Photoelectrode configuration as the key to the conversion efficiency of photoelectrochemical (PEC) water splitting system has attracted much attention. Here, for Si/α-Fe2O3 heterojunction photoanode, we present an optoelectronic study on the microscopic photoelectric processes inside the dual-absorbable photoanode and at the semiconductor/electrolyte interface. We systematically simulate the carrier generation, separation, recombination, and collection of the electron-hole pairs so that the complete optical and electrical responses of this kind of electronic devices can be obtained. The systems under consideration include n-Si/α-Fe2O3/electrolyte, p-Si/α-Fe2O3/electrolyte, and α-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 obtained and compared. The optoelectronic simulation and investigation provide a convenient methodology for the design of PEC-related systems for improved performance.
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