Two-step photon absorption carrier dynamics in hematite/silicon photoanode for Z-scheme water splitting

• First observation of two-step photon absorption dynamics in hematite/silicon photoanodes at room temperature. • Novel drift–diffusion simulation confirms carrier transport mechanisms in Z-scheme water splitting systems. • Insights provided for optimizing hematite/silicon photoelectrodes and advancing photovoltaic technologies. This study investigates the carrier dynamics of two-step photon absorption in a hematite/silicon (α-Fe 2 O 3 /Si) heterojunction photoanode for Z-scheme water splitting. Using liquid-phase deposition followed by annealing, we fabricated a photoanode capable of sequentially absorbing ultraviolet (UV) and infrared (IR) photons, achieving enhanced photocurrent densities in the mA/cm 2 range. For the first time, experimental characterization of two-step photon absorption carrier dynamics was combined with drift–diffusion simulations incorporating two-step photon absorption and recombination dynamics, providing robust theoretical validation. Our findings highlight the critical role of carrier recombination and transport at the α-Fe 2 O 3 /Si interface in achieving efficient Z-scheme systems. Meanwhile, this framework offers insights for developing advanced intermediate band and ratchet-type solar cells, where similar two-step photon absorption processes remain unachieved at room temperature.