Analytical Models of Bulk and Quantum Well Solar Cells and Relevance of the Radiative Limit

TL;DR

This paper reviews analytical models of bulk and quantum well solar cells, highlighting their dominant recombination mechanisms, the radiative limit in quantum wells, and implications for device efficiency and design.

Contribution

It introduces an analytical approach to estimate recombination mechanisms and demonstrates quantum well cells operate near the radiative limit, informing design strategies.

Findings

Bulk PIN cells are dominated by non-radiative recombination.

Quantum well PIN cells operate in the radiative limit.

Light trapping enhances photon recycling and reduces radiative losses.

Abstract

The analytical modelling of bulk and quantum well solar cells is reviewed. The analytical approach allows explicit estimates of dominant generation and recombination mechanisms at work in charge neutral and space charge layers of the cells. Consistency of the analysis of cell characteristics in the light and in the dark leaves a single free parameter, which is the mean Shockley-Read-Hall lifetime. Bulk PIN cells are shown to be inherently dominated by non-radiative recombination as a result of the doping related non-radiative fraction of the Shockley injection currents. Quantum well PIN solar cells on the other hand are shown to operate in the radiative limit as a result of the dominance of radiative recombination in the space charge region. These features are exploited using light trapping techniques leading to photon recycling and reduced radiative recombination. The conclusion is that the mirror backed quantum well solar cell device features open circuit voltages determined mainly by the higher bandgap neutral layers, with an absorption threshold determined by the lower gap quantum well superlattice.