A solvothermal route to synthesize kesterite Cu2ZnSnS4 nanocrystals for solution-processed solar cells

•The high quality CZTS nanocrystals was obtained via solvothermal procedure.•The optical bandgap and energy levels of the CZTS nanocrystals was determined.•Influences of S concentration and Sn precursors on final products was analyzed.•CZTS nanocrystals based layers solar cell were fabricated by solution-processed.•1, 2-ethanedithiol were used for the solid-state ligand exchange.

Cu2ZnSnS4 (CZTS) has been proposed as an alternative earth-abundant absorber material for thin film solar cells. In this paper, we report a facile solvothermal method to produce impure-free kesterite CZTS nanocrystals. Optical band gap of the obtained high quality CZTS nanocrystals is 1.52 eV determined by UV–VIS–NIR absorption spectrum, which is match well with the optimum for photovoltaic solar conversion in a single-band-gap device. We closely systematically investigated both the concentration of Sulfur (S) and the species of precursor Tin (Sn) and their impact on the final products. Furthermore, CZTS nanocrystals based layers hybrid junction solar cells were fabricated by a layer-by-layer dip-coating method. The enhancement in photovoltaic performance was also explore through the solid state ligand exchange which was used 1, 2-ethanedithiol (EDT) to treat the CZTS nanocrystals layer. We achieved the best power conversion efficiencies (PCE) of 1.73% fabricated with the EDT treated CZTS nanocrystals layer, which is approximately 5 fold than the comparative devices without treatment.