Effect of Cu content in CIGSe absorber on MoSe2 formation during post-selenization process

Abstract

MoSe2 layers, which would help to form ohmic contact and improve the adhesion, were formed at the Mo/CIGSe interface during the CIGSe preparing process. However, a thick MoSe2 layer could introduce carrier recombination center, high contact resistance, and might result in poor adhesion of CIGSe films, which played a deleterious role in the efficiency of the devices. In this study, the effect of Cu content and Ga diffusion on the formation of MoSe2 layer was investigated. The thick MoSe2 layer tended to form with Cu/(In + Ga) < 0.7, and MoSe2 was difficult to form at the Mo/CIGSe interface when Cu/(In + Ga) > 0.9. Finally, CIGSe thin film with large grains and a thin MoSe2 layer was obtained with the value of Cu/(In + Ga) between 0.8 and 0.9, and an 11.04% efficiency CIGSe solar cell was fabricated with the open circuit voltage of 505 mV.