Effect of post-deposition annealing on the performance of D.C. sputtered Cu2SnSe3 thin films

Cost-effective Cu2SnSe3 thin films for the absorption layer of solar cells were prepared by D.C. sputtering. Different sputtering targets were fabricated by sintering the different mixtures of Cu2Se and SnSe2 powders. SnSe2 instead of commercially available SnSe was self-synthesized and used for thin-film solar cells for the first time. With our approach, Cu2SnSe3 thin films can be treated at higher temperatures for the benefit of larger grain size, which is an important factor for the performance of solar cells. The effects of target composition and annealing temperature on the properties of Cu2SnSe3 thin films were investigated. Structure, surface morphology, composition, and electrical and optical properties at different process conditions were measured. After 500 °C annealing, 400 °C-sputtered films can display with the direct band gap of 0.84 eV and has an electrical resistivity of ~ 0.18 Ω cm, absorption coefficient of 104–105 cm− 1, carrier concentration of ~ 1019 cm− 3, and electrical mobility of 3–10 cm2/V s.