phase transitions occur in the Mn-doped 0.95NBT-0.05BT single crystals. After poling, apparent dielectric anomaly is induced accompanied by the increase of the character of diffuse phase transition and the decrease of the value of dielectric constant. The Mn-doped 0.95NBT-0.05BT single crystals exhibit complex domain structure, in which micro and macro domains coexist with statistically 4 mm symmetry. The Mn-doped 0.95NBT-0.05BT lead-free single crystals exhibit excellent piezoelectric and pyroelectric properties, which will lead to promising advance in piezoelectric and pyroelectric applications. The infrared-absorption band occurred around 630.6 cm −1 can be assigned to the “stretching” normal vibration of [Na 1/2Bi 1/2]/Ti-O group. The three diffused Raman bands centered around 300, 560 and 800 cm −1 can be attributed to F2g [TiO 6] bending vibration, A1g [TiO 6] stretching vibration and “soft mode” mixed by bending and stretching vibrations. [ABSTRACT FROM AUTHOR]

Multijunction/tandem solar cells have naturally attracted great attention because they are not subject to the Shockley–Queisser limit. Perovskite solar cells are ideal candidates for the top cell in multijunction/tandem devices due to the high power conversion efficiency (PCE) and relatively low voltage loss. Herein, sandwiched gold nanomesh between MoO3 layers is designed as a transparent electrode. The large surface tension of MoO3 effectively improves wettability for gold, resulting in Frank–van der Merwe growth to produce an ultrathin gold nanomesh layer, which guarantees not only excellent conductivity but also great optical transparency, which is particularly important for a multijunction/tandem solar cell. The top MoO3 layer reduces the reflection at the gold layer to further increase light transmission. As a result, the semitransparent perovskite cell shows an 18.3% efficiency, the highest reported for this type of device. When the semitransparent perovskite device is mechanically stacked with a heterojunction silicon solar cell of 23.3% PCE, it yields a combined efficiency of 27.0%, higher than those of both the sub‐cells. This breakthrough in elevating the efficiency of semitransparent and multijunction/tandem devices can help to break the Shockley–Queisser limit. [ABSTRACT FROM AUTHOR]

For commercial applications, it is a challenge to find suitable and low‐cost hole‐transporting material (HTM) in perovskite solar cells (PSCs), where high efficiency spiro‐OMeTAD and PTAA are expensive. A HTM based on 9,9‐dihexyl‐9H‐fluorene and N,N‐di‐p‐methylthiophenylamine (denoted as FMT) is designed and synthesized. High‐yield FMT with a linear structure is synthesized in two steps. The dopant‐free FMT‐based planar p‐i‐n perovskite solar cells (pp‐PSCs) exhibit a high power conversion efficiency (PCE) of 19.06%, which is among the highest PCEs reported for the pp‐PSCs based on organic HTM. For comparison, a PEDOT:PSS HTM‐based pp‐PSC is fabricated under the same conditions, and its PCE is found to be 13.9%. [ABSTRACT FROM AUTHOR]

Recently, inorganic CsPbI2Br perovskite is attracting ever‐increasing attention for its outstanding optoelectronic properties and ambient phase stability. Here, an efficient CsPbI2Br perovskite solar cell (PSC) is developed by: 1) using a dimension‐grading heterojunction based on a quantum dots (QDs)/bulk film structure, and 2) post‐treatment of the CsPbI2Br QDs/film with organic iodine salt to form an ultrathin iodine‐ion–enriched perovskite layer on the top of the perovskite film. It is found that the above procedures generate proper band edge bending for improved carrier collection, resulting in effectively decreased recombination loss and improved hole extraction efficiency. Meanwhile, the organic capping layer from the iodine salt also surrounds the QDs and tunes the surface chemistry for further improved charge transport at the interface. As a result, the champion device achieves long‐term stabilized power conversion efficiency beyond 14%. Here, an AI treatment is developed that provides a general method for optimizing the interfacial properties of inorganic perovskite solar cells, which leads to proper band edge bending, decreased surface defects, and a high‐quality quantum dots–modified layer. These changes prove effective at decreasing recombination loss and improving hole extraction efficiency. As a result, the FAI‐treated champion device achieves long‐term stabilized power conversion efficiencies above 14%. [ABSTRACT FROM AUTHOR]

