ULTRAFAST PHOTOINDUCED ELECTRON-TRANSFER ACROSS SEMICONDUCTOR LIQUID INTERFACES IN THE PRESENCE OF ELECTRIC-FIELDS

The rates of photoinduced electron transfer from p-InP to Fe(CN)64-/3- acceptors in aqueous electrolyte have been determined as a function o f the initial potential drop (i.e., band bending (V(BO)) in the semico nductor space charge layer using femtosecond luminescence up-conversio n techniques. The effects of electric field on electron transfer were separated from the effects of field-enhanced charge separation and sur face recombination through a rigorous numerical solution of the couple d continuity and Poisson equations using a Cray supercomputer. A very strong dependence of the electron-transfer velocity (S(et)) on V(BO) w as found, S(et) reached a saturation value of 5 X 10(7) cm/s when the initial value of V(BO) in the dark was greater-than-or-equal-to 0.5 eV . When the initial value of V(BO) was set near zero, S(et) was 9 X 10( 3) cm/s. Hot electron injection processes appear to play a role in thi s behavior.