Optimization of Zinc to Tin Ratio in a Sol Gel Precursor Solution on the Growth and Properties of Annealed CZTS Thin Films

Abstract

CZTS thin films were deposited by sol–gel spin coating method using precursor solutions prepared by dissolving copper acetate dihydrate, zinc acetate dihydrate, tin chloride and thiourea in methanol and monoethylamine then annealed in RTP furnace at 500 °C. Sol–gel precursor solutions were prepared with different Zn/Sn in a precursor solution and were annealed at different time intervals; and their effects on the optical and electrical properties of CZTS (Cu₂ZnSnS₄) films were investigated. The optical band-gap values were estimated to be between 1.30 and 1.88 eV while the absorption coefficients were in the range of 10⁴ cm^–1 in the visible region. The resistivity and carrier concentrations ranged from 13.12 to 2634 kΩ/□ and 10¹⁷ to 10²⁰ cm⁻³,respectively. The influence of Zn/Sn ratio and annealing time on structural properties of CZTS thin films are also discussed.

Keywords: CZTS; Cu₂ZnSnS_4; Kesterite; Zn/Sn ratio