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As electron transport layers (ETLs) in perovskite solar cells (PSCs), tin oxide (SnO2) possess high carrier mobilities with appropriate energy band alignment and high optical transmittance. Herein, SnO2 ETLs were fabricated by intermediate‐controlled chemical bath deposition (IC‐CBD) at ultralow temperature, where the chelating agent effectively altered the nucleation and growth process. Compared with conventional CBD, SnO2 ETLs fabricated by IC‐CBD had lower defects, smooth surface, good crystallinity, and remarkable interfacial contact with perovskite, resulting in good quality of perovskite, high photovoltaic performance (23.17 %), and enhanced stability of devices. [ABSTRACT FROM AUTHOR]

The photoelectric properties of nontoxic Sn‐based perovskite make it a promising alternative to toxic Pb‐based perovskite. It has superior photovoltaic performance in comparison to other Pb‐free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi‐interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long‐term stability. [ABSTRACT FROM AUTHOR]

The photoelectric properties of nontoxic Sn‐based perovskite make it a promising alternative to toxic Pb‐based perovskite. It has superior photovoltaic performance in comparison to other Pb‐free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi‐interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long‐term stability. [ABSTRACT FROM AUTHOR]

The performance of inverted perovskite solar cells (PSCs) is highly dependent on the surface properties of the hole‐transport layers (HTLs). Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most widely used HTLs due to its excellent properties. However, some drawbacks severely limit its application in PSCs. Herein, multifunctional bulk organic ammonium salts (BOASs) are deposited onto PEDOT:PSS films and used for interfacial modifications. The BOASs‐modified PEDOT:PSS has better energy‐level alignment with perovskite (PVK) than PEDOT:PSS, resulting in the suppressed voltage loss of PSCs. Depositing BOASs on top of the PSS isolates moisture to inhibit the ionization of sulfonic acid groups, which is beneficial to reduce the acidity and corrosiveness of PEDOT:PSS. In addition, the interfacial modification of BOASs can effectively enlarge the surface energy of PEDOT:PSS films and improve the morphology of the PVK layer. Therefore, the open‐circuit voltage and fill factor of the PSCs based on BOASs‐modified PEDOT:PSS are simultaneously increased to a maximum of 1.03 V and 73%, respectively, resulting in a champion device efficiency of 18.37%. The unencapsulated PSCs based on BOASs‐modified PEDOT:PSS remain more than 80% power conversion efficiency loss after 700 h of exposure to air. [ABSTRACT FROM AUTHOR]

Halide perovskites are intensively studied for applications in optoelectronic devices because of their outstanding properties and relatively low cost. However, the common precursor solutions for perovskite fabrication are rather unstable in the presence of moisture and oxygen, limiting the large‐scale low‐cost production of perovskite. Herein, water is used counterintuitively to formulate an ambient stable perovskite precursor, which is peculiar in that it is solid at room temperature but becomes a liquid at 75 °C. The non‐fluidity of the precursor stemmed from the water‐assisted intermediate fiber assembly, conferring high damp air stability. Yet the heat‐liquefiability made the precursor highly processible for perovskite growth, and when guided by polyvinyl pyrrolidone coordination with Pb2+, the perovskite can preferentially grow along the [200] direction, significantly improving the film quality. To demonstrate the utility of the precursor, it has been used to fabricate self‐driven halide perovskite photodetectors, which exhibited a low noise current of 2.0 × 10−14 A Hz−1/2, a high specific detectivity up to 1.4 × 1013 Jones, and high stability of 20 days of operation with only < 5% external quantum efficiency decay. This type of solid‐liquid convertible precursor opens up new opportunities for wider applications of perovskites. [ABSTRACT FROM AUTHOR]

The elimination of electron transport layers (ETLs) to fabricate ETL-free perovskite solar cells (PSCs) could save manufacturing costs and time. However, compared with PSCs based on the traditional architecture, ETL-free PSCs suffered low efficiency due to the device shunting and large energy barriers for carriers. Herein, a bifunctional interfacial modification material, 3-aminopropyl trimethoxy silane (APS), is selected and in situ grown on a transparent conducting oxide (TCO). On the one hand, the increased hydrophobicity of APS modified indium tin oxide (ITO) could improve the crystal growth of perovskites, resulting in larger grain sizes and reduced surface defects. On the other hand, the APS modification could improve the energy level alignment of ITO and the perovskite, leading to enhanced electron extraction and hole blocking. The PCE of the ETL-free PSCs based on APS modified ITO reached 19.09%, which was over 60% higher than that of ETL-free PSCs based on ITO. [ABSTRACT FROM AUTHOR]

