Investigation on dispersive optical constants and microstructural parameters of the absorber CuSbS2 thin films

• CuSbS2 thin films were grown on heated substrates using thermal evaporation.
• The effect of annealing in vacuum was studied.
• The crystallinity of the films increased after annealing.
• The microstructural and optical constants were determined.

In this work, the thermal annealing effects on the microstructural, optical constants and electrical properties of as-grown vacuum evaporated CuSbS2 thin films have been investigated. The annealing temperatures in vacuum were varied in the range 100–220 °C. CuSbS2 thin films were deposited on heated glass substrates. These films were characterized for their structural, optical and electrical properties using X-ray diffraction (XRD), optical measurement and hot probe method. The lattice parameters, crystal strain ɛ and dislocation density δ are calculated. The optical constants of the elaborated films were determined, in the spectral range 300–1800 nm. The values of the optical band gap energy ranged between 1.39 and 1.75 eV. The dispersion of the refractive index and extinction coefficient in the infrared region are adequately explained using a single oscillator model. The different values of the dispersion energy Ed, the oscillator energy E0, the high frequency dielectric constant ε∞ε∞ and the ratio of the carrier concentration to the effective mass were estimated according to the models of Spitzer-Fan and Wemple_DiDomenico. The electrical conductivity measurements suggest that obtained films show ‘mineral materials’ behavior with conductivity of 10−4 Ω−1 cm−1. The annealed layers exhibit an obvious p_type semiconductor.