Perovskite solar cells (PSC) with efficiencies > 20% have only been realized with highly expensive archetype organic hole transporting materials that can impede the large-scale deployment of PSC. Here we demonstrate PSCs achieving stabilized efficiencies of 20.3% with CuSCN as hole electron extraction layer. We developed a new method for the solution deposition of compact and highly conformal CuSCN layers that afford fast carrier extraction and collection. We also show that the notorious instability of CuSCN based PSCs is not associated with the CuSCN/perovskite interface but rather originates from the CuSCN/Au contact. By introducing a thin spacer layer between CuSCN and gold layers, the PSCs retained >95% of their initial efficiency after aging for 500 h under full-sun illumination at 60 °C, and >85% of their initial efficiency after aging at 85 °C for 1000 h. Importantly, under both continuous illumination and thermal stress, CuSCN based devices surpass the stability of spiro-OMeTAD based PSCs.One Sentence Summary: A record performance displayed by operationally stable perovskite solar cells employing all-inorganic charge extraction layers was realized after introducing a simple dynamic approach for the deposition of thin and conformal CuSCN layer onto perovskite layer and a thin spacer layer between CuSCN and gold layers, which will foster their large scale deployment.The prominence of organic-inorganic perovskite solar cells (PSC) can be credited to the unprecedented advancement in the power conversion efficiencies (PCEs), realized mostly by tailoring the formation and composition of the absorber layer (1,2). Certified PCEs >20% have been obtained while retaining the electron selective TiO 2 layer and by using either spiroOMeTAD [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene] or a polymerbased PTTA (poly-triarylamine) as the hole-transporting material (HTM) (2,3). However, the cost of these HTMs is prohibitively high for large-scale applications and the long-term operational and thermal instability seems to be associated with the archetype organic HTMs or their ingredients (4). One of the strategies to combat the issues of cost and instability could be the use of inexpensive inorganic hole extraction layers similar to the use of TiO 2 as an electron transporting material (5). However, obtaining stable PCEs >20% with PSCs using inorganic 2 HTMs, such as NiO, CuI, Cs 2 SnI 6 , and CuSCN when subjected to light soaking under realistic operational conditions, i.e., at maximum power point and 60°C has remained a challenge (6-9).The realization of efficiencies > 20% using PSCs with inorganic HTMs remains undoubtedly a key goal to foster the large-scale deployment of PSC. Among various inorganic hole transporting materials, CuSCN is an extremely cheap, abundant p-type semiconductor, that exhibits high hole mobility, a good thermal stability and a well-aligned work function (10). The CuSCN is intrinsically p-doped and transmits light across the entire visible and near infrared spect...

Preventing the degradation of metal perovskite solar cells (PSCs) by humid air poses a substantial challenge for their future deployment. We introduce here a two-dimensional (2D) A2PbI4 perovskite layer using pentafluorophenylethylammonium (FEA) as a fluoroarene cation inserted between the 3D light-harvesting perovskite film and the hole-transporting material (HTM). The perfluorinated benzene moiety confers an ultrahydrophobic character to the spacer layer, protecting the perovskite light-harvesting material from ambient moisture while mitigating ionic diffusion in the device. Unsealed 3D/2D PSCs retain 90% of their efficiency during photovoltaic operation for 1000 hours in humid air under simulated sunlight. Remarkably, the 2D layer also enhances interfacial hole extraction, suppressing nonradiative carrier recombination and enabling a power conversion efficiency (PCE) >22%, the highest reported for 3D/2D architectures. Our new approach provides water- and heat-resistant operationally stable PSCs with a record-level PCE.

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As a result of their attractive optoelectronic properties, metal halide APbI3 perovskites employing formamidinium (FA+) as the A cation are the focus of research. The superior chemical and thermal stability of FA+ cations makes α‐FAPbI3 more suitable for solar‐cell applications than methylammonium lead iodide (MAPbI3). However, its spontaneous conversion into the yellow non‐perovskite phase (δ‐FAPbI3) under ambient conditions poses a serious challenge for practical applications. Herein, we report on the stabilization of the desired α‐FAPbI3 perovskite phase by protecting it with a two‐dimensional (2D) IBA2FAPb2I7 (IBA=iso‐butylammonium overlayer, formed via stepwise annealing. The α‐FAPbI3/IBA2FAPb2I7 based perovskite solar cell (PSC) reached a high power conversion efficiency (PCE) of close to 23 %. In addition, it showed excellent operational stability, retaining around 85 % of its initial efficiency under severe combined heat and light stress, that is, simultaneous exposure with maximum power tracking to full simulated sunlight at 80 °C over 500 h.

Small‐molecule photovoltaic cells using diindenoperylene (DIP) as a new donor material in combination with the fullerene C60 as an electron acceptor are demonstrated. In addition to the successful application in planar and bulk heterojunction devices, a comprehensive analysis including structural studies, the determination of the energy level alignment and electrical transport investigations is given, stressing the correlation between growth conditions, film morphology, and device performance. Due to pronounced crystallinity and a large surface area of DIP films grown at elevated temperature, exceptionally high fill factors of almost 75% are achieved in planar heterojunction cells. Bulk heterojunctions exhibit large‐scale phase separation forming a bicontinuous network of both molecular species, which enables efficient exciton dissociation and charge carrier transport. The high ionization potential of DIP and the favorable energy level alignment with the fullerene C60 yield large open circuit voltages close to 1 V and comparable power conversion efficiencies of about 4% in both cell architectures.