摘要
Metastable behavior of cesium fluoride (CsF)-treated Cu(In 1–x ,Ga x )Se 2 (CIGS) solar cells is investigated under heat-light soaking (HLS) and heat-soaking (HS) treatments. HLS increases open-circuit voltage, fill factor, efficiency, and net carrier concentration and decreases short-circuit current density, whereas heat-soaking treatment acts oppositely. The performance of a CsF postdeposition treatment to CIGS thin film in selenium vapor, and closer to stoichiometry copper content, did not mitigate the open-circuit voltage improvement after HLS. These results argue the traditional concept of the V Se –V Cu divacancy complex for the total beneficial effect of HLS in alkali-treated CIGS solar cells. The metastable behavior observed in the CsF-treated devices due to the HLS and HS treatments is explained by the specific behavior of alkali-containing new compounds at the surface and/or the migration of alkali metals at the surface and bulk regions.