  The spectral response of quantum well solar cells (QWSCs) is well understood.
We describe work on QWSC dark current theory which combined with SR theory
yields a system efficiency. A methodology published for single quantum well
(SQW) systems is extended to MQW systems in the Al(x) Ga(1-x) As and
InGa(0.53x) As(x) P systems. The materials considered are dominated by
Shockley-Read-Hall (SRH) recombination. The SRH formalism expresses the dark
current in terms of carrier recombination through mid-gap traps. The SRH
recombination rate depends on the electron and hole densities of states (DOS)
in the barriers and wells, which are well known, and of carrier non-radiative
lifetimes. These material quality dependent lifetimes are extracted from
analysis of suitable bulk control samples. Consistency over a range of AlGaAs
controls and QWSCs is examined, and the model is applied to QWSCs in InGaAsP on
InP substrates. We find that the dark currents of MQW systems require a
reduction of the quasi Fermi level separation between carrier populations in
the wells relative to barrier material, in line with previous studies.
Consequences for QWSCs are considered suggesting a high efficiency potential.