Controlling the crystallographic orientations of 2D perovskite is regarded as an effective way to improve the efficiency of PSCs based on 2D perovskite. In this paper, five different assistant solvents were selected to unveil the effect of solvents on crystallization and morphology of 2D perovskite in a solvent-assisted method. Results demonstrated that the effect of Lewis basicity on the crystallization process was the most important factor for preparing 2D perovskite. The stability of the intermediate, reacted between the solvent and the Pb2+, determined the quality of 2D film. The stronger the Lewis basicity was, the more obvious the accurate control effect on the top-down crystallization process of 2D perovskite would be. This could enhance the crystallographic orientation of 2D perovskite. The effect of Lewis basicity played a more important role than other properties of the solvent, such as boiling point and polarity. [ABSTRACT FROM AUTHOR]

Due to the low cost and strong hydrophobicity of carbon electrodes, carbon-based perovskite solar cells (C-PSCs) have drawn much attention. Copper(I) thiocyanate (CuSCN) is a favorable hole transport layer in perovskite solar cells (PSCs) because of its high chemical stability, high conductivity, and high hole mobility, but pinholes often appear during CuSCN film fabrication. In this work, organic ammonium salt, phenethylammonium iodide (PEAI), has been applied to modify the CuSCN film. The results indicated that PEAI not only eliminated the pinholes, but also passivated the perovskite film and enhanced the interfacial connection. Therefore, the power conversion efficiency (PCE) of C-PSCs increased by about 11%. The stability test showed that the C-PSCs, without any encapsulation, could maintain 70% of the initial efficiency after storage for 800 h in ambient air with 60%–70% relative humidity at room temperature. [ABSTRACT FROM AUTHOR]

Though perovskite solar cells (PSCs) or modules (PSMs) are being developed at an unprecedented speed, several obstacles remain to their commercialization. One of the difficult problems is the expensive and unstable Au and Ag counter electrode. Therefore, highly effective, stable, and low‐cost counter electrode materials should be explored. Among various counter electrode materials, carbon is one of the most promising substitutes for their rich sources, low cost, outstanding electrochemical performance, and diversified surface functions. This review summarizes recent achievements of carbon counter electrode materials, which included commercial carbon paste, carbon black, graphite, graphene, carbon nanotubes and their synthetic approaches, modifications, and structure‐function relationships. Moreover, large‐scale carbon counter electrode in PSCs or PSMs are specifically discussed. Hopefully, this recapitulative analysis will draw the attention of relevant researchers to re‐understand the importance of counter electrode and clarify what should be noticed to develop qualified counter electrode materials for PSCs or PSMs. [ABSTRACT FROM AUTHOR]

Power conversion efficiencies (PCEs) of up to 25.5 % have been reported for perovskite solar cells (PSCs). Thus, they have shown great potential for commercial applications. Therefore, simplifying technological process and reducing production costs have been a widespread concern among scientific and industrial communities. In this study, PSCs are prepared with the simplest device architecture (FTO/MAPbI3/carbon). A high‐quality perovskite film with few interface defects and good carrier transport is obtained by tuning the p‐n properties, matching energy levels, and enhancing carrier collection and transport. A PCE of 12.01 % is achieved, which is the best reported to date for this device structure. The device also shows excellent long‐term stability, owing to the elimination of charge transport layers and the usage of hydrophobic materials. This study provides a new approach to reduce production costs and simplify production of PSCs. [ABSTRACT FROM AUTHOR]

