Multiple Bandgap Photoelectrochemistry: Energetic Configurations for Solar Energy Conversion

Abstract

The limiting constraints of multiple bandgap photoelectrochemical energy conversion are explored, as well as practical configurations for efficient solar to electrical energy conversion. Photoelectrochemical charge transfer is both electronic, and ionic, via electrochemical oxidation/reduction, which provides the basis for composite semiconductor/electrolyte systems which can convert and/or store solar energy. Multiple semiconductor bandgaps can enhance the energetics of this interaction. Twelve distinct multiple bandgap photoelectrochemical solar to electrical configurations are introduced, each with advantages and disadvantages. Successive multiple bandgaps may be arranged in either a bipolar or inverted order, and the latter can diminish the photopotential applied to the electrolyte. Both inverted or bipolar configurations can contain either a Schottky or ohmic photoelectrochemical solution interface, and each configuration can be either regenerative, generating external electrical work in which no net change in electrolyte composition occurs, or a storage cell, in which separate redox reactions are driven. ©1998 The Electrochemical Society