用于高效碳基CsPbI2Br太阳能电池的含氧酸盐TiO2/钙钛矿界面：化学吸附诱导的表面电子转移调控能级

Abstract The photovoltaic performance of carbon-based CsPbI 2 Br solar cells is considerably limited by the quality of electron transporting layer (ETL)/perovskite interface. Specifically, the ETL/perovskite interface contains defects such as iodine vacancies. Meantime, the Fermi energy ( E F ) level of ETL is generally much higher than ones of perovskite and transparent conductive oxide (TCO) electrode. The above two issues together contribute to serious charge carrier recombination in devices. Oxyacid salts have been developed to be promising interfacial materials for ETL/perovskite interface, owing to their effective defect passivation and energy level tuning. However, the structure-functionality relationship of these materials has not been well established due to the unclear correlation between interfacial interaction and energy level tuning. Herein, through using CdSO 4 as modifier for TiO 2 ETL and controlling the thickness, we investigate the interfacial interaction and successfully correlates it to energy level tuning. It is shown that the chemically adsorbed SO 4 2- withdraws electrons from TiO 2 . This interaction results in a downshifted E F level for TiO 2 and sets up a surface dipole moment which upshifts the energy band of perovskite. As a result, we obtain improved energy level alignment at both TCO/ETL interface and ETL/perovskite interface. The above effects lead to enhanced electron transport and mitigated charge carrier loss. Therefore, the power conversion efficiency of carbon-based CsPbI 2 Br solar cell is increased from 13.61 % to 15.09 %. Equally noteworthy is the remarkably enhanced environmental stability exhibited by these devices.