Temperature dependent characterizations of chemically deposited (Cdx-Zn1-x)S nanocrystalline films for solar cell applications

Abstract

We report on the deposition of (Cdx-Zn1-x)S (x = 0.85, 0.75, 0.65, 0.55) ternary alloys on FTO substrate by chemical bath deposition (CBD) technique. The structural transformation, texture and optical properties of these films deposited at different temperatures (60 °C, 70 °C, 80 °C and 90 °C) are investigated and analyzed. X-ray diffraction patterns show hexagonal phase of deposited films with the most intense peak corresponding to (002) plane. Flower-like structure with layer by layer growth is revealed through field emission scanning electron microscopy (FESEM). A uniform and adherent surface is observed in different films, which signifies the CBD impact on the material. The roughness of the film surface and the thickness in the nano-range are identified by the atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM), respectively. The energy dispersive X-ray (EDX) spectra confirm the elemental composition in the deposited films. The absorption edges shift towards the lower wavelength region with an increase in temperature of deposition, and the band-gap values (Eg) estimated with Tauc's plots range from 2.58 eV to 2.66 eV. Optical constants are also measured from the transmittance spectra. The transmission is found to be very high in the visible region. The efficiency of the (Cdx-Zn1-x)S/CdTe solar cell is estimated to be 8.19%. The key outcomes of our work are low absorption and high transmission of the deposited films making them suitable for fabricating an efficient PV device.