Device and performance parameters of Cu(In,Ga)(Se,S)2-based solar cells with varying i-ZnO layer thickness

Abstract

Abstract In pursuit of low-cost and highly efficient thin film solar cells, Cu(In,Ga)(Se,S) 2 /CdS/ i -ZnO/ZnO:Al (CIGSS) solar cells were fabricated using a two-step process. The thickness of i -ZnO layer was varied from 0 to 454 nm. The current density–voltage ( J – V ) characteristics of the devices were measured, and the device and performance parameters of the solar cells were obtained from the J – V curves to analyze the effect of varying i -ZnO layer thickness. The device parameters were determined using a parameter extraction method that utilized particle swarm optimization. The method is a curve-fitting routine that employed the two-diode model. The J – V curves of the solar cells were fitted with the model and the parameters were determined. Results show that as the thickness of i -ZnO was increased, the average efficiency and the fill factor ( FF ) of the solar cells increase. Device parameters reveal that although the series resistance increased with thicker i -ZnO layer, the solar cells absorbed more photons resulting in higher short-circuit current density ( J sc ) and, consequently, higher photo-generated current density ( J L ). For solar cells with 303–454 nm-thick i -ZnO layer, the best devices achieved efficiency between 15.24% and 15.73% and the fill factor varied between 0.65 and 0.67.