Impact of heat‐light soaking on potassium fluoride treated CIGS solar cells with CdS buffer layer

Abstract

AbstractIn this study, the effects of light‐soaking (LS), heat‐soaking (HS), and combined LS and HS, that is, heat‐light soaking (HLS) on potassium fluoride (KF)‐treated and KF‐free copper indium gallium selenide (CIGS) solar cells with CBD‐CdS buffer layer were investigated. LS and HS did not change the basic solar cell parameters of CIGS solar cells when they were performed separately. In contrast, HLS improved cell efficiency with increased open‐circuit‐voltage for KF‐treated CIGS solar cells, whereas it reduced cell performance for KF‐free CIGS cells. Capacitance‐voltage measurements confirmed a significantly increased carrier concentration in KF‐treated CIGS solar cells, as compared to KF‐free cells by HLS. X‐ray photoelectron spectroscopy measurement revealed that the HLS did not change the atomic concentration of Cd, S, and O in CBD‐CdS buffer layer. However, the concentration of Na atoms slightly increased at the CIGS surface region, as confirmed from SIMS measurement. It implies a possible reason for increased carrier concentration in KF‐treated CIGS solar cells after HLS. Temperature‐dependent current‐voltage measurements suggests that HLS modify a K‐containing new layer and affects cell performance.