A Novel Anion Doping for Stable CsPbI2Br Perovskite Solar Cells with an Efficiency of 15.56% and an Open Circuit Voltage of 1.30 V

The Cs‐based inorganic perovskite solar cells (PSCs), such as CsPbI₂Br, have made a striking breakthrough with power conversion efficiency (PCE) over 16% and potential to be used as top cells for tandem devices. Herein, I^? is partially replaced with the acetate anion (Ac^?) in the CsPbI₂Br framework, producing multiple benefits. The Ac^? doping can change the morphology, electronic properties, and band structure of the host CsPbI₂Br film. The obtained CsPbI_2?x Br(Ac)_x perovskite films present lower trap densities, longer carrier lifetimes, and fast charge transportation compared to the host CsPbI₂Br films. Interestingly, the CsPbI_2?x Br(Ac)_x PSCs exhibit a maximum PCE of 15.56% and an ultrahigh open circuit voltage (V_oc) of 1.30 V without sacrificing photocurrent. Notably, such a remarkable V_oc is among the highest values of the previously reported CsPbI₂Br PSCs, while the PCE far exceeds all of them. In addition, the obtained CsPbI_2?x Br(Ac)_x PSCs exhibit high reproducibility and good stability. The stable CsPbI_2?x Br(Ac)_x PSCs with high V_oc and PCE are desirable for tandem solar cell applications.     

Incorporating CsF into the PbI2 Film for Stable Mixed Cation‐Halide Perovskite Solar Cells

Adding a small amount of CsI into mixed cation‐halide perovskite film via a one‐step method has been demonstrated as an excellent strategy for high‐performance perovskite solar cells (PSCs). However, the one‐step method generally relies on an antisolvent washing process, which is hard to control and not suitable for fabricating large‐area devices. Here, CsF is employed and Cs is incorporated into perovskite film via a two‐step method. It is revealed that CsF can effectively diffuse into the PbI₂ seed film, and drastically enhances perovskite crystallization, leading to high‐quality Cs‐doped perovskite film with a very long photoluminescence carrier lifetime (1413 ns), remarkable light stability, thermal stability, and humidity stability. The fabricated PSCs show power conversion efficiency (PCE) of over 21%, and they are highly thermally stable: in the aging test at 60 °C for 300 h, 96% of the original PCE remains. The CsF incorporation process provides a new avenue for stable high‐performance PSCs.     

Fusing Nanowires into Thin Films: Fabrication of Graded‐Heterojunction Perovskite Solar Cells with Enhanced Performance

Perovskite solar cells (PSCs) have recently experienced a rapid rise in power conversion efficiency (PCE), but the prevailing PSCs with conventional mesoscopic or planar device architectures still contain nonideal perovskite/hole‐transporting‐layer (HTL) interfaces, limiting further enhancement in PCE and device stability. In this work, CsPbBr₃ perovskite nanowires are employed for modifying the surface electronic states of bulk perovskite thin films, forming compositionally‐graded heterojunction at the perovskite/HTL interface of PSCs. The nanowire morphology is found to be key to achieving lateral homogeneity in the perovskite film surface states resulting in a near‐ideal graded heterojunction. The hidden role of such lateral homogeneity on the performance of graded‐heterojunction PSCs is revealed for the first time. The resulting PSCs show high PCE up to 21.4%, as well as high operational stability, which is superior to control PSCs fabricated without CsPbBr₃‐nanocrystals modification and with CsPbBr₃‐nanocubes modification. This study demonstrates the promise of controlled hybridization of perovskite nanowires and bulk thin films for more efficient and stable PSCs.     

The Synergism of DMSO and Diethyl Ether for Highly Reproducible and Efficient MA0.5FA0.5PbI3 Perovskite Solar Cells

Composition and film quality of perovskite are crucial for the further improvement of perovskite solar cells (PSCs), including efficiency, reproducibility, and stability. Here, it is demonstrated that by simply mixing 50% of formamidinium (FA⁺) into methylammonium lead iodide (MAPbI₃), a highly crystalline, stable phase, and compact, polycrystalline grain morphology perovskite is formed by using a solvent‐mediated phase transformation process via the synergism of dimethyl sulfoxide and diethyl ether, which shows long carrier lifetime, low trap state density, and a record certified 21.8% power conversion efficiency (PCE) in pure‐iodide, alkaline‐metal‐free MA_0.5FA_0.5PbI₃ perovskite‐based PSCs. These PSCs show very high operational stability, with 85% PCE retention upon 1000 h 1 Sun intensity illumination. A 17.33% PCE module (6.5 × 7 cm²) is also demonstrated, attesting to the scalability of such devices.     

