Although the perovskite solar cells (PSCs) based on organic hole transport materials (HTMs) have demonstrated excellent photovoltaic performance , there are still some obstacles that limiting their future commercialization , one of which is the device stability. Herein, we first report that depositing a (200) orientated PbS thin film upon organic HTMs as buffer layer can significantly enhance the stability and improve the performance of PSCs. The superior hole extraction efficiency of spiro-OMeTAD/PbS bilayer can balance the charge transfer and the hydrophobic nature of PbS could avoid the permeation of moisture. As a result, the PSCs with PbS buffer layer exhibited a better photovoltaic performance (a champion power conversion efficiency of 19.58%) with respect to the reference cells (18.79%), and maintained almost 100% of its initial PCE after 1000 h stored in ambient air. Furthermore, when suffer from some more severe conditions, the device with PbS retained 56% of its initial PCE after 96 h annealing at 85 °C, while only 25% for the reference cells. Our results provide a simple method to avoid the weakness of organic HTMs, and suggest that PbS thin film could be an alternative buffer layer material in PSCs to simultaneously improve the device stability and photovoltaic performance.
Xiaobin Zhan,Xuning Zhang,Zhiyong Liu,Chen Chen,Lingxian Kong,Shulan Jiang,Shuang Xi,Guanglan Liao,Xingyue Liu
All-inorganic CsPbCl3 perovskite in ultraviolet (UV) detection is drawing increasing interest owing to its UV-matchable optical band gap, ultrahigh UV stability, and superior inherent optoelectronic properties. Almost all of the reported CsPbCl3 photodetectors employ CsPbCl3 nano- or microstructures as sensitive components, while CsPbCl3 polycrystalline film-based self-powered photodetectors are rarely studied on account of the terrible precursor solubility. Herein, a novel sequential vapor-deposition technique is demonstrated to fabricate CsPbCl3 polycrystalline film for the first time. High-quality CsPbCl3 films with excellent optical, electronic, and morphological features are obtained. A self-powered photodetector based on the CsPbCl3 film is constructed without any charge transport layer, showing a high UV detection performance. A thin p-type PbS buffer layer is further introduced to passivate the surface defects of the CsPbCl3 layer and decrease the interfacial energy barrier by forming a type-II heterojunction, contributing to a faster hole extraction rate and a suppressed dark current level. The best-performing device achieves an ultrafast response time of 1.92 μs, an ultrahigh on/off ratio of 2.22 × 105, and a responsivity of 0.22 A/W upon 375 nm UV illumination at 0 V bias. This comprehensive performance is the best among all of the CsPbCl3 photodetectors reported to date. The as-prepared photodetectors also present an eminent UV irradiation and long-term durability in ambient air. Furthermore, a large-area and uniform 625-pixel UV image sensor is fabricated and attains a prominent imaging capability. Our work opens a new avenue for the scalable production of CsPbCl3-based optoelectronics.
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