Abstract
Long-term dry heating under light irradiation slightly reduces the conversion efficiency of CIGS solar cells. In contrast, Dark dry heating significantly decreases the conversion efficiency. The net acceptor concentration considerably decreases after dark heating, and the reduction of acceptors results in decreasing the open-circuit voltage and fill factor. After light soaking, the net acceptor concentration increases due to metastable acceptors in CIGS layers, and the open-circuit voltage and fill factor partly recover. Therefore, metastable acceptor concentrations should be controlled using light irradiation to evaluate correctly degradation rates using by accelerated lifetime test.
