Multiple band and impurity photovoltaic solar cells: General theory and comparison to tandem cells

Abstract

One way to improve photovoltaic solar energy performance is to absorb photons by processes involving multiple energy thresholds, such as in tandem cells, that employ multiple solar cells of different semiconductor bandgaps. Recently, another multiple threshold approach has been analysed based on a single bandgap cell with an intermediate impurity band. In the present work, the approach is extended to the N-band cell, shown to be capable of higher performance than an N-cell tandem. A generic approach to obtaining the selective photon absorption required for high efficiency is also described and the resulting insights applied to a new analysis of the impurity photovoltaic effect. Copyright © 2001 John Wiley & Sons, Ltd.