Modeling of V graded In(x)Ga(1-x)N solar cells: comparison of strained and relaxed features

TL;DR

This study models V graded InGaN solar cells, comparing strained and relaxed conditions, revealing that relaxed structures can achieve higher efficiency, with a maximum of 8.3% at 90% indium composition.

Contribution

It introduces a detailed comparison of strained and relaxed InGaN solar cells using empirical and theoretical models, highlighting the impact of strain on efficiency.

Findings

Maximum efficiency of 5.5% under fully strained conditions at x=60%.

Maximum efficiency of 8.3% under relaxed conditions at x=90%.

Empirical Vegard-like law improves bandgap prediction for strained InGaN.

Abstract

The optical properties of V graded InGaN solar cells are studied. Graded InGaN well structures with the indium composition increasing then decreasing in a V shaped pattern have been designed. Through polarization doping, this naturally creates alternating p-type and n-type regions. Separate structures are designed by varying the indium alloy profile from GaN to maximum indium concentrations ranging from 20% to 80%, while maintaining a constant overall structure thicknesses of 100 nm. The solar cell parameters under fully strained and relaxed conditions are considered. The results show that a maximum efficiency of 5.5%, under fully strained condition occurs at x=60%. Solar cell efficiency under relaxed conditions increases to a maximum of 8.3% at 90%. While Vegards law predicts the bandgap under relaxed conditions, a Vegard like law is empirically determined from the output of Nextnano for varying In compositions in order to calculate solar cell parameters under strain.