Two dimensional (2D) perovskite materials, are more stable than 3D perovskite materials, which could solve the stability issue of perovskite solar cells (PSCs). However, the photovoltaic conversion efficiency (PCE) of PSCs based on 2D perovskite materials was low, due to the high dielectric and quantum confinement of 2D perovskite. In this work, we propose a solvent-assisted method to prepare 2D perovskite films, where the solvent was distributed in a gradient. Therefore, the top-down crystallization process of 2D perovskite can be accurately controlled. The PCE of PSCs fabricated by the solvent-assisted method was enhanced by 48%, compared with the control device. For the packaged devices, the stability test demonstrated that 94% of the initial PCE was still maintained after 1500 hours of storage (25 °C, RH 40%). After carefully analyzing the photophysical process of the carriers in the PSCs based on 2D perovskite, the enhanced carrier transfer mechanism of the solvent-assisted method has been proposed. [ABSTRACT FROM AUTHOR]

Carbon‐based hole transport material (HTM)‐free CsPbI2Br perovskite solar cells (C‐PSCs) have garnered considerable attention due to their super thermal stability. The energy‐level mismatch between the CsPbI2Br perovskite and carbon electrodes, however, results in major energy loss and reduced power conversion efficiency (PCE) of C‐PSCs. Herein, 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIMBF4) is used to manage the energy level, reduce defect densities, and improve the interface quality between CsPbI2Br and carbon electrodes. Preliminary results demonstrate that the BMIMBF4 modifier can passivate the surface defects of the perovskite film and reduce the energy‐level mismatch between the CsPbI2Br layer and the carbon electrode. A PCE of 14.03% is achieved by introducing BMIMBF4 which is improved by 23% compared with the control device (11.37%). Moreover, stability—whether in the case of C‐PSCs or CsPbI2Br films—is also improved. [ABSTRACT FROM AUTHOR]

In the past decade, organic–inorganic hybrid perovskite solar cells (PSCs) have begun to be increasingly studied worldwide owing to the superior properties of perovskite material. However, some issues have delayed their commercialization, such as their long‐term stability, cost reduction, scale‐up ability, and efficiency. The introduction of sulfur to PSCs can relieve the above issues because sulfur can passivate interfacial trap states, suppress charge recombination, and inhibit ion migration, thereby enhancing the stability of PSCs. Furthermore, PbS bonds provide new channels for carrier extraction. Herein, the sulfur‐based compounds utilized in PSCs are summarized and classified according to their functions in the different layers of PSCs. The results indicate that these sulfur‐based compounds have efficiently promoted the commercialization of PSCs. It is hoped that this review can help others understand the intrinsic phenomena of sulfur‐based PSCs and motivate additional investigations. [ABSTRACT FROM AUTHOR]

Herein, it is reported that the stability of a halogenated perovskite (PVK) solar cell consisting of an fluorine‐doped tin oxide (FTO) substrate/TiO2/CH3NH3PbI3/N2,N2,N2′,N2′,N7,N7,N7′,N7′‐octakis(4‐methoxyphenyl)‐9,9′‐spirobi[9H‐fluorene]‐2,2′,7,7′‐tetramine/Ag/Au structure is improved by adding Sb‐xanthate to the PVK layer without large loss of efficiency. The Sb‐element‐rich layer is observed on top of the PVK layer. From the X‐ray photoelectron spectroscopy (XPS) study, it is concluded that an inorganic SbxOy passivation layer on the PVK layer is prepared by baking the solution of the Sb‐xanthate and the PVK precursor. The inorganic layer prevents moisture and oxygen from penetrating into the PVK layer. This article provides a new method to obtain a passivation layer on a PVK layer by baking a mixture solution in one step for improving solar cell stability. [ABSTRACT FROM AUTHOR]

Trap states at the interface or in bulk perovskite materials critically influence perovskite solar cells performance and long‐term stability. Here, a strategy for efficiently passivating charge traps and mitigating interfacial recombination by SnO2 surface sulfur functionalization is reported, which utilizes xanthate decomposition on the SnO2 surface at low temperature. The results show that functionalized sulfur atoms can coordinate with under‐coordinated Pb2+ ions near the interface. After device fabrication under more than 60 % humidity in ambient air, the efficiency of methylammonium lead iodide (MAPbI3) perovskite solar cells based on sulfur‐functionalized SnO2 increased from 16.56 % to 18.41 % with suppressed hysteresis, which resulted from the accelerated interfacial charge transport kinetics and decreased traps in bulk perovskite by interfacial sulfur functionalization. Additionally, thermally stimulated current studies show the decreased trap density in the shallow trap area after interfacial sulfur functionalization. The interfacial sulfur functionalized solar cells without sealing also exhibited considerable retardation of solar cell degradation with only 10 % degradation after 70 days air storage. This work demonstrates a facile sulfur functionalization strategy by using xanthate decomposition on SnO2 surfaces to obtain highly efficient perovskite solar cells. Inorganic sulfur functionalization has been realized through xanthate annealing on a SnO2 substrate, facilitating electron transport and reducing trap density at the shallow area. The efficiency of the resulting perovskite device was increased significantly with enhanced long‐term stability upon interfacial sulfur functionalization. This method is a simple and highly efficient means of interfacial functionalization with enhanced stability by using inorganic atoms. [ABSTRACT FROM AUTHOR]