We thoroughly investigated the carrier-phonon relaxation process in 2D halide perovskites with the general formula of (BA)2(MA)n-1PbnI3n+1, where n = 2, 3, and 4, by femtosecond transient absorption spectroscopy. A significant enhancement of the hot phonon bottleneck effect is observed in the natural multiple quantum well with n = 2 and 3. Specifically, the sample with n = 3 shows a 1000 ps hot carrier relaxation time to reach room temperature, which is 10 times longer compared with its three-dimensional counterpart. We believe that both the organic cation and quantum confinement effect are responsible for this phenomenon. The acoustic phonon cannot propagate due to the decrease in group velocity caused by the confinement effect in such a quantum well structure. In addition, the confined acoustic phonons can up-convert to optical phonons due to the presence of a “hybrid phonon” induced by the organic cation. This result suggests a promising way to obtain long-live hot carrier materials. [ABSTRACT FROM AUTHOR]

Here, antimonene nanosheets (ANs) were prepared by electrochemical lithiation intercalation and ultrasonication process for the first time, which were introduced onto the top of perovskite precursor film as heterogeneous nucleation sites. ANs can adsorb FAI/MAI to epitaxially grow perovskite film along their (012) planes. The perovskite solar cells with ANs assisted growth show high stability and an impressive efficiency of 24.54%. [Display omitted] There are many grain boundaries and defects in polycrystalline perovskite films, resulting in sacrificed efficiency and instability for perovskite solar cells (PSCs). By regulating the growth of perovskite grains along the vertical direction through epitaxial growth, one may expect fewer grain-boundaries, effective charge transport, improved crystalline quality, and reduced defect density. However, there is still no suitable epitaxial growth substrate for perovskite. Here, we developed an electrochemical lithiation intercalation and ultrasonication method to prepare high-quality antimonene nanosheets (ANs). It is found that the perovskite film grows preferentially along the (012) planes of the ANs that have perfect lattice match with the (001) planes of the perovskite, leading to a high-quality perovskite film with a preferential orientation along the [001] direction and greatly enlarged grain size. Consequently, the oriented perovskite-based PSC achieves a remarkable PCE of 24.54% and shows an enhanced stability under ambient conditions, thermal annealing or light illumination. This work opens an effective avenue to effectively control the oriented growth of perovskite film for high-performance perovskite optoelectrical devices. [ABSTRACT FROM AUTHOR]

For the rocket development of organic-inorganic hybrid perovskite solar cells (OIH–PSCs), the research of low-cost, dopant-free hole-transporting materials (HTMs) with high performance and stability is still an urgent problem. In this work, we synthesize organic small molecule HTM with sulfone-containing benzodithiophene (BDTOxide) as the central unit, termed BDTOxide-MTP. The synthetic cost of DBTOxide-MTP in the lab is 238 CNY/g, which is just one-fifth of the cost of the PTAA (1200 CNY/g). BDTOxide-MTP exhibits the deep highest occupied molecular orbital energy level, high hole transport mobility, and excellent passivation effect. BDTOxide-MTP is introduced into inverted OIH-PSCs as a dopant-free hole transport layer, the champion efficiency of MAPbI 3-x Cl x -based devices reaches 18.72 % with an excellent V OC of 1.13 V, while the efficiency of the control device based on PTAA is about 18.49 %. The device based on BDTOxide-MTP exhibits comparable stability to the one based on PTAA, which can maintain over 90 % of the original efficiency after 46 days in a nitrogen environment. [Display omitted] • Sulfone-containing dopant-free hole-transporting material has been synthesized. • The synthetic cost of it in the lab is 238 CNY/g. • It exhibits a deep HOMO and passivating effect. • The highest efficiency of it reaches 18.72 % with an excellent V OC of 1.13 V. [ABSTRACT FROM AUTHOR]

Abstract: Pure rhombohedral perovskite 0.8Pb(Mg1/3Nb2/3)O3–0.2PbTiO3 (0.8PMN–0.2PT) ceramics were prepared by the reaction-sintering method. The synthesized 0.8PMN–0.2PT ceramics exhibit very high relative density. At room temperature, dielectric constant and loss tangent of the 0.8PMN–0.2PT ceramics are 2360 and 0.0434 at 100Hz, respectively, and pyroelectric coefficient is 1337μC/Km2″. The calculated detectivity and voltage responsivity figures of merit F d and F v are 16.81μPa−1/2 and 0.0244m2/C, respectively, which increase slightly over the frequency range 100–2000Hz. Such investigation reveals that high-performance pyroelectric materials can be obtained in low production cost, which provides promising candidates for infrared detectors and other pyroelectric applications. [Copyright &y& Elsevier]

