Deep DFT Insights into Interface Engineering Based on 2G-WSe2 Buffer Layer for CsPbF3 Perovskite Solar Cells

Abstract

The buffer layer built in perovskite solar cells (PSCs) can effectively solve the problem of energy-level mismatch between adjacent functional layers, inhibit the degradation of perovskite layer by H2O and impurities, confirmed as a reliable strategy to improve the stability of PSCs. In this work, 2H-WSe2 with excellent optical properties and tunable bandgap was adopted as buffer layer to explore its effect on the interface structure and properties of CsPbF3 perovskite based on density functional theory (DFT). The monolayer WSe2 (001) is applied to the surface of CsPbF3 (001) by van der Waals forces to construct an expected type-II band structure. The electronic configuration induced by the interfacial polarization field and energy-level splitting of the W-d state leads to a more stable structure. The considerable potential barrier (> 1.6 eV) of the CsPbF3/WSe2 interfaces can efficiently prevent electron-hole recombination and facilitate carriers transfer. At 381 nm wavelength, the light absorption coefficient (α) of CsPbF3/WSe2 is 1.8 times higher than that of CsPbF3; and at the near-infrared end, the α of heterojunction is more than twice that of pure perovskite. According to the simulation of Solar Design, PSCs based on CsPbF3/WSe2 achieved power conversion efficiencies of 11.801%. This work reveals the mechanism of the effect on CsPbF3 provided by WSe2, such as improving the optical properties, interfacial stability and so on; more importantly, provides a feasible pathway for designing efficient and stable PSCs.

Keywords: Interfacial engineering, Crystal field splitting, 2H-WSe2/CsPbF3, DFT calculation, PSCs Device simulation