Optimization of Zn concentration in chemically deposited (Cd_x-Zn_(1-x))S nanocrystalline films for solar cell applications

摘要

An attempt has been made to optimize the Zn concentration in chemically deposited (Cd-x-Zn1-x)S (x =0.2, 0.4, 0.6, 0.8) films on ITO substrate by varying the Cd/