Modelling Multi Quantum Well Solar Cell Efficiency

TL;DR

This paper extends a quantum well solar cell efficiency model to multi-quantum well systems, incorporating dark current theory and Shockley-Read-Hall recombination, to evaluate and predict high efficiency potential.

Contribution

It introduces a methodology for modeling multi-quantum well solar cells based on dark current theory and SRH recombination, extending previous single-well models.

Findings

Dark currents in MQW systems require reduced quasi Fermi level separation.

Model aligns well with experimental data across different materials.

High efficiency potential indicated for optimized MQW solar cells.

Abstract

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.