Efficient and carbon-based hole transport layer-free CsPbI2Br planar perovskite solar cells using PMMA modification

Abstract

In this work, planar inorganic perovskite solar cells (PSCs) with the simple structure of glass/ITO/SnO₂/CsPbI₂Br/C have been fabricated. Solution-processed poly(methyl methacrylate) (PMMA) is selected to modify the CsPbI₂Br film. The effects of PMMA modification on the microstructure of the CsPbI₂Br film and the photoelectric properties of inorganic PSCs have been systematically investigated. The concentration of the PMMA solution has been optimized. At the optimal concentration, the modified carbon-based hole transport layer (HTL)-free CsPbI₂Br PSCs demonstrate an improved open-circuit voltage (V_oc) and fill factor (FF), and achieve a champion efficiency of 10.95% with less hysteresis behavior, this being much higher than the 9.14% of the reference PSCs. Moreover, the unencapsulated CsPbI₂Br PSCs modified by PMMA demonstrate improved stability and retain about 95% of their initial efficiency after being exposed to air (relative humidity of 25–35%) for 20 days. The enhanced performance is mainly attributed to the reduced trap state density and suppressed charge recombination. This work provides a simple route to fabricate efficient and stable carbon-based HTL-free inorganic PSCs.