Numerical analysis and optimization of photovoltaic performance of Sb2Se3 based photocathode

Antimony selenide (Sb₂Se₃) based heterojunction photocathodes have recently received an increased attention, largely due to their outstanding performances for hydrogen production through photoelectrochemistry (PEC) water splitting. The PEC water splitting process encompasses both physical and electrochemical processes. The physical process is capable of generating a photo-voltage, which can drive the photo-generated electrons transport to the electrode/electrolyte interface through the p-n junction. However, unlike traditional photovoltaic device, the protective layer and co-catalyst will also affect the electrical performance of device, resulting in a decrease in PEC performances and stability. How to optimize the electrical properties of the photoelectrode is a concern. In this work, devoted to Sb₂Se₃/TiO₂ photocathode structures, the photovoltaic performances of a photocathode were modeled and analyzed from three aspects: p-n junction, back contact, and transition layer between TiO₂ and co-catalyst, using the SCAPS-1D software and a realistic set of material parameters. Based on reported optimization strategy, tthe interface electrical characteristics of photocathode were studied by adjusting energy band, donor/acceptor density, defect density, electron affinity, and other parameters. A low-cost and easy to implement optimization strategy was proposed, which used Cd_1-xZn_xS as the buffer layer between p-n junctions, W-doped TiO₂ as the transition between TiO₂/co-catalyst, and Sn-doped Sb₂Se₃ as the back surface layer to suppress the carrier recombination. The optimized photocathode can theoretically obtain photoelectric conversion efficiency of 17.01%–17.14% and a maximum J_sc of 38.79 mA/cm², exhibiting the potential to obtain a large photocurrent in the photoelectrochemical water splitting process.