Kesterite Cu2ZnSnS4 thin film solar cells by a facile DMF-based solution coating process†
Abstract
Kesterite Cu2ZnSnS4 (CZTS) thin films were fabricated using a low-cost and environmentally friendly route from a dimethylformamide (DMF) solution of a metal–thiourea complex. Thermal gravimetric analysis (TGA) has been performed to reveal the thermal decomposition behavior of the CZTS precursors for drying and sulfurization process design. A facile solution method of in situ introducing sodium dopant by adding NaOH into the precursor solution is presented. The sodium dopant improves the open circuit voltage (Voc) and fill factor (FF) and thereby enhances the power conversion efficiency from 4.47% to 5.68%. The enhanced performance is related to the increased grain size and increased minority carrier lifetime. A large number of large voids observed in the bulk absorber and at the absorber/back contact interface are considered to be the main reason for the low short circuit current density (Jsc).