Fabrication of Cu2ZnSnS4 screen printed layers for solar cells

Cu2ZnSnS4 layers have been successfully fabricated on flexible polyimide substrates by screen printing. The microparticles of Cu2ZnSnS4, which is the main raw material for preparing screen printing paste, were prepared by wet ball milling and sintering methods. X-ray diffraction characterization results show the screen printed Cu2ZnSnS4 layers were well indexed to single phase Cu2ZnSnS4. Scanning electronic microscopy images show the diameters and lengths of the as-prepared Cu2ZnSnS4 microparticles are about 30–50 and 150–200 nm, respectively. The bandgap, sheet resistance, carrier concentration, and Hall mobility of the screen printed Cu2ZnSnS4 layers were about 1.49 eV, 2.42×103 Ω, 3.81×1018 cm−3, and 12.61 cm2 V−1 s−s at 25 °C, respectively. To evaluate the photoresponse of the screen printed Cu2ZnSnS4 layers, complete photovoltaic cells with the structure of polyimide/Mo/Cu2ZnSnS4/CdS/ZnO:Al/Al-grid were further fabricated. The short-circuit current density, open-circuit voltage, fill factor, and efficiency of a typical photovoltaic cell with an active area of 0.15 cm2 were 4.76 mA/cm2, 386 mV, 0.27, and 0.49%, respectively.