Ab initio calculation of the detailed balance limit to the photovoltaic efficiency of single p-n junction kesterite solar cells

TL;DR

This paper introduces an ab initio method to accurately predict the maximum efficiency of single-junction kesterite solar cells by accounting for both radiative and non-radiative recombination processes, improving upon traditional thermodynamic limits.

Contribution

It presents a novel ab initio approach that incorporates defect-related non-radiative processes into efficiency calculations for thin-film solar cells.

Findings

Radiative efficiency limit at 2.6 micrometers film thickness

Efficiency gains are offset by increased recombination losses at optimal thickness

Method enables more accurate efficiency predictions considering defect effects

Abstract

The thermodynamic limit of photovoltaic efficiency for a single-junction solar cell can be readily predicted using the bandgap of the active light absorbing material. Such an approach overlooks the energy loss due to non-radiative electron-hole processes. We propose a practical ab initio procedure to determine the maximum efficiency of a thin-film solar cell that takes into account both radiative and non-radiative recombination. The required input includes the frequency-dependent optical absorption coefficient, as well as the capture cross-sections and equilibrium populations of point defects. For kesterite-structured Cu$_2$ZnSnS$_4$, the radiative limit is reached for a film thickness of around 2.6 micrometer, where the efficiency gain due to light absorption is counterbalanced by losses due to the increase in recombination current.