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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