Controllable Perovskite Crystallization via Antisolvent Technique Using Chloride Additives for Highly Efficient Planar Perovskite Solar Cells

The presence of surface and grain boundary defects in organic–inorganic halide perovskite films can be detrimental to both the performance and operational stability of perovskite solar cells (PSCs). Here, the effect of chloride additives is studied on the bulk and surface defects of the mixed cation and halide PSCs. It is found that using an antisolvent technique, the perovskite film is divided into two layers, i.e., a bottom layer with large grains and a thin capping layer with small grains. The addition of formamidinium chloride (FACl) into the precursor solution removes the small‐grained perovskite capping layer and suppresses the formation of bulk and surface defects, providing a perovskite film with enhanced crystallinity and large grain size of over 1 µm. Time‐resolved photoluminescence measurements show longer lifetimes for perovskite films modified by FACl and subsequently passivated by 1‐adamantylamine hydrochloride as compared to the reference sample. Impedance spectroscopy measurements show that these treatments reduce the recombination in the PSCs, leading to a champion device with power conversion efficiency (PCE) of 21.2%, an open circuit voltage of 1152 mV and negligible hysteresis. The Cl treated PSC also shows improved operational stability with only 12% PCE loss after 700 h under continuous illumination.     

Precursor Engineering for Ambient‐Compatible Antisolvent‐Free Fabrication of High‐Efficiency CsPbI2Br Perovskite Solar Cells

High temperature stable inorganic CsPbX₃ (X: I, Br, or mixed halides) perovskites with their bandgap tailored by tuning the halide composition offer promising opportunities in the design of ideal top cells for high‐efficiency tandem solar cells. Unfortunately, the current high‐efficiency CsPbX₃ perovskite solar cells (PSCs) are prepared in vacuum, a moisture‐free glovebox or other low‐humidity conditions due to their poor moisture stability. Herein, a new precursor system (HCOOCs, HPbI₃, and HPbBr₃) is developed to replace the traditional precursors (CsI, PbI₂, and PbBr₂) commonly used for solar cells of this type. Both the experiments and calculations reveal that a new complex (HCOOH?Cs⁺) is generated in this precursor system. The new complex is not only stable against aging in humid air ambient at 91% relative humidity, but also effectively slows the perovskite crystallization, making it possible to eliminate the popular antisolvent used in the perovskite CsPbI₂Br film deposition. The CsPbI₂Br PSCs based on the new precursor system achieve a champion efficiency of 16.14%, the highest for inorganic PSCs prepared in ambient air conditions. Meanwhile, high air stability is demonstrated for an unencapsulated CsPbI₂Br PSC with 92% of the original efficiency remaining after more than 800 h aging in ambient air.     

Morphology Controlling of All‐Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

All‐inorganic cesium lead halide (CsPbX₃) perovskites have emerged as promising photovoltaic materials owing to their superior thermal stability compared to traditional organic–inorganic hybrid counterparts. However, the CsPbX₃ perovskites generally need to be prepared at high‐temperature, which restricts their application in multilayer or flexible solar cells. Herein, the formation of CsPbX₃ perovskites at room‐temperature (RT) induced by dimethylsulphoxide (DMSO) coordination is reported. It is further found that a RT solvent (DMSO) annealing (RTSA) treatment is valid to control the perovskite crystallization dynamics, leading to uniform and void‐free films, and consequently a maximum power conversion efficiency (PCE) of 6.4% in the device indium tin oxide (ITO)/NiO _x /RT‐CsPbI₂Br/C₆₀/Bathocuproine (BCP)/Ag, which is, as far as it is known, the first report of RT solution‐processed CsPbX₃‐based perovskite solar cells (PSCs). Moreover, the efficiency can be boosted up to 10.4% by postannealing the RTSA‐treated perovskite film at an optimal temperature of 120 °C. Profiting from the moderate temperature, flexible PSCs are also demonstrated with a maximum PCE of 7.3% for the first time. These results may stimulate further development of all‐inorganic CsPbX₃ perovskites and their application in flexible electronics.     

