Structure and optoelectrical properties of Cu-poor and Zn-rich CZTS films processed by the compaction of aqueous-synthesized nanoparticles

Cu-poor and Zn-rich Cu 2 ZnSnS 4 nanoparticles (NPs) with sizes between 5 and 10 nm and single kesterite phase were synthesized by a glycine-assisted aqueous solution process. Cu 2 ZnSnS 4 films were deposited on Mo foils by a process involving printing of NP-based inks by blade coating, hydraulic compaction, and annealing at 500 °C in Ar atmosphere. The analysis of crystalline structure confirmed that the resulting films had the kesterite- Cu 2 ZnSnS 4 phase. Moreover, the hydraulic compaction applied to the ink-coated substrates promoted the formation of crack-free films with enhanced crystallinity and reduced porosity. The optical band gap of these films was found in the range of 1.44 to 1.5 eV. Although there was a reduction in thickness from 4.14 to 1.44 µm with increasing hydraulic compaction from 500 to 800 MPa, the final Cu 2 ZnSnS 4 film exhibited an improvement in photoresponse evidenced by a moderate increase in current under both dark and lighting conditions related to a greater number of conductive grains in contact (due to increased film densification), creating more paths for electrons and thus reducing overall resistance.