Characterization of 19.9%-efficient CIGS absorbers

We recently reported a new record total-area efficiency, 19.9%, for CuInGaSe2 (CIGS)-based thin-film solar cells [1]. Current-voltage analysis indicates that improved performance in the record device is due to reduced recombination. The reduced recombination was achieved by terminating the processing with a Ga-poor (In-rich) layer, which has led to a number of devices exceeding the prior (19.5%) efficiency record. This paper documents the properties of the high-efficiency CIGS by a variety of characterization techniques, with an emphasis on identifying near-surface properties associated with the modified processing.