In Ambient Air Processed Cu2ZnSnS4 Absorber Layers from DMSO-Based Precursors: Enhanced Efficiency via Device Post-annealing

Solution-based processes have gained considerable attention as promising route toward high-efficiency kesterite-based photovoltaics. Dimethyl sulfoxide (DMSO) is commonly utilized as a solvent because of its low toxicity and exceptional solvating power, attributed to its high polarity, high dielectric constant, and strong Lewis base. However, most DMSO-based kesterite syntheses are conducted in glove boxes under inert gas atmosphere, increasing complexity and cost. In this work, we present precursor engineering strategies and simple post-annealing of device approach for fabricating high-performance Cu2ZnSnS4 (CZTS) solar cells using DMSO under ambient air. Four distinct precursor formulations were investigated, and a tailored post-annealing treatment was developed for the complete device to enhance the fill factor (FF) and overall power conversion efficiency (PCE). Post-annealing at 300 °C for 12 minutes in ambient air significantly enhanced device performance, yielding a PCE of 9.4% and increasing the FF from 33.0% to 62.0%. Comprehensive structural and optoelectronic characterization revealed improved heterojunction formation after the post-annealing. To the best of our knowledge, this represents the highest reported efficiency for CZTS solar cells without any alloying fabricated using DMSO under ambient air conditions. These findings demonstrate a cost-effective and scalable fabrication route and highlight the crucial role of device post-annealing in achieving high-efficiency air-processed CZTS solar cells.