Effect of annealing process on the properties of Cu2ZnSnS4 thin films

•Preparation of Cu2ZnSnS4 (CZTS) thin films by spray pyrolysis using an aqueous solution.•Effect of nitrogen annealing temperature on the physical properties of CZTS.•Annealed CZTS thin films become Cu poor and Zn rich.•Crystallinity increase after annealing process.•Confirmation of the kesterite structure of CZTS (Raman spectroscopy).

Sprayed Cu2ZnSnS4 (CZTS) thin film prepared from an aqueous solution is annealed in nitrogen atmosphere at 450, 500 and 550 °C during 60 min. The effect of nitrogen annealing temperature Ta on the physical properties of CZTS thin films has been investigated. As-deposited film is Cu rich and Sn poor. After heat treatment process, CZTS thin films become Cu poor and Sn rich. Moreover, upon nitrogen annealing, a higher crystallite size of (1 1 2) diffraction peak, of kesterite crystal structure, is observed at Ta = 500 °C. The annealing temperature Ta significantly influences the surface morphology of the thin film annealed at 500 °C. Electrical properties exhibit an enhancement also after thermal annealing process. Optical analysis shows that the band gap energy of as-deposited CZTS thin film is about 1.67 eV; whereas it is improved reaching 1.52 eV after thermal treatment at 500 °C.

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