Proposal of CIGS dual-junction solar cell and investigation of different metal grids effect

Abstract

In this report, four different metallic grid connectivity models, namely graphene, aluminum, gold, and silver for the copper gallium diselenide/copper indium gallium diselenide (CGS/CIGS) dual-junction solar cell, are discussed. In this structure, it is assumed that the metal contact with the aluminum-doped zinc oxide (ZnO:Al) layer forms an ohmic contact. This assumption is true since the metal grids are sandwiched. The sandwich metal grid is such that at first a metal layer having an ohmic contact with ZnO:Al is deposited, then the desired metal layer is placed on the metal layer as contact. In fact, this metal grid replaces the transparent conductor oxide (TCO) in the structure. Using a metal grid instead of a TCO will increase the transparency and thus be more absorbent, because the TCO also has some absorption and does not allow much light to enter the absorber layer. Based on the results of the simulation and comparison of the performance of the metal patterns, we conclude that by choosing the graphene ohmic contact, we will achieve higher efficiency and absorption. The CIGS dual-junction solar cell features were obtained by graphene metal grid, short circuit current of 14.7403 mA/cm2, open circuit voltage of 1.99054 V, fill factor of 38.78%, and efficiency of 11.38%.