Quantification of the Contact Resistance of ZnO/MoSe2/Mo Contact Formed in a Monolithic CIGS Photovoltaic Module

This study investigated the effect of MoSe2 on the contact resistance (RC) of the transparent conducting oxide (TCO) and Mo contact in the P2 region of the CIGS photovoltaic module. MoSe2 formed in the process of making the Cu(In,Ga)Se2 (CIGS) absorber layer imparts ohmic contact properties to the CIGS/Mo contact. In the process of connecting cells in series to fabricate a CIGS photovoltaic module, TCO/MoSe2/Mo contact was formed, and it was confirmed that MoSe2 increased the RC of this contact using the transmission line method. It is estimated that the reason MoSe2 increases the RC is due to conduction band offset (CBO). When ZnO used as TCO forms a contact with MoSe2, 0.6 eV CBO is formed due to the difference in electron affinity. This CBO can act as a resistor that impedes the flow of current. Therefore, in order to reduce the contact resistance of the CIGS solar module and increase the power conversion efficiency, it is necessary to make the MoSe2 thin enough to facilitate carrier tunneling.