Cesium Iodide Interface Modification for High Efficiency, High Stability and Low Hysteresis Perovskite Solar Cells

• DOI: 10.1016/j.electacta.2017.03.139
• Publication Date: 2017-03-20T18:03:21Z
• Authors: Fei Han; Junsheng Luo; Bowen Zhao; Zhongquan Wan; Ruilin Wang; Chunyang Jia
• Keywords: Passivation; Hysteresis; Caesium; Surface Modification

Abstract Each interface is crucial to perovskite solar cells (PSCs), so the interface modification is often used to improve the PV performances. In this manuscript, an environment-friendly cesium iodide (CsI) interface layer between the mesoporous TiO 2 (mp-TiO 2 ) and the MAPbI 3 perovskite active layer was introduced to improve the PV performances and stabilities of PSCs and significantly reduce hysteresis of the device. After optimizing, the PSC employing a CsI-modified mp-TiO 2 as electron transporting layer (ETL) could obtain a high fill factor (FF) of 0.79 with an increased power conversion efficiency (PCE) of 17.10% and a low hysteresis index (HI) of 0.10 under illumination of AM 1.5G, while FF of 0.75 and PCE of 14.38% for PSC without CsI interface modification. The enhanced PV performances can be attributed to the improved surface morphology of mp-TiO 2 , the lower work function (WF) of TiO 2 , the passivation of surface trap states, the improved perovskite crystallization and reduced grain boundaries. Besides, the reduced WF of TiO 2 results in the enhanced built-in potential, which promotes the charge separation, transport and collection.