Titanium oxide (TiO 2) and tin oxide (SnO 2) are the most commonly used electron transport materials for high-efficiency n-i-p perovskite solar cells (PSCs); however, several limiting properties of TiO 2 and SnO 2 adversely affect device performance. This study describes a facile method to synthesize SnO 2 :TiO 2 hybrid nanocrystals (NCs) to construct electron transport layers (ETLs) with the advantageous properties of both SnO 2 and TiO 2 for n-i-p PSCs. The optimized SnO 2 :TiO 2 ETL exhibited better surface morphology, well-matched band alignment, higher direct current conductivity, and enhanced electron extraction and transport compared to pristine TiO 2 and SnO 2 ETLs. Moreover, perovskite films deposited on SnO 2 :TiO 2 ETLs exhibited a higher crystallinity and lower trap-state density than those on TiO 2 or SnO 2 ETLs. Therefore, SnO 2 :TiO 2 -based devices showed high performance (with a power conversion efficiency of 23.19%) and stability (with more than 83% retention of the initial efficiency after 800 h of continuous illumination). This study provides a new method for developing low-cost and efficient ETLs for n-i-p PSCs and confirms that constructing SnO 2 :TiO 2 hybrid ETL is an effective method to fabricate high-efficiency and stable planar perovskite solar cells. [Display omitted] • A facile method was developed to synthesize SnO 2 :TiO 2 hybrid nanocrystals. • The SnO 2 :TiO 2 hybrid ETL exhibited the advantageous properties of both TiO 2 and SnO 2. • Perovskite films deposited on SnO 2 :TiO 2 ETLs exhibited a high crystallinity and low trap-state density. • SnO 2 :TiO 2 -based devices had a PCE of 23.19% with >83% retention after 800 h of continuous illumination. [ABSTRACT FROM AUTHOR]

Solution-processed solar cells are promising as low-cost alternatives to the first-generation solar cells. Combining two solution-processed devices in a tandem structure can potentially achieve a high efficiency while maintaining a relatively low fabrication cost. Here we present a tandem combining solution-processed perovskite and CZTSSe solar cells in a reflective configuration. The perovskite cell with a large bandgap acts as a spectral filter reflecting the sub-bandgap photons to a low bandgap CZTSSe cell. A total efficiency of 16.1% has been obtained in a four-terminal measurement, higher than each of the sub-cells. These results show the potential of solution-processed tandem solar cell with perovskite and kesterite in achieving a high efficiency with a low fabrication cost. [ABSTRACT FROM AUTHOR]

Organohalogen perovskites are attracting considerable attention for use in solar cells. However, the stability of these devices will determine whether they can be made commercially viable. Device encapsulation or the use of a hydrophobic hole-transporting material can prevent the permeation of water into the perovskite layer and enhance the humidity stability of the cells under dark conditions. With regard to the light stability of solar cells, recent studies have yielded contradictory results. This work investigated the degradation mechanism of perovskite solar cells under illumination. Further, a simple method was proposed for improving their illumination stability. Amino acids were inserted between the compact TiO layer and the perovskite layer to effectively prevent the decomposition of the perovskite layer owing to the superoxide anions and hydroxyl radicals generated under illumination from the HO and O adsorbed onto the TiO layer. [ABSTRACT FROM AUTHOR]

All‐inorganic CsPbI3 perovskite presents preeminent chemical stability and a desirable band gap as the front absorber for perovskite/silicon tandem solar cells. Unfortunately, CsPbI3 perovskite solar cells (PSCs) still show low efficiency due to high density of defects in solution‐prepared CsPbI3 films. Herein, three kinds of hydrazide derivatives (benzoyl hydrazine (BH), formohydrazide (FH) and benzamide (BA)) are designed to reduce the defect density and stabilize the phase of CsPbI3. Calculation and characterization results corroborate that the carboxyl and hydrazine groups in BH form strong chemical bonds with Pb2+ ions, resulting in synergetic double coordination. In addition, the hydrazine group in the BH also forms a hydrogen bond with iodine to assist the coordination. Consequently, a high efficiency of 20.47 % is achieved, which is the highest PCE among all pure CsPbI3‐based PSCs reported to date. In addition, an unencapsulated device showed excellent stability in ambient air. [ABSTRACT FROM AUTHOR]

CsPbI 2 Br perovskites are promising candidates for photovoltaic applications owing to the trade-off between the optoelectronic properties and phase stability of cesium-based inorganic perovskites. However, the major shortcomings of CsPbI 2 Br perovskite solar cells (PSCs), namely energy loss and poor moisture resistance, still need to be addressed. In this work, reversible degradation-assisted decoration with Cs 4 PbBr 6 nanocrystals (NCs) is used to passivate the perovskite/hole transporting material (HTM) interface. Moisture-induced Cs 4 PbBr 6 decomposition products (CsPbBr 3 and CsBr) and CsPbI 2− x Br 1+ x (x > 0), generated as a result of halide anion exchange between CsPbI 2 Br and Cs 4 PbBr 6 or its decomposition products, are found to improve the quality of the CsPbI 2 Br film and suppress the trap state density. In addition, the decoration achieves desirable energy-level alignments at the CsPbI 2 Br/HTM interface and raises the Fermi level of the CsPbI 2 Br film, thereby strengthening the built-in electric field between the perovskite and HTM. As a result, the optimized CsPbI 2 Br PSC has a champion efficiency of 15.52% with an open-circuit voltage of 1.30 V (mean value: 1.29 V). The unencapsulated CsPbI 2 Br film and device both exhibit high air stability (∼40% humidity), and the latter retains 90% of its initial efficiency after a 500 h aging test. [Display omitted] • Decoration with Cs 4 PbBr 6 nanocrystals and subsequent reversible degradation. • The decoration improves crystal quality and suppresses trap state density. • Strengthening of the built-in electric field are also achieved by the decoration. • PSC V OC and moisture stability are simultaneously improved. [ABSTRACT FROM AUTHOR]

