Cu 2 ZnSnS 4 polycrystalline thin films with large densely packed grains prepared by sol-gel method

Abstract

Cu2ZnSnS4 (CZTS) was obtained from a sol-gel precursor which consists of copper chloride, zinc chloride, tin chloride, and thiourea. CZTS thin films were prepd. by spin-coating the sol-gel precursor followed by annealing in a nitrogen atm. The morphol., compn., and structure of the absorber layer were studied by SEM, energy dispersive spectroscopy, X-ray diffraction, and Raman scattering. The optical measurement shows the bandgap of these films is .apprx.1.51 eV, and the optical absorption coeff. is on the order of 104 cm-1. CZTS solar cells with a structure of low-alkali glass/Mo/CZTS/CdS/i-ZnO/ZnO:Al/Al grid were tentatively fabricated. The best solar cell showed a short-circuit c.d. of 5.06 mA/cm2, an open-circuit voltage of 358 mV, a fill factor of 34.66%, and an efficiency of 0.63% under AM1.5 (100 mW/cm2) illumination. These results demonstrate the CZTS thin films were successfully deposited by a cheap sol-gel technique.