New approaches to solar energy conversion using Si/liquid junctions

Abstract New data are presented on efficient Si/liquid junction photoelectrochemical energy conversion devices. Additional information on the interfacial energetics, charge transfer kinetics, and stabilization factors of these interfaces has been obtained using a variety of chemical and electrical methods. Transconductance and Mott-Schottky measurements of the barrier height of n-Si/CH 3 OH-Me 2 Fc +/0 contacts have demonstrated that the Si is in strong inversion, with a barrier height of 1.0 eV. Qualitative evidence for the validity of Marcus-Gerischer theory was obtained in measurements of the stabilization ratio as a function of the reorganization energy of the stabilizing redox agent. In addition, a new type of photoelectrochemical cell, in which charge carriers are collected primarily using diffusion gradients as opposed to drift, has shown high efficiency and unpinned electrical junction behavior in contact with various redox couples.