Enhancing solar cell efficiency of AlxIn1-xN/Si heterojunctions using an a-Si buffer: A study of material, interface and device properties

TL;DR

This paper demonstrates that an optimized amorphous silicon buffer layer enhances the structural quality and efficiency of AlInN/Si heterojunction solar cells, with optimal performance at specific aluminum content levels.

Contribution

It introduces a novel RF-sputtered a-Si buffer layer that improves AlInN/Si heterojunction solar cell efficiency and analyzes the impact of aluminum content on device performance.

Findings

Efficiency increased from 3.3% to 3.9% with the buffer.

Best performance at 22% Al content with 4.1% efficiency.

Performance declines above 36% Al due to resistivity and carrier issues.

Abstract

This study explores the impact of an optimized amorphous silicon (a-Si) buffer layer on AlxIn1-xN-on-Si(100) heterojunction solar cells, with Al content varying from 0% (InN) to 55%. The buffer layer improves the structural quality of the AlInN layer, as evidenced by reduced full width at half maximum values in X-ray diffraction rocking curves around the AlInN (0002) peak. Atomic force microscopy reveals that the buffer layer does not alter surface roughness. The effectiveness of the a-Si buffer is demonstrated by an enhancement of the conversion efficiency under AM1.5G illumination from 3.3 % to 3.9 % for devices with 35 % Al. Looking at the effect of the Al content in devices with the a-Si buffer, the device with 22% Al shows the best photovoltaic performance, with a conversion efficiency of 4.1 % and a VOC of 0.42 V, JSC of 15.4 mA/cm2, and FF of 63.3%. However, performance declines for Al contents above 36% due to increased resistivity and reduced carrier concentration. These findings highlight the critical role of the novel a-Si buffer layer developed by RF-sputtering and the Al content in optimizing AlInN/Si heterojunction solar cell performance.