Influential role of CdS film thickness in improving CdS/CdTe junction performance for solar cells: structural, optical, and electrical characterizations

CdS films of different thicknesses (d approximate to 100-300 nm) are deposited on the glass substrate by thermal evaporation technique. The structure of these films had been studied by Rietveld refinement and atomic pressure microscope. The films of CdS/glass show a wurtzite type structure. XRD calculations show that the lattice parameters a and c have changed, the microstrain decreases, and the crystallite size increases. The optical constants refractive index n, and extinction coefficient, k consequently band gap are estimated from SE via construction an optical model. The refractive index n of the CdS/glass films received from SE model increases with growing of CdS layer thickness that is credited to the rise of the size of the crystal. It was also found that when the thickness of the CdS layer increases, the general behavior of the extinction coefficient k of the CdS/glass film increases. In addition, it is found that the direct optical transition with energy band gap is compact from 2.45 (d = 100 nm) eV to 2.25 eV (d = 300 nm). The Ni/n-CdSe/p-CdTe/Pt heterojunction has been assembled. The dark (cutting-edge-voltage) characteristics of fabricated heterojunctions had been suggested at the different thicknesses of CdS, as well as for voltages ranging from - 2 to 2 V. Based on the dependence of the forward and reverse current at the voltage, the powerful and essential parameters related to the fabricated diode had been determined.

Automated summary

CdS films of different thicknesses were deposited on a glass substrate using thermal evaporation technique. The structure of these films, their optical constants, and energy band gap were studied. It was found that the lattice parameters and crystallite size changed with the CdS layer thickness, and the refractive index increased while the extinction coefficient and band gap decreased.