Bifunctional Interface Engineering by Oxidating Layered TiSe2 for High-Performance CsPbBr3 Solar Cells

The electron transport layer (ETL) of TiO2 plays an important role in the field of perovskite solar cells (PSCs). However, low mobility, catalytic activity, and high trap defects after high-temperature sintering hinder the further improvement of PSCs. Herein, a twodimensional material (2D) of TiSe2 was introduced as the precursor material to fabricate TiO2 ETL by oxidating TiSe2 in air. The oxidized TiSe2 can fully convert into TiO2 and serve as an ETL in the PSCs. TiO2 originated from oxidized TiSe2 not only reduces the trap defects in ETL but also improves the energy level alignment between the ETL and the perovskite film. The optimized TiO2-TiSe2-based device shows a high performance of 9.31% as compared to 8.17% for conventional TiO2-based PSCs. On the basis of the TiO2/TiO2-TiSe2 ETL-based device, a champion efficiency of 10.16% was obtained. Furthermore, the unencapsulated devices exhibited outstanding stability in both thermal condition and humidity environment for more than 750 and 2000 h, respectively.