Variable-Range Hopping Versus Inter-Grain Tunneling in Cu2ZnSn(SxSe1-x)4 Thin-Films Prepared by Spray Pyrolysis

32nd European Photovoltaic Solar Energy Conference and Exhibition; 1186-1189
Thin Cu2ZnSn(SxSe1-x)4 films with x = 1.0 and 0.85 were prepared by the spray pyrolysis method with subsequent annealing in the presence of elemental sulfur or selenium. The surface sensitive Raman measurements indicated a high crystalline quality of all samples and absence of secondary phases. Small amount of Cu2-xS secondary phase was detected from grazing incidence X-ray diffraction patterns (information depth of about 500 nm). The resistivity, (T), is governed by the Mott variable-range hopping conduction at high temperatures, when the mean hopping length Rh (T) exceeds the mean distance between the acceptors, RA, but is still smaller than the typical inter-grain distance, aig. However, with lowering the temperature the resistivity becomes dominated by inter-grain tunneling, provided that Rh (T) > aig. The analysis of the (T) function has yielded the values of the acceptor concentration and the localization radius, with the evidence that all the samples are characterized by a state far different from the metal-insulator transition. The radius of the mean size grain as well as values of aig were in addition determined.