  The quantum well solar cell (QWSC) has been proposed as a route to higher
efficiency than that attainable by homojunction devices. Previous studies have
established that carriers escape the quantum wells with high efficiency in
forward bias and contribute to the photocurrent. Progress in resolving the
efficiency limits of these cells has been dogged by the lack of a theoretical
model reproducing both the enhanced carrier gen- eration and enhanced
recombination due to the quantum wells. Here we present a model which
calculates the incremental generation and recombination due to the QWs and is
verified by modelling the experimental light and dark current-voltage
characteristics of a range of III-V quantum well structures. We find that
predicted dark currents are significantly greater than experiment if we use
lifetimes derived from homostructure devices. Successful simulation of light
and dark currents can be obtained only by introducing a parameter which
represents a reduction in the quasi-Fermi level separation.