Abstract: Perovskite solar cells have attracted considerable attention owing to their easy and low‐cost solution manufacturing process with high power conversion efficiency. However, the fabrication process is usually performed inside a glovebox to avoid moisture, as organometallic halide perovskites are easily dissolved in water. In this study, we propose a one‐step fabrication of high‐quality MAPbI3 perovskite films in around 50 % relative humidity (RH) humid ambient air by using diethyl ether as an antisolvent and methanol as an additive into this antisolvent. Because of the presence of methanol, the water molecules can be efficiently removed from the gaps of the perovskite precursors and the perovskite film formation can be slightly controlled, leading to pinhole‐free and low roughness films. Concurrently, methanol can be used to tune the DMSO ratio in the intermediate perovskite phase to regulate perovskite formation. Planar solar cells fabricated by using this method exhibited the best efficiency of 16.4 % with a reduced current density–voltage hysteresis. This efficiency value is approximately 160 % higher than the devices fabrication by using only diethyl ether treatment. From the impedance measurement, it is also found that the recombination reaction is suppressed when the device is prepared with methanol additive in the antisolvent. This method presents a new path for controlling the growth and morphology of perovskite films in humid climates and laboratories with uncontrolled environments. [ABSTRACT FROM AUTHOR]

The ionic liquid N-butyl-N′-(4-pyridylheptyl)imidazolium bis(trifluoromethane)sulfonimide (BuPyIm-TFSI) was used as a dual-functional additive to improve the electrical properties of the hole-transporting material (HTM) for perovskite solar cells. BuPyIm-TFSI improved the conductivity of HTM and reduced the dark current of the solar cell simultaneously, thereby greatly increasing the power conversion efficiency. [ABSTRACT FROM AUTHOR]

Inorganic lead halide perovskites are attracting increasing attention due to their much better thermal stability than the organic–inorganic hybrid perovskite materials. Thus, the low power conversion efficiency (PCE) is a key issue for the inorganic lead halide perovskite solar cells (PSCs). This is mainly due to their wider bandgap and larger energy loss (Eloss) in the devices. Herein, for solving this issue, a dye molecule‐assisted engineering using the dye of 5,15‐bis(2,6‐dioctoxyphenyl)‐10‐(bis(4‐hexylphenyl)‐amino‐20‐4‐carboxyphenylethynyl)porphyrinato]zinc(II) (YD2‐o‐C8) is demonstrated. Results indicate that this molecule has a bifunctional effect, not only as a co‐sensitization layer for CsPbIBr2 with broader absorption spectrum but also reduces the Eloss by interface passivation. Specifically, the light absorption range of the photoactive layer is broadened from 600 to nearly 680 nm. At the same time, the interfacial charge recombination is highly reduced. After optimizing, the champion PCE is enhanced from 7.02% to 10.13%, and record‐high open‐circuit voltage (VOC) of 1.37 V and short‐circuit currents (JSC) of 12.05 mA cm−2 are achieved. This study opens a simple and efficient way to improve the efficiency of inorganic PSCs. [ABSTRACT FROM AUTHOR]

