# High efficiency wide gap Cu(In,Ga)Se2 solar cells: Influence of buffer layer characteristics

## TL;DR

This paper explores how buffer layer properties affect the efficiency of wide-gap CIGS solar cells.

## Contribution

The study identifies optimal buffer layer thickness and doping concentration for enhancing wide-gap CIGS solar cell performance.

## Key findings

- Lower CdS thickness improves efficiency when doping is low or similar to CGS layer.
- Higher CdS thickness improves efficiency when doping exceeds CGS layer.
- Optimal CdS thickness is around 50 nm with higher doping concentration.

## Abstract

Wide-gap Cu(In,Ga)Se2 (CIGS) solar cells exhibit a superior match to the solar spectrum, resulting in a higher ideal efficiency (Eff). However, in reality, their device Eff is lower than that of narrow-gap CIGS solar cells. This study aims to identify the factors that limit the performance enhancement of wide-gap CIGS solar cells, focusing on the characteristics of the buffer layer. The influence of the thickness and doping concentration of the CdS layer on the built-in electric field and interfacial recombination of the heterojunction has been investigated through simulation. The simulation results indicate that when the doping concentration of the CdS layer is lower than or similar to that of the CGS layer, decreasing the thickness of the CdS layer (e.g., 10 nm) is beneficial for improving device performance. However, if it is higher than that of the CGS layer, increasing the thickness of the CdS layer (e.g., 50 nm) is conducive to improving device performance. The thickness of the CdS layer that maximizes the Eff of the wide-gap CGS device should be approximately 50 nm, and its doping concentration should be higher than that of the CGS layer. This optimization can simultaneously enhance the built-in electric field of the heterojunction and minimize its interfacial recombination, thereby improving the open-circuit voltage and Eff of wide-gap CGS devices.

•Buffer properties impact built-in electric field and recombination in CGS solar cells.•Lowering CdS thickness boosts η when doping content is low or similar to CGS layer's.•Increasing CdS thickness boosts η when doping content surpasses the CGS layer's level.

Buffer properties impact built-in electric field and recombination in CGS solar cells.

Lowering CdS thickness boosts η when doping content is low or similar to CGS layer's.

Increasing CdS thickness boosts η when doping content surpasses the CGS layer's level.