Quaternary Cu2ZnSnS4 nanocrystals: Facile and low cost synthesis by microwave-assisted solution method

Cu2ZnSnS4 (CZTS) nanocrystals (NCs), a promising alternative for In- and Ga-free absorber materials, were snythesized by a novel route using a two-step process. In the first step, the precursor powders were obtained by microwave irradiation at 700 W for 10 min from aqueous solutions containing copper, zinc, tin and sulfur elements. In the second step, the precursor powder was sulfurized by annealing in H2S (5%) + N-2 (95%) atmosphere at 550 degrees C for 1 h. The structural, compositional, thermal and optical characteristics of CZTS NCs have been investigated. X-ray diffraction patterns, X-ray photoelectron spectroscopy and transmission electron microscopy results showed that the sulfurized NCs were a single kieserite CZTS phase without Cu2SnS3, ZnS, CuS and SnS secondary phases. Thermo-gravimetric analysis and differential-thermal analysis indicated a weight loss at about 840 degrees C and endothermic peak at same temperature from CZTS nature. Energy dispersive X-ray results showed that composition of CZTS NCs had a Cu and Zn-rich and S-poor. UV-vis spectroscopy results indicated that the absorption coefficient was over 10(4) cm(-1) in the visible region. The direct band gap energy of the CZTS NCs estimated at about 1.5eV, is ideal for its use in photovoltaic applications. (C) 2011 Elsevier B.V. All rights reserved.