• A small molecule hole transport materials (HTM, DFBT-PMTP) has been designed. • DFBT-PMTP canbe applied without doping and annealing in perovskites solar cells. • The efficiency of the corresponding p-i-n device reaches to as high as 21.23%. Hole transport materials (HTMs) play an important role in perovskites solar cells (Pero-SCs) which can greatly affect the stability and power conversion efficiency (PCE). While most of the efficient HTMs need doping (which results in poor stability) or the treatment of thermal annealing (which increases the complexity of the device fabrication process). In this work, we synthesized a small molecule HTM DFBT-PMTP based on 3,3′-difluoro-2,2′-bithiophene and applied it as HTM without the need for doping and thermal annealing in p-i-n Pero-SCs with the structure of ITO/HTM/MAPbI 3−x Cl x /C 60 /BCP/Ag. The PCE of the corresponding devices achieves a high value of 21.23% (19.8% for the PTAA-based reference ones), with an open-circuit voltage of 1.17 V and a high fill factor of 82.28%, which is to date among the highest values for the p-i-n MAPbI 3−x Cl x –based Pero-SCs. Interestingly, the PCE of the devices declined to 18.65 and 15.5%, while the annealing temperature of DFBT-PMTP increased to 100 and 150 °C, respectively. And the reasons for this abnormal phenomenon have been investigated including the intrisinc properties, the energy levels of MAPbI 3−x Cl x on top and the decices performance of the DFBT-PMTP films without annealing and annealed at 100 and 150 °C, respectively. The results revealed that the precise molecular structure design for the HTMs can make huge changes in the corresponding photovoltaic properties and fabrication process due to the effects on the top perovskites. [ABSTRACT FROM AUTHOR]

• Perovskite with an inhomogeneous composition was fabricated. • Inhomogeneous distribution of Cl element creates Cl-rich modification layer. • The modification layer improves the photoelectrical performance. A perovskite compositional difference was engineered at the perovskite/electron transport layer (ETL) interface. The devices with inhomogeneous perovskite composition achieve the best power conversion efficiency of 16.1% under the optimal conditions, compared with 12.5% for the control, and the device stability is also improved. Further characterizations indicate that the performance enhancement is due to the larger perovskite grain size with less pinholes, the improved charge extraction at the perovskite/ETL interface, and the reduced charge recombination. This modification effect is induced by constructing an additional Cl-rich layer on bottom of the primary CH 3 NH 3 PbI 3 film. [ABSTRACT FROM AUTHOR]

To implement the commercialization of perovskite solar cells (pero-SCs) in the future, employing high-efficiency and low-cost hole-transporting materials (HTMs) is one of crucial factors. Herein, through investigating the electronic structure and geometry of the molecular structure with density functional theory calculation, a dibenzo[ b,d ]furan-centred molecular hole-transporting material (termed DBFMT) is synthesized from commercial monomers with a relatively low cost of approximately US$35 per gram in laboratory. This dopant-free HTM is applied in the planar p-i-n pero-SCs with a structure of ITO/DBFMT/perovskite (MAPbI 3)/C 60 /BCP/Ag. Based on the different concentration of DBFMT, the corresponding top perovskite grain sizes are different. After optimization, the power conversion efficiency (PCE) reaches as high as 20.51%, with a short-circuit current density of 23.70 mA cm−2, an open circuit voltage of 1.07 V, and a fill factor of 80.48%. As far as we know, the PCE of 20.51% is among the highest efficiency for the p-i-n pero-SCs based on the dopant-free HTMs. Image 1 • A dibenzo[ b,d ]furan-centred linear hole-transporting material (L-HTM) was synthesized. • This dopant-free L-HTM was applied in planar p-i-n perovskite solar cells (pero-SC). • The highest efficiency of 20.51% achieved among the dopant-free L-HTM-based pero-SC. [ABSTRACT FROM AUTHOR]