Enhancing Optical,Electronic, Crystalline,and Morphological Properties of Cesium Lead Halide by Mn Substitution for High‐Stability All‐Inorganic Perovskite Solar Cells with Carbon Electrodes

In this work all‐inorganic perovskite CsPbIBr₂ are doped with Mn to compensate their shortcomings in band structure for the application of perovskite solar cells (PSCs). The novel Mn‐doped all‐inorganic perovskites, CsPb_1?xMn_xI_1+2xBr_2?2x, are prepared in ambient atmosphere. As the concentration of Mn²⁺ ions increases, the bandgaps of CsPb_1?xMn_xI_1+2xBr_2?2x decrease from 1.89 to 1.75 eV. Additionally, when the concentration of Mn dopants is appropriate, this novel Mn‐doped all‐inorganic perovskite film shows better crystallinity and morphology than its undoped counterpart. These advantages alleviate the energy loss in hole transfer and facilitate the charge‐transfer in perovskites, therefore, PSCs based on these novel CsPb_1?xMn_xI_1+2xBr_2?2x perovskite films display better photovoltaic performance than the undoped CsPbIBr₂ perovskite films. The reference CsPbIBr₂ cell reaches a power conversion efficiency (PCE) of 6.14%, comparable with the previous reports. The CsPb_1?xMn_xI_1+2xBr_2?2x cells reach the highest PCE of 7.36% (when x = 0.005), an increase of 19.9% in PCE. Furthermore, the encapsulated CsPb_0.995Mn_0.005I_1.01Br_1.99 cells exhibit good stability in ambient atmosphere. The storage stability measurements on the encapsulated PSCs reveal that PCE is dropped by only 8% of the initial value after >300 h in ambient. Such improved efficiency and stability are achieved using low‐cost carbon electrodes (without expensive hole transport materials and Au electrodes).     

High‐Efficiency CsPbI2Br Perovskite Solar Cells with Dopant‐Free Poly(3‐hexylthiophene) Hole Transporting Layers

CsPbI₂Br is emerging as a promising all‐inorganic material for perovskite solar cells (PSCs) due to its more stable lattice structure and moisture resistance compared to CsPbI₃, although its device performance is still much behind this counterpart. Herein, a preannealing process is developed and systematically investigated to achieve high‐quality CsPbI₂Br films by regulating the nucleation and crystallization of perovskite. The preannealing temperature and time are specifically optimized for a dopant‐free poly(3‐hexylthiophene) (P3HT)‐based device to target dopant‐induced drastic performance degradation for spiro‐OMeTAD‐based devices. The resulting P3HT‐based device exhibits comparable power conversion efficiency (PCE) to spiro‐OMeTAD‐based devices but much enhanced ambient stability with over 95% PCE after 1300 h. A diphenylamine derivative is introduced as a buffer layer to improve the energy‐level mismatch between CsPbI₂Br and P3HT. A record‐high PCE of 15.50% for dopant‐free P3HT‐based CsPbI₂Br PSCs is achieved by alleviating the open‐circuit voltage loss with the buffer layer. These results demonstrate that the preannealing processing together with a suitable buffer layer are applicable strategies for developing dopant‐free P3HT PSCs with high efficiency and stability.     

Adamantanes Enhance the Photovoltaic Performance and Operational Stability of Perovskite Solar Cells by Effective Mitigation of Interfacial Defect States

Passivation of electronic defects is an effective strategy to boost the performance and operational stability of perovskite solar cells (PSCs). Identifying molecular materials that achieve this purpose is a key target of current research efforts. Here, adamantane (AD) and 1‐adamantylamine (ADA) are introduced as molecular modulators to abate electronic defects present within the bulk and at the perovskite–hole conductor interface. To this effect, the modulator is added either into the antisolvent (AS) to precipitate it together with the perovskite (AS method) or they are spin coated (SC) onto its surface (SC method). Time‐resolved photoluminescence measurements show substantially longer lifetimes for perovskite films treated with AD and ADA compared to the reference sample. In line with this observation, it is found that the presence of AD and ADA molecules at the interface between the perovskite film and the hole conductor increases all photovoltaic metrics, in particular the open circuit photovoltage (V _oc) as well as the operational stability of the PSC.     

