Enhancing the Performance of Carbon‐Based All‐Inorganic CsPbIBr2 Perovskite Solar Cells via Na2SiO3 Surface Treatment for Passivation of the TiO2/Perovskite Interface

Abstract

CsPbIBr2 has garnered significant interest due to its ideal bandgap and good stability. However, defects formed at the interface between the electron transport layer and the perovskite can lead to increased non‐radiative recombination, which negatively impacts both the power conversion efficiency (PCE) of perovskite solar cells and the long‐term stability of the cells. Herein, the TiO2/perovskite interface is modified by adding sodium silicate to passivate the defects on the interface. The introduction of Na+ partially reduces Ti4+ to Ti3+ in TiO2, thereby passivating trap states caused by oxygen vacancy defects and adjusting the energy level alignment between TiO2 and the perovskite film, enhancing the carrier transport efficiency. Additionally, SiO32− can form SiOPb (and Cs) bonds with the undercoordinated Pb2+ and Cs+ on the surface of the perovskite layer, effectively passivating surface defects of the perovskite film and thereby improving the efficiency of the devices. Ultimately, the carbon‐based all‐inorganic CsPbIBr2 perovskite solar cells treated with Na2SiO3 exhibit a significantly improved PCE of 10.85% compared to 8.62% of the control sample and achieve a high open‐circuit voltage of 1.31 V. With this modification, the devices also demonstrate reduced hysteresis effects and enhanced stability.