Despite the eminent performance of the organometallic halide perovskite solar cells (PSCs), the poor stability for humidity and ultraviolet irradiation is still major problem for the commercialization of PSCs. Herein, a novel functional organic compound 1‐(ammonium acetyl)pyrene is successfully introduced for preparing the 2D/3D heterostructured MAPbI3 perovskite. Because of the functional organic pyrene group with high humidity resistance and strong absorption in the ultraviolet region, the 2D/3D perovskite film shows notable stability with no degradation in ≈60% relative humidity after even six months and exhibits a high ultraviolet irradiation stability which keeps nearly no degradation after 1 h in the UV Ozone treatment. Planar PSCs are fabricated in the ≈60% relative humidity air outside glovebox. The champion efficiency of (PEY2PbI4)0.02MAPbI3 perovskite solar cells is 14.7% with nearly no hysteresis which is equal performance of 3D MAPbI3 devices (15.0%). This work presents a new direction for enhancing the solar cells' performance and stability by incorporating a functional organic aromatic compound into the perovskite layer. A novel organic compound 1‐(ammonium acetyl) pyrene is successfully introduced for preparing the 2D/3D heterostructured MAPbI3 perovskite. Because of the functional organic pyrene group with high humidity resistance and strong absorption in the ultraviolet region, the 2D/3D perovskite showed notable stability, comparable photovoltaic performance in humid air atmosphere and ultraviolet irradiation. [ABSTRACT FROM AUTHOR]

The photoelectric properties of nontoxic Sn‐based perovskite make it a promising alternative to toxic Pb‐based perovskite. It has superior photovoltaic performance in comparison to other Pb‐free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi‐interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long‐term stability. [ABSTRACT FROM AUTHOR]

The photoelectric properties of nontoxic Sn‐based perovskite make it a promising alternative to toxic Pb‐based perovskite. It has superior photovoltaic performance in comparison to other Pb‐free counterparts. The facile oxidation of Sn2+ to Sn4+ presents a notable obstacle in the advancement of perovskite solar cells that utilize Sn, as it adversely affects their stability and performance. The study revealed the presence of a Sn4+ concentration on both the upper and lower surfaces of the perovskite layer. This discovery led to the adoption of a bi‐interface optimization approach. A thin layer of Sn metal was inserted at the two surfaces of the perovskite layer. The implementation of this intervention yielded a significant decrease in the levels of Sn4+ and trap densities. The power conversion efficiency of the device was achieved at 14.31 % through the optimization of carrier transportation. The device exhibited operational and long‐term stability. [ABSTRACT FROM AUTHOR]

[Display omitted] All-inorganic perovskite materials (Typically: CsPbI 2 Br) have attracted enormous attention due to their illustrious thermal stability and appropriate bandgap, and their use in perovskite solar cells (PSCs) has been extensively investigated. However, the inevitable defects of the perovskite layer, energy level mismatch between perovskite and carbon electrodes, and the phase instability of CsPbI 2 Br limit the power conversion efficiency (PCE) and stability of carbon-based CsPbI 2 Br PSCs. Herein, we demonstrate a simple and effective strategy for regulating energy level, inhibiting carrier recombination, and delaying the degradation of perovskite by modifying the surface of CsPbI 2 Br with a new type of 2D perovskite Cs 2 PtI 6. The carbon-based CsPbI 2 Br PSCs achieve a higher PCE (13.69 %) than the control device (11.10 %). The excellent matching of the energy level and suppression of charge carrier recombination should be responsible for the improvement in efficiency. Furthermore, the excellent hydrophobic performance of Cs 2 PtI 6 enhances the moisture resistance of the device. This study provides a potential strategy for improving the performance and stability of all-inorganic CsPbI 2 Br PSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] The power conversion efficiency (PCE) of perovskite solar cells (PSCs) is already higher than those of other thin-film photovoltaic technologies, but the stability issue limits their applications. The introduction of sulfur-based compounds in PSCs could contribute to their stability. Herein, sulfur-based compounds have been embedded into each functional layer to stabilize carbon-based PSCs (C-PSCs). Results showed that the simultaneous introduction of sulfur-based compounds could decrease the trap states of perovskite film, enlarge the grain size of perovskite, and accelerate the charge transfer and extraction, leading to an improved performance. Comparing with the device without sulfide (10.77%), all sulfide C-PSCs obtained a PCE of 15.38%. The stability test showed much better resistance to humidity and thermal stress for all sulfide C-PSCs. They could retain 80% of initial PCE after aging about 700 h at relative humidity (RH) 45% ± 10% and 80 °C. [ABSTRACT FROM AUTHOR]