Simultaneous Improved Performance and Thermal Stability of Planar Metal Ion Incorporated CsPbI2Br All‐Inorganic Perovskite Solar Cells Based on MgZnO Nanocrystalline Electron Transporting Layer

The high thermal stability and facile synthesis of CsPbI₂Br all‐inorganic perovskite solar cells (AI‐PSCs) have attracted tremendous attention. As far as electron‐transporting layers (ETLs) are concerned, low temperature processing and reduced interfacial recombination centers through tunable energy levels determine the feasibility of the perovskite devices. Although the TiO₂ is the most popular ETL used in PSCs, its processing temperature and moderate electron mobility hamper the performance and feasibility. Herein, the highly stable, low‐temperature processed MgZnO nanocrystal‐based ETLs for dynamic hot‐air processed Mn²⁺ incorporated CsPbI2Br AI‐PSCs are reported. By holding its regular planar “n–i–p” type device architecture, the MgZnO ETL and poly(3‐hexylthiophene‐2,5‐diyl) hole transporting layer, 15.52% power conversion efficiency (PCE) is demonstrated. The thermal‐stability analysis reveals that the conventional ZnO ETL‐based AI‐PSCs show a serious instability and poor efficiency than the Mg²⁺ modified MgZnO ETLs. The photovoltaic and stability analysis of this improved photovoltaic performance is attributed to the suitable wide‐bandgap, low ETL/perovskite interface recombination, and interface stability by Mg²⁺ doping. Interestingly, the thermal stability analysis of the unencapsulated AI‐PSCs maintains >95% of initial PCE more than 400 h at 85 °C for MgZnO ETL, revealing the suitability against thermal degradation than conventional ZnO ETL.     

Efficient and Highly Air Stable Planar Inverted Perovskite Solar Cells with Reduced Graphene Oxide Doped PCBM Electron Transporting Layer

Reduced graphene oxide (rGO) is added in the [6,6]‐Phenyl‐C61‐butyric acid methyl ester (PCBM) electron transport layer (ETL) of planar inverted perovskite solar cells (PSCs), resulting in a power conversion efficiency (PCE) improvement of ≈12%, with a hysteresis‐free PCE of 14.5%, compared to 12.9% for the pristine PCBM based device. The universality of the method is demonstrated in PSCs based on CH₃NH₃PbI_3?x Cl_x and CH₃NH₃PbI₃ perovskites, deposited through one step and two step spin coating process, respectively. After a comprehensive spectroscopic characterization of both devices, it is clear that the introduction of rGO in PCBM ETL results in an important increase of the ETL conductivity, together with reduced series resistance and surface roughness. As a result, a significant photoluminescence quenching of such perovskite/ETL is observed, confirming the increased measured short circuit current density. Transient absorption measurements reveal that in the rGO‐based device, the relaxation process of the excited electrons is significantly faster compared to the reference, which implies that the charge injection rate is significantly faster for the first. Furthermore, the light soaking effect is significantly reduced. Finally, aging measurements reveal that the rGO stabilizes the ELT/perovskite interface, which results in the stabilization of perovskite crystal structure after prolonged illumination.     

Highly stable and Efficient Perovskite Solar Cells Based on FAMA‐Perovskite‐Cu:NiO Composites with 20.7% Efficiency and 80.5% Fill Factor

To solve critical issues related to device stability and performance of perovskite solar cells (PSCs), FA_0.026MA_0.974PbI_3?yCl_y‐Cu:NiO (formamidinium methylammonium (FAMA)‐perovskite‐Cu:NiO) and Al₂O₃/Cu:NiO composites are developed and utilized for fabrication of highly stable and efficient PSCs through fully‐ambient‐air processes. The FAMA‐perovskite‐Cu:NiO composite crystals prepared without using any antisolvents not only improve the perovskite film quality with large‐size crystals and less grain boundaries but also tailor optical and electronic properties and suppress charge recombination with reduction of trap density. A champion device based on the composites as light absorber and Al₂O₃/Cu:NiO interfacial layer between electron transport layer and active layer yields power conversion efficiency (PCE) of 20.67% with V_OC of 1.047 V, J_SC of 24.51 mA cm^?2, and fill factor of 80.54%. More importantly, such composite‐based PSCs without encapsulation show significant enhancement in long‐term air‐stability, thermal‐ and photostability with retaining 97% of PCE over 240 d under ambient conditions (25–30 °C, 45–55% humidity).     

