Light trapping in solar cells at the extreme coupling limit

TL;DR

This paper calculates the maximum possible light absorption enhancement in thin film solar cells through guided mode excitation, considering various physical factors, and provides tighter bounds for optimizing solar cell design.

Contribution

It introduces a comprehensive calculation of the extreme coupling limit for guided mode absorption enhancement in thin film solar cells, accounting for multiple physical parameters.

Findings

Tighter bounds for absorption enhancement are established.

Significant improvement in light trapping is theoretically possible.

Guided modes can be better exploited in thin film devices.

Abstract

We calculate the maximal absorption enhancement obtainable by guided mode excitation in a weakly absorbing dielectric slab over wide wavelength ranges. The slab mimics thin film silicon solar cells in the low absorption regime. We consider simultaneously wavelength-scale periodicity of the texture, small thickness of the film, modal properties of the guided waves and their confinement to the film. Also we investigate the effect of the incident angle on the absorption enhancement. Our calculations provide tighter bounds for the absorption enhancement but still significant improvement is possible. Our explanation of the absorption enhancement can help better exploitation of the guided modes in thin film devices.