• Improvement interface quality between CsPbI 2 Br perovskite and carbon electrode by Delta-2:2-bis (1,3-dithiazole). • Achievement of high power conversion efficiency (13.78%) with the architecture ITO/SnO 2 /SnCl 2 /CsPbI 2 Br/Carbon. • Increasing the stability of carbon-based CsPbI2Br PSCs because of interface modification. All-inorganic perovskite materials, typically CsPbI 2 Br, have received widespread attention owing to their outstanding thermal stability than that of organic/inorganic hybrid counterparts. However, the power conversion efficiency (PCE) of CsPbI 2 Br perovskite solar cell (PSC) is far lower than its theoretical value. In this study, to further improve the PCE, a sulfur-rich small molecule material (delta-2:2-bis (1,3-dithiazole)), is used to modify the interface between CsPbI 2 Br and carbon electrode. Encouragingly, the carbon-based CsPbI 2 Br PSCs achieve a high PCE of 13.78% than the control of 10.40%, which is the best performance of carbon-based CsPbI 2 Br PSC among the literature report at present. The remarkable reduction of defect density and suppression recombination should be responsible for the PCE improvement. This work proposes a simple and effective strategy to enhance the efficiency of all-inorganic carbon-based CsPbI 2 Br PSCs. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have attracted a lot of attention from researchers as the most promising photovoltaic devices due to their outstanding power conversion efficiency (PCE) and low-cost. Although the PSC have reached a PCE over 25%, the interface between the perovskite and hole transport layer (HTL) still is a crucial factor limiting higher PCE and long-term stability. In this work, we choose an organic molecule Bis(trifluoromethyl)benzo amide (BTFZA) to passivate defects at the perovskite/HTL interface. Owing to a strong interaction with uncoordinated Pb2+, the BTFZA effectively passivated the surface defects, remarkably promoted carrier transportation. As a result, the perovskite device based on BTFZA surface modification showed a PCE increase of 16.4% over the control device. Especially, the fill factor (FF) and the open-circuit voltage (V OC) of the modified device increased significantly. In addition, the unencapsulated BTFZA-modified device maintains better PCE compared to the control device after aging for over 600 h in ambient air with extreme humidity and temperature conditions. Results suggested that the introduction of BTFZA is an effective way to regulate the surface of perovskite film aiming at highly efficient and stable perovskite solar cells. The successful application of surface passivation strategy can effectively improve the efficiency of perovskite solar cells. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract In recent years, attention is increasingly paid to developing layered two-dimensional perovskites due to their superior environmental stability compare with their three-dimensional analogues. However, two-dimensional perovskite based solar cells usually give unsatisfactory photovoltaic performance due to large numbers of defects in the process of crystallinity. Many groups investigate multiple approaches to improve the crystalline quality so far. Here, we systematically investigate the influence of temperature on two-dimensional (PEA) 2 (MA) 2 Pb 3 I 10 perovskite films crystallinity based on hot-casting and post-annealing. The crystallization of (PEA) 2 (MA) 2 Pb 3 I 10 in the case of hot-casting has better crystallinity than post-annealing and discover the thermal annealing and solvent-assisted mass transfer are very important in the process of crystallization based on two-dimensional perovskite. As a result, the devices obtain a highest power conversion efficiency of 5.57% at 100 °C (hot-casting) by optimizing heating temperature of the substrate and the hot-casting two-dimensional (PEA) 2 (MA) 2 Pb 3 I 10 films and devices display superior ambient stability. This work provides an important reference for further improve the crystallization of two-dimensional perovskite film. Highlights • 3D and 2D perovskites have different annealing procedures during crystallization. • Hot-casting preferred by 2D perovskite is assisted by both solvent and heating. • The influence of hot-casting and post-annealing on 2D perovskite is carried out. [ABSTRACT FROM AUTHOR]

Organolead halide perovskite is regarded as the most promising light-harvesting material for next-generation solar cells; however, the intrinsic instability and toxicity of lead are still of great concern. Bismuth is ecofriendly and has electronic properties similar to those of lead, which has gradually attracted interest for optoelectronic applications. However, the valence state of bismuth is different from that of lead, eliminating the possibility of replacing lead by bismuth in organolead halide perovskites. To address this matter, one feasible strategy is to construct B -site double perovskites by the combination of Bi 3+ and B + in 1:1 ratio. In this work, lead-free halide double perovskites of the form Cs 2 Na BX 6 ( B = Sb, Bi; X  = Cl, Br, I) were investigated by first-principles calculations. The electronic properties, optical absorption coefficients, and thermodynamic stability of these compounds were investigated to ascertain their potential application in solar energy conversion. The results provide theoretical support for the exploration of lead-free perovskite materials in potential optoelectronic applications. [ABSTRACT FROM AUTHOR]