Rapid Aqueous Spray Fabrication of Robust NiOx: A Simple and Scalable Platform for Efficient Perovskite Solar Cells

Organometal halide perovskites have powerful intrinsic potential to drive next‐generation solar technology, but their insufficient thermomechanical reliability and unproven large‐area manufacturability limit competition with incumbent silicon photovoltaics. This work addresses these limitations by leveraging large‐area processing and robust inorganic hole transport layers (HTLs). Inverted perovskite solar cells utilizing NiO_x HTLs deposited by rapid aqueous spray‐coating that outperform spin‐coated NiO_x and lead to a 5× improvement in the fracture energy (G_c), a primary metric of thermomechanical stability, are presented. The morphology, chemical composition, and optoelectronic properties of the NiO_x films are characterized to understand and optimize compatibility with an archetypal double cation perovskite, Cs_.17FA_.83Pb(Br_.17I_.83)₃. Perovskite solar cells with sprayed NiO_x show higher photovoltaic performance, exhibiting up to 82% fill factor and 17.7% power conversion efficiency (PCE)—the highest PCE reported for inverted cell with scalable charge transport layers—as well as excellent stability under full illumination and after 4000 h aging in inert conditions at room temperature. By utilizing open‐air techniques and aqueous precursors, this combination of robust materials and low‐cost processing provides a platform for scaling perovskite modules with long‐term reliability.     

Crystallinity Preservation and Ion Migration Suppression through Dual Ion Exchange Strategy for Stable Mixed Perovskite Solar Cells

The mixed perovskite (FAPbI₃)_1?x (MAPbBr₃)_x , prepared by directly mixing different perovskite components, suffers from phase competition and a low‐crystallinity character, resulting in instability, despite the high efficiency. In this study, a dual ion exchange (DIE) method is developed by treating as‐prepared FAPbI₃ with methylammonium brodide (MABr)/tert‐butanol solution. The converted perovskite thin film shows an optimized absorption edge at 800 nm after reaction time control, and the high crystallinity can be preserved after MABr incorporation. More importantly, it is found that the threshold electrical field to initiate ion migration is greatly increased in DIE perovskite thin film because excess MABr on the surface can effectively heal structural defects located on grain boundaries during the ion exchange process. It contributes to the over‐one‐month moisture stability under ≈65% room humidity (RH) and greatly enhanced light stability for the bare perovskite film. As a result of preserved high crystallinity and simultaneous grain boundary passivation, the perovskite solar cells fabricated by the DIE method demonstrate reliable reproducibility with an average power conversion efficiency (PCE) of 17% and a maximum PCE of 18.1%, with negligible hysteresis.     

Efficient Passivation with Lead Pyridine‐2‐Carboxylic for High‐Performance and Stable Perovskite Solar Cells

Stability has become the main obstacle for the commercialization of perovskite solar cells (PSCs) despite the impressive power conversion efficiency (PCE). Poor crystallization and ion migration of perovskite are the major origins of its degradation under working condition. Here, high‐performance PSCs incorporated with pyridine‐2‐carboxylic lead salt (PbPyA₂) are fabricated. The pyridine and carboxyl groups on PbPyA₂ can not only control crystallization but also passivate grain boundaries (GBs), which result in the high‐quality perovskite film with larger grains and fewer defects. In addition, the strong interaction among the hydrophobic PbPyA₂ molecules and perovskite GBs acts as barriers to ion migration and component volatilization when exposed to external stresses. Consequently, superior optoelectronic perovskite films with improved thermal and moisture stability are obtained. The resulting device shows a champion efficiency of 19.96% with negligible hysteresis. Furthermore, thermal (90 °C) and moisture (RH 40–60%) stability are improved threefold, maintaining 80% of initial efficiency after aging for 480 h. More importantly, the doped device exhibits extraordinary improvement of operational stability and remains 93% of initial efficiency under maximum power point (MPP) tracking for 540 h.     

