Buried interface engineering based on dipolar molecule interlayer for enhancing photovoltaic performance of CsPbIBr2 perovskite solar cells

The buried-interface properties of inorganic perovskite solar cells play a key role in determining the quality of the perovskite film and the charge transfer at the buried interface. Therefore, the structure optimization of buried interfaces through the buried interface engineering is an effective strategy to improve the efficiency and stability of inorganic perovskite solar cells. In this work, 6-amino nicotinic acid (ANA) molecules were employed to modify the buried interface of CsPbIBr2 perovskite solar cells (TiO2/CsPbIBr2 interface). ANA molecules are absorbed on the surface of the TiO2 electron-transport layer through strong interactions between the -COOH group and TiO2, forming an ANA molecule dipolar interlayer at the buried interface of CsPbIBr2 perovskite solar cells. The formation of ANA dipolar interlayer improves the surface wettability of the TiO2 layer by CsPbIBr2 precursor solution, promotes the uniform nucleation and growth of the CsPbIBr2 perovskite, enhances the perovskite quality, and ameliorates the interface contact. Meanwhile, the formation of the ANA dipolar interlayer increases the work functions of the TiO2 layer, leading to the formation of an optimized energy level structure for electron transport at the buried interface between the TiO2 layer and CsPbIBr2 perovskite. Consequently, the assembled carbon-based CsPbIBr2 perovskite solar cells without hole-transport layer achieve a high power conversion efficiency of 10.98%, which is 37% higher than the efficiency of the control device. In addition, the CsPbIBr2 perovskite solar cell with ANA dipolar interlayer shows a superior stability. After 45 d of storage under ambient conditions, the unencapsulated device preserved over 90% of its initial efficiency.