Effect of RF sputter power on deposition of CZTX (X=S, Se) active layer without selenization/sulfurization, for solar cell applications

Copper Zinc Tin Selenide Cu2ZnSnSe4 (CZTSe) and Copper Zinc Tin Sulfide Cu2ZnSnS4 (CZTS) thin films were deposited from a multicomponent single target with different RF sputter powers and a constant annealing temperature of 450 degrees C. One step deposition with in-situ annealing was performed in order to avoid the individual metal losses during the process. Effects of various deposition parameters were investigated to finely control the elemental ratio of the quaternary target which in-turn helps to obtain the desired stoichiometry suitable for solar absorber materials as confirmed from EDS analysis. The phase purity of thin films was investigated and confirmed using XRD and Raman spectroscopy. A thin film solar cell device with n-CdS, ZnO, ZnO:Al layers and Al grids over the prepared kesterite CZTX (X = S, Se) films were deposited on Mo coated soda lime glass using complete vacuum deposition technique. Even though the optical, electrical and structural results are promising, the conversion efficiency for these single step processed CZTSe and CZTS solar cell devices were limited to 3.72% and 2.6% due to possible interface effect and smaller grain size of the deposited films. Considering the industrial fabrication of kesterite thin film solar cells, this processes assures an environmental friendly approach with inherent purity leading to one-step reduction in the mass production process. (C) 2021 Elsevier B.V. All rights reserved.