Hot‐Substrate Deposition of Hole‐ and Electron‐Transport Layers for Enhanced Performance in Perovskite Solar Cells

Charge transport layers play an important role in determining the power conversion efficiencies (PCEs) of perovskite solar cells (PSCs). However, it has proven challenging to produce thin and compact charge transport layers via solution processing techniques. Herein, a hot substrate deposition method capable of improving the morphology of high‐coverage hole‐transport layers (HTLs) and electron‐transport layers (ETLs) is reported. PSC devices using HTLs deposited on a hot substrate show improvement in the open‐circuit voltage (V_oc) from 1.041 to 1.070 V and the PCE from 17.00% to 18.01%. The overall device performance is then further enhanced with the hot substrate deposition of ETLs as the V_oc and PCE reach 1.105 V and 19.16%, respectively. The improved performance can be explained by the decreased current leakage and series resistance, which are present in PSCs with rough and discontinuous HTLs and ETLs.     

Cold Antisolvent Bathing Derived Highly Efficient Large‐Area Perovskite Solar Cells

Scaling large‐area solar cells is in high demand for the commercialization of perovskite solar cells (PSCs) with a high power‐conversion efficiency (PCE). However, few roll‐to‐roll‐compatible deposition methods for the formation of highly oriented uniform perovskite films are reported. Herein, a facile cold antisolvent bathing approach compatible with large‐area fabrication is introduced. The wet precursor films are submerged in a cold antisolvent bath at 0 °C, and the retarded nucleation and growth kinetics allow highly oriented perovskite to be grown along the [110] and [220] directions, perpendicular to the substrate. The high degree of the preferred crystal orientation benefits the effective charge extraction and reduces the amount of inter‐ and intra‐grain defects inside the perovskite films, improving the PCE from 16.48% (ambient‐bathed solar cell) to 18.50% (cold‐bathed counterpart). The cold antisolvent bathing method is employed for the fabrication of large‐area (8 × 10 cm²) PSCs with uniform photovoltaic device parameters, thereby verifying the scale‐up capability of the method.     

Synergistic Crystal and Interface Engineering for Efficient and Stable Perovskite Photovoltaics

The presence of bulk and surface defects in perovskite light harvesting materials limits the overall efficiency of perovskite solar cells (PSCs). The formation of such defects is suppressed by adding methylammonium chloride (MACl) as a crystallization aid to the precursor solution to realize high‐quality, large‐grain triple A‐cation perovskite films and that are combined with judicious engineering of the perovskite interface with the electron and hole selective contact materials. A planar SnO₂/TiO₂ double layer oxide is introduced to ascertain fast electron extraction and the surface of the perovskite facing the hole conductor is treated with iodine dissolved in isopropanol to passivate surface trap states resulting in a retardation of radiationless carrier recombination. A maximum solar to electric power conversion efficiency (PCE) of 21.65% and open circuit photovoltage (V_oc) of ≈1.24 V with only ≈370 mV loss in potential with respect to the band gap are achieved, by applying these modifications. Additionally, the defect healing enhances the operational stability of the devices that retain 96%, 90%, and 85% of their initial PCE values after 500 h under continuously light illumination at 20, 50, and 65 °C, respectively, demonstrating one of the most stable planar PSCs reported so far.     

Surface Engineering of TiO2 ETL for Highly Efficient and Hysteresis‐Less Planar Perovskite Solar Cell (21.4%) with Enhanced Open‐Circuit Voltage and Stability

Interfacial studies and band alignment engineering on the electron transport layer (ETL) play a key role for fabrication of high‐performance perovskite solar cells (PSCs). Here, an amorphous layer of SnO₂ (a‐SnO₂) between the TiO₂ ETL and the perovskite absorber is inserted and the charge transport properties of the device are studied. The double‐layer structure of TiO₂ compact layer (c‐TiO₂) and a‐SnO₂ ETL leads to modification of interface energetics, resulting in improved charge collection and decreased carrier recombination in PSCs. The optimized device based on a‐SnO₂/c‐TiO₂ ETL shows a maximum power conversion efficiency (PCE) of 21.4% as compared to 19.33% for c‐TiO₂ based device. Moreover, the modified device demonstrates a maximum open‐circuit voltage (V_oc) of 1.223 V with 387 mV loss in potential, which is among the highest reported value for PSCs with negligible hysteresis. The stability results show that the device on c‐TiO₂/a‐SnO₂ retains about 91% of its initial PCE value after 500 h light illumination, which is higher than pure c‐TiO₂ (67%) based devices. Interestingly, using a‐SnO₂/c‐TiO₂ ETL the PCE loss was only 10% of initial value under continuous UV light illumination after 30 h, which is higher than that of c‐TiO₂ based device (28% PCE loss).