Carrier loss mechanisms in textured crystalline Si-based solar cells

TL;DR

This paper introduces a simple, low-cost method to analyze optical and recombination losses in crystalline silicon solar cells, revealing limiting factors in high-efficiency devices and enabling detailed carrier loss mechanism insights.

Contribution

A novel EQE-based analysis technique that accurately characterizes carrier loss mechanisms in textured crystalline silicon solar cells without complex fitting.

Findings

The method fits EQE spectra of various textured c-Si solar cells with high accuracy.

It enables extraction of minority carrier diffusion length and surface recombination velocity.

Carrier loss mechanisms vary across different c-Si solar cell types.

Abstract

A quite general device analysis method that allows the direct evaluation of optical and recombination losses in crystalline silicon (c-Si)-based solar cells has been developed. By applying this technique, the optical and physical limiting factors of the state-of-the-art solar cells with ~20% efficiencies have been revealed. In the established method, the carrier loss mechanisms are characterized from the external quantum efficiency (EQE) analysis with very low computational cost. In particular, the EQE analyses of textured c-Si solar cells are implemented by employing the experimental reflectance spectra obtained directly from the actual devices while using flat optical models without any fitting parameters. We find that the developed method provides almost perfect fitting to EQE spectra reported for various textured c-Si solar cells, including c-Si heterojunction solar cells, a dopant-free c-Si solar cell with a MoOx layer, and an n-type passivated emitter with rear locally diffused (PERL) solar cell. The modeling of the recombination loss further allows the extraction of the minority carrier diffusion length and surface recombination velocity from the EQE analysis. Based on the EQE analysis results, the carrier loss mechanisms in different types of c-Si solar cells are discussed.