Optoelectronic modeling of the Si/alpha-Fe2O3 heterojunction photoanode

In photoelectrochemical (PEC) water-splitting systems, photoelectrode configuration is a key ingredient to obtain the high conversion efficiency. To effectively guide the device fabrication, the intrinsic multi-domain physics and mechanisms (e.g., light absorption in optical domain and carrier generation/separation/transport/collection in electrical domain) have to be uncovered, which requires the advanced optoelectronic simulation. In this study, focusing on the Si/alpha-Fe2O3 heterojunction photoanodes, we present a comprehensive optoelectronic study on the microscopic photoelectric processes inside the dual-absorbable photoanode. We systematically simulate the carrier generation, separation, recombination, and collection of the electron-hole pairs so that the complete optoelectronic responses of this kind of electronic devices can be obtained. The systems under consideration include n-Si/alpha-Fe2O3/electrolyte, p-Si/alpha-Fe2O3/electrolyte, and alpha-Fe2O3/electrolyte systems in order to uncover the intrinsic physics as well as find the optimal device designs. We obtain the spectra of light absorption, output-and recombination-photocurrent profiles, along with the current-voltage characteristics under dark and illumination conditions. Moreover, the energy band diagram under various system configurations are calculated and compared. The optoelectronic simulation and investigation provide a convenient methodology for the design of PEC-related systems for improved performance.