Fabrication of Cu₂ZnSnS₄solar cells with 5.1% efficiency via thermal decomposition and reaction using a non-toxic sol–gel route

Abstract

Earth-abundant Cu2ZnSnS4 (CZTS) has been confirmed as a promising semiconductor material for thin film solar cells. To meet the requirements of high-efficiency and low-cost for photovoltaic technologies, a modified thermal decomposition sol–gel method with low-cost and low-toxicity for CZTS thin film preparation is presented, and the detailed formation mechanism of the thin film is investigated to obtain an optimized process. By introducing non-aqueous thiourea–metal–oxygen sol–gel processing, as well as applying extrinsic dopants and chemical etching, high-quality and phase-controlled CZTS thin films with homogeneous elemental distribution and a low impurity content have been synthesized. Based on the modified sol–gel method, solar cells with a structure of Ni:Al/ZAO/i-ZnO/CdS/CZTS/Mo/glass have been fabricated, and a power conversion efficiency of 5.10% is obtained, indicating its potential for high-throughput and high power conversion efficiency photovoltaic devices.