Improved charge extraction through interface engineering for 10.12% efficiency and stable CsPbBr3 perovskite solar cells

Abstract

The favorable contact and matching energy level at the electrode/perovskite interface as well as the high-quality perovskite film are prerequisites for high photovoltaic performance perovskite solar cells (PSCs). Herein, an innovative interface engineering strategy has been proposed to modify TiO₂ as well as the perovskite film simultaneously by introducing ammonium chloride (AC), which not only improves the contact and energy level matching at the TiO₂/perovskite interface but also provides a high-quality perovskite film with larger grain size by regulating the crystallization kinetics of CsPbBr₃. Furthermore, chlorine anions in AC tend to combine with TiO₂ to passivate its surface defects; the ammonium cation can bond with the uncoordinated ionic defects of perovskite. As a result, a remarkably enhanced charge extraction and retarded charge recombination within inorganic CsPbBr₃ PSCs is acquired through the interface engineering of AC, and the power conversion efficiency of the modified device is increased from the original 6.59% to 9.60%. By compensating the energy level at the perovskite/carbon interface by setting an efficient hole-transporting layer of zinc phthalocyanine (ZnPc), the best efficiency up to 10.12% was achieved for the device with AC and ZnPc interface modification, which is much higher than 7.87% efficiency for the ZnPc-only PSCs, further demonstrating the important positive effects of AC modification on device performance. Moreover, the optimized device without any encapsulation presents an exceptional long-term stability under persistent attack by 80% RH air atmosphere at 25 °C for 720 h.