Interface Modification by Ammonium Sulfamate for High-Efficiency and Stable Perovskite Solar Cells

Defects in perovskite films are still the dominant destroyer of both power conversion efficiency (PCE) and long-term stability in perovskite solar cells (PSCs). As the most popular electron transport layer (ETL), TiO2 film is used in many PSCs to achieve high PCE. However, pristine TiO2 by itself is not sufficient as an ETL due to lattice mismatch, poor alignment of the energy level gap, and hysteresis of the PSC. Herein, ammonium sulfamate (AS), with desired NH4+ and SO functional groups, is designed to modify the TiO2 surface and interface to improve the PCE of PSCs. It is found that the AS works like a seed layer for the perovskite deposition, and, in addition, it effectively forms a bridge between the TiO2 surface and the perovskite. As a result, PSCs are successfully fabricated with a champion power conversion efficiency of 24.78% with smaller hysteresis. The PSCs prepared using the AS-modified TiO2 also show excellent stability, and the bare device without any encapsulation retains 96% of its initial PCE after 1056 h of ambient exposure at 25 & DEG;C and 25% relative humidity. By introducing ammonium sulfamate between the TiO2 layer and the perovskite layer as an interface modification material, the energy level distribution of TiO2 is regulated, the interface defects are passivated, the electrical properties of TiO2 are improved, and the electron transport ability of TiO2 layer is promoted. Finally, high-efficiency and stable PSCs are prepared.image