Improved efficiency of Cu(In,Ga)Se2 thin film solar cells by surface sulfurization using wet process

Surface sulfurization of CIGS thin films was carried out using aqueous solutions with group III chlorides (III=In, Ga, Al, Y) and thioacetamide (CH₃CSNH₂) in order to improve the junction characteristics of CIGS-based solar cells. All of the basic cell parameters of the CIGS-based thin film solar cells were found to improve dramatically after these treatments. In particular, the J_sc value increased remarkably for all devices with Ga-S and Al-S treatments. XPS analysis suggests that the origin of improved cell performance can be attributed to the formation of very thin sulfide layer on the CIGS layer and/or surface passivation by S atoms.