Quantitative determination of optical and recombination losses in thin-film photovoltaic devices based on external quantum efficiency analysis

TL;DR

This paper introduces a comprehensive analysis method to quantitatively evaluate optical and recombination losses in various thin-film photovoltaic devices using external quantum efficiency spectra, enhancing understanding of loss mechanisms.

Contribution

The authors develop a general, systematic analysis scheme for assessing optical and recombination losses from EQE spectra applicable to diverse thin-film solar cells.

Findings

Effective separation of optical absorption and recombination losses.

High accuracy in fitting EQE spectra across different solar cell types.

Insights into parasitic absorption effects in photovoltaic devices.

Abstract

In developing photovoltaic devices with high efficiencies, quantitative determination of the carrier loss is crucial. In conventional solar-cell characterization techniques, however, photocurrent reduction originating from parasitic light absorption and carrier recombination within the light absorber cannot be assessed easily. Here, we develop a general analysis scheme in which the optical and recombination losses in submicron-textured solar cells are evaluated systematically from external quantum efficiency (EQE) spectra. In this method, the optical absorption in solar cells is first deduced by imposing the anti-reflection condition in the calculation of the absorptance spectrum, and the carrier extraction from the light absorber layer is then modeled by considering a carrier collection length from the absorber interface. Our analysis method is appropriate for a wide variety of photovoltaic devices, including kesterite solar cells [Cu2ZnSnSe4, Cu2ZnSnS4, and Cu2ZnSn(S,Se)4], zincblende CdTe solar cells, and hybrid perovskite (CH3NH3PbI3) solar cells, and provides excellent fitting to numerous EQE spectra reported earlier. Based on the results obtained from our EQE analyses, we discuss the effects of parasitic absorption and carrier recombination in different types of solar cells.