METASTABLE CURRENT-VOLTAGE CHARACTERISTICS OF CU (IN, GA) SE_2 SOLAR CELLS AND ENERGY BAND ALIGNMENTS

摘要

The metastable current-voltage characteristics on Cu(In,Ga)Se_2 (CIGS) solar cells with controlled conduction band offset (CBO) values of window/CIGS layers were investigated. The CBO value was controlled by changing the band gap of a (Zn,Mg)O (ZMO) window layer. The metastable behaviors were observed in the CIGS solar cells when the conduction band of ZMO is higher than that of CIGS. The metastability becomes severe with increasing the CBO value. The quantum efficiency measurement revealed that the metastability in current-voltage curves were due to the metastable change of the photocurrent collection. The model of the metastability is discussed with simulated energy band diagrams.