Hot-carrier transfer at photocatalytic silicon/platinum interfaces

Interfacial charge transfer from silicon to heterogeneous catalysts plays a key role in silicon-based photoelectrochemical systems. In general, prior to interfacial charge transfer, carriers that are generated by photons with energies above the bandgap dissipate the excess kinetic energy via hot-carrier cooling, and such energy loss limits the maximum power conversion efficiency. The excess energy of hot-carriers, however, could be utilized through hot-carrier transfer from silicon to the catalysts, but such hot-carrier extraction has not yet been demonstrated. Here, we exploit transient reflection spectroscopy to interrogate charge transfer at the interface between silicon and platinum. Quantitative modeling of the surface carrier kinetics indicates that the velocity of charge transfer from silicon to platinum exceeds 2.6 × 10⁷ cm s^-1, corresponding to an average carrier temperature of extracted carriers of ∼600 K, two times higher than the lattice temperature. The charge transfer velocity can be controllably reduced by inserting silica spacing layers between silicon and platinum.