Oxidization-Free Spiro-OMeTAD Hole-Transporting Layer for Efficient CsPbI<sub>2</sub>Br Perovskite Solar Cells
Zhu Ma, Zheng Xiao, Qianyu Liu, Dejun Huang, Weiya Zhou, Huifeng Jiang, Zhiqing Yang, Meng Zhang, Wenfeng Zhang, Yuelong Huang
Abstract
The inorganic CsPbI2Br perovskite faces serious challenges of low phase stability and high moisture sensitivity. The moisture controllable process of a hole-transporting layer (HTL) is crucial for the development of stable and efficient inorganic perovskite solar cells (IPSCs). In this work, we proposed an oxidization-free spiro-OMeTAD hole-transport layer (HTL) with a preoxidized spiro-OMeTAD solution to prevent moisture and completely avoid the phase transition of CsPbI2Br from the α-phase to β-phase. The oxidization-free HTL exhibited improved surface hydrophobic properties, smoother morphology, and optimized energy-level alignment compared with a traditional HTL. As a result, the CsPbI2Br-based IPSCs achieved an efficiency of up to 14.2 and 86.6% of the initial power conversion efficiency (PCE) with 2000 h storage. Meanwhile, this oxidization-free HTL was applied in CH3NH3PbI3-based PSCs and obtained 13.8% PCE enhancement, which proved the universality of the solution preoxidization tactic. We believe that the oxidization-free HTL could be an efficient strategy to replace traditional HTLs and can be widely used in perovskite solar cells, especially in moisture-sensitive PSCs.