BEHAVIOR OF SI PHOTOELECTRODES UNDER HIGH LEVEL INJECTION CONDITIONS. 3. TRANSIENT AND STEADY-STATE MEASUREMENTS OF THE QUASI-FERMI LEVELS AT SI/CH3OH CONTACTS

Real-time measurements of the photovoltage rise and decay at the back of lightly doped, thin, long lifetime Si photoelectrodes were recorded subsequent to a variety of spatial and temporal carrier generation impulses. The functional form of the rising portion of the photovoltage signal is sensitive to charge transport processes, and this signal was used to validate experimentally the hypothesis that charge transport in these samples under high level injection is primarily driven by diffusion, as opposed to drift. The decay of the photovoltage signal back to its equilibrium value yielded information concerning the surface recombination velocity, Sf, of the various Si/CH3OH redox couple contacts. These data validated the relatively high surface quality of the Si/liquid interface in contact with a variety of redox species. Furthermore, the low surface recombination velocities are in agreement with prior theoretical and experimental estimates of interfacial charge-transfer rate constants for semiconductors in...