Stability of Unpackaged CIGS Solar Cells under Illumination with Damp Heat, Dry Heat and Dry Cold followed by Cycling

Unpackaged CIGS solar cells were simultaneously exposed to illumination and either dry heat, damp heat or dry cold followed by thermal cycling. In-situ monitoring of their electrical parameters demonstrated a rapid decrease of the efficiency for the solar cells exposed to damp heat plus illumination. This decrease was mainly driven by changes in the shunt resistances, affecting also the open circuit voltage and the fill factor, while a minor increase in series resistance was also observed. All solar cells exposed to dry heat plus illumination were quite stable during the exposure in both their electrical and material parameters. The dry cold/cycling solar cells similarly barely showed any degradation, although one sample became shunted, likely due to structural changes in the solar cell. From these experiments, it was concluded that unpackaged CIGS solar cells can degrade rapidly in the presence of humidity, but in the absence of water, these solar cells were mostly stable. This indicates that these unpackaged CIGS solar cells can majorly stand combined illumination, and the accompanying electrical field, and various temperatures.