Hybrid organic/inorganic perovskite solar cells (PVSCs) are promising alternatives to traditional photovoltaic devices because of their low cost, high power conversion efficiency, and simple production process. Therefore, achieving a low-temperature and high-efficiency procedure is necessary to realize the large-scale production of PVSCs. This study developed a facile low-temperature process (70 °C) for the synthesis of anatase TiO 2 thin films on the FTO substrate through an in situ growth method. The as-synthesized anatase TiO 2 thin films were applied on efficient compact layers of all low-temperature (sub-100 °C)-processed PVSCs. Under optimization, the achieved low-temperature PVSC device exhibited a champion conversion efficiency of up to 10.33%, with excellent repeatability and negligible hysteresis. Results revealed that fast electron extraction and transfer between perovskite and TiO 2 films and effective suppression of charge recombination are the main attributes for the excellent performance of the PVSC device. This work provides a new alternative to achieve low-temperature and high-efficiency photovoltaic devices. [ABSTRACT FROM AUTHOR]

Active composite layers of bismuth triiodide (BiI 3 ) and lead-free (CH 3 NH 3 ) 3 Bi 2 I 9 (MBI) perovskite were prepared using a simple chemical solution method under ambient conditions for thin-film solar cells. Results of X-ray diffraction and scanning electron microscopy indicated that the crystallization and surface morphologies of the composite films varied with perovskite contents. Multi-absorption was observed in the composite films due to the bandgap difference between BiI 3 and MBI perovskite. Moreover, band bending at the BiI 3 -perovskite interfaces resulted in the realignment of energy levels in the composite films, and this phenomenon was beneficial to the efficient injection of excited electrons from the active layers into the TiO 2 layers. Accordingly, due to the optimized crystallization and realigned energy level, when 20% of MBI perovskite was introduced into the active layers, the open-circuit voltage obviously increased from 0.44 V to 0.57 V in the (BiI 3 ) 0.8 (MBI) 0.2 composites solar cells, enhancing their power conversion efficiency by 67% compared with that in pure BiI 3 solar cell. This study developed a new route for designing more efficient lead-free solar cells. [ABSTRACT FROM AUTHOR]

Lead free double perovskites La 2 NiMnO 6 were first studied for potential application on solar cells. The rhombohedral and the monoclinic La 2 NiMnO 6 , with B -site of Ni 3+ /Mn 3+ , were respectively formed under different synthesizing conditions. The experimental results show that the monoclinic La 2 NiMnO 6 sample has a band gap of 1.4 eV and valence band of −5.8 eV, on the other hand, the respective values for rhombohedral sample are 1.2 eV and −5.7 eV. The density function theory calculation demonstrates that the calculated band gap for the monoclinic La 2 NiMnO 6 is larger than that for the rhombohedral one. However, the electronic structures for these La 2 NiMnO 6 are found very similar to each other. Our combined experimental and theoretical studies indicate that, from the aspects of band gaps and energy levels, double perovskite La 2 NiMnO 6 of monoclinic phase could be a better candidate than that of rhombohedral phase for light harvesting. [ABSTRACT FROM AUTHOR]

Electronic and optical properties of double perovskite Sr 2 MMoO 6 (M=Mg, Ca, and Zn) were studied using density functional theory. The double perovskites Sr 2 MgMoO 6 and Sr 2 CaMoO 6 exhibited the direct band gap whereas Sr 2 ZnMoO 6 was found to be indirect band gap material. The valence band maxima consisted mainly of oxygen 2p orbitals, whereas the conduction band minima was composed of hybridization between the B-site of Mo 4d and O 2p orbitals. The on-site Coulomb interaction was examined in terms of the influence of the transition metals׳ d orbitals on the electronic properties of the double perovskites. The dielectric functions and the absorption coefficients were studied from the ground electronic states. These results demonstrated that substituting the B-site elements in double perovskites is a potential method to tune the electronic structure for absorbing visible light for applications in inorganic perovskite solar cells. [ABSTRACT FROM AUTHOR]

