One-step spray of Cu2NiSnS4 thin films as absorber materials for photovoltaic applications

A simple one-step «Spray Pyrolysis» technique was developed for preparing Cu2NiSnS4 (CNTS) thin film followed by an annealing treatment process. Originally, the spray technique was successfully used to deposit the thin film onto glass substrate at 250 °C for 60 min spray duration. Again, the deposited thin film was annealed in a sulfur atmosphere at a temperature of 500 °C during 30 min. The sulfured thin film exhibits (111), (220) and (311) orientations correspond well to the cubic CNTS structure and other impurity compounds. The SEM data exhibit a uniform, rough and compact topography of CNTS thin films with an average-thickness of 1.36 µm. The absorption coefficient is found to be higher than 104 cm−1 in the visible region while the direct band energy of 1.62 eV, which is eminently suitable for use as an absorber in the solar cell. The complex impedance diagrams indicate the decrease of resistance by increasing temperature, which attributes to a semiconductor behavior. The close values of activation energies 0.63 and 0.54 eV determined from both angular frequency and DC conductivity indicate that the carrier transport mechanism is thermally activated.