SYNTHESIS OF OPTIMIZED CZTS THIN FILMS FOR PHOTOVOLTAIC ABSORBER LAYERS BY SPUTTERING FROM SULFIDE TARGETS AND SULFURIZATION

摘要

Cu_2ZnSnS_4 (CZTS) is a promising alternative for Cu(In,Ga)Se_2 (CIGS) absorber layers in thin film solar cells and is comprised of commodity elements which will enable scale-up of chalcopyrite panel production unhindered by elemental supplies and costs. Various CZTS synthesis methods, especially sulfurization of stacked metal or metal sulfide layers, are being studied and have led to cell efficiencies up to 6.7% [1]. Here we report our studies of CZTS thin film synthesis via room temperature co-sputtering from Cu_2S, ZnS and SnS_2 binary targets, followed by sulfurization between 500 °C - 650 °C using elemental sulfur vapor. Sputtering from sulfur-containing targets is designed to increase the sulfur content in the precursor films to promote stoichiometry. We report on the effects of processing including deposition on soda-lime and borosilicate glasses and deposition of Na-containing layers on film morphology, composition, phase, grain size, and electronic structure.