Doping a hybrid perovskite semiconductor with metal elements offers an effective means of adjusting its photoelectric properties. To give one example, it has been found that adding lanthanide elements such as Europium (Eu) and Samarium (Sm) into a perovskite layer enhances the photovoltaic performance and photothermal stability of perovskite solar cells. In this study, we therefore added different Praseodymium (Pr)/Lead (Pb) ratios from 0% to 1% to perovskite films in a precursor solution of tri-cation perovskite. We found the photoelectric properties and device performance of perovskite solar cells doped with 0.25% Praseodymium ion (Pr3+) to be significantly improved, with a champion power conversion efficiency (PCE) of 18.56% obtained. Furthermore, the stability of perovskite solar cells (PSCs) with 0.25% Pr3+ doping improved effectively. Overall, with Pr3+ doping, the carrier mobility was dramatically enhanced, and the carrier recombination effectively hindered. These results therefore indicate that Pr3+ doping causes the perovskite to produce lattice shrinkage. As such, the findings shed light on a fresh dopant engineering tactic for fabricating high performance perovskite solar cells. [Display omitted] • Via praseodymium ions (Ⅲ) doping, the perovskite film exhibited excellently enhanced carrier extraction ability. • The PCE of praseodymium chloride doped PSC were improved with better fill factor. • The stability of PSCs was greatly improved by praseodymium ions (Ⅲ) doping. [ABSTRACT FROM AUTHOR]

All-inorganic CsPbI 2 Br perovskite material has attracted enormous attention for high-performance photovoltaics due to its excellent thermal stability and suitable bandgap. Furthermore, carbon-based CsPbI 2 Br perovskite solar cells (C-PSCs) not only further improve the thermal and moisture stability of the devices but also reduce production costs and simplify procedure processes. However, the usage of carbon electrodes introduces new problems, such as poor interface contact and energy level mismatch. Herein, the N-phenylthiourea (PTU) with S atom and N-phenylurea (PU) with O atom are applied for interface modification materials in C-PSCs. The atoms S and O can combine with Pb and enhance perovskite crystallinity as well as manage the energy level. Meanwhile, after passivation of PTU and PU, the defect state density of the perovskite layer is significantly reduced, thereby inhibiting the recombination of carriers. The V oc of the device with PTU increases from 1.12 V to 1.22 V, 9% improvement over the control device. The efficiency of CsPbI 2 Br C-PSCs is improved from 10.29% to 13.01% after modification. Furthermore, the stability of the device has been improved. This study provides a strategy for developing highly efficient and stable C-PSCs. [Display omitted] • PTU aligns the energy level between CsPbI 2 Br and carbon. • PTU optimizes CsPbI 2 Br film quality and device stability. • It achieves a champion PCE 13.01% based on carbon-based CsPbI 2 Br PSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Cs 2 PtI 6 is proposed as a multifunction perovskite modifier. • The perovskite crystal quality is remarkable improved. • The recombination of charge carriers is dramatically suppressed. • A superb PCE of 23.56% is achieved with planar architecture. • Less than 10% degradation of initial PCE is achieved. The planar organic–inorganic hybrid perovskite solar cells (PSCs) have in recent years had remarkable success due to their superior optoelectronic performance. However, their power conversion efficiency is significantly inferior compared to mesoporous structure PSCs. Unlike most other advances focusing on non-perovskite materials to improve device performance, herein a multifunctional double perovskite material, Cs 2 PtI 6 , is proposed as the grain boundary modifier of organic–inorganic hybrid perovskite films. Results show three main benefits of introducing Cs 2 PtI 6 into perovskite films: (1) it prompts growth of perovskite crystals, resulting in improved crystallinity and enlarged crystals; (2) it suppresses the trap assisted recombination at grain boundaries thanks to the formation of heterojunction and interface passivation; (3) it raises the efficiency of carrier collection and transport at grain boundaries owing to the high carrier mobility of Cs 2 PtI 6. Consequently, a PCE of 23.56% is achieved. The unencapsulated devices show less than 10% degradation compared to the initial performance after storage in ambient (≈ 30%) humidity for 2000 h. This study outlines a simple yet effective strategy for boosting the performance of planar PSCs. [ABSTRACT FROM AUTHOR]