Kinetics of Electron Transfer from Photoexcited Superlattice Electrodes

A kinetic model has been developed that quantitatively describes electron transfer from photoexcited superlattice electrodes into liquid solutions. The model permits electron transfer from all quantum levels as well as from surface states; it also takes into account recombination in the bulk, space charge layer, and surface states, and band-edge movement. The model calculations define the values of the rate constants for heterogeneous electron transfer and hot electron thermalization among the various energy levels in the superlattice quantum wells that are necessary to achieve hot electron transfer from excited quantum states. The question of whether hot electron transfer is manifested by a dependence of the photocurrent action spectra on acceptor redox potential is examined in detail.