The role of the intrinsic zinc oxide layers on the performance of wide-bandgap (AgCu)(InGa)Se2 thin-film solar cells

Fundamental optoelectronic characterization of thin film (AgCu)(InGa)Se₂ solar cell structures to investigate the role of the high resistance (HR) ZnO is presented. Experiments were conducted varying the thickness and the resistivity of the HR ZnO. Deposited films and fabricated devices were characterized by a number of techniques including current-voltage and quantum efficiency. It was found that thickness between 10-100 nm had negligible impact on device performance but reducing the thickness to 0 nm resulted in huge variability in all device parameters. There was a weak improvement in all solar cell parameters with increasing the HR layer resistivity by 3 orders of magnitude from 4×10^-3 to 1×10¹ Ω-cm. This is due to reduced free carrier absorption (J_sc) and reduced lateral spread of the impact of local inhomogeneity and shunts (V_oc and FF).