Effect of the quantum well thickness on the performance of InGaN photovoltaic cells

TL;DR

This study investigates how varying the quantum well thickness in InGaN/GaN solar cells affects their band gap and efficiency, revealing a trade-off between redshift benefits and defect-induced performance degradation.

Contribution

It provides new insights into the relationship between quantum well thickness, optical properties, and performance limitations in InGaN-based photovoltaic cells.

Findings

Redshift of band-to-band transition from 395 to 474 nm with increased well thickness

Absorption edge shift is less pronounced in thicker wells due to higher energy transitions

Thicker wells induce defects from strain relaxation, reducing cell efficiency

Abstract

We report on the influence of the quantum well thickness on the effective band gap and conversion efficiency of In0.12Ga0.88N/GaN multiple quantum well solar cells. The band-to-band transition can be redshifted from 395 to 474 nm by increasing the well thickness from 1.3 to 5.4 nm, as demonstrated by cathodoluminescence measurements. However, the redshift of the absorption edge is much less pronounced in absorption: in thicker wells, transitions to higher energy levels dominate. Besides, partial strain relaxation in thicker wells leads to the formation of defects, hence degrading the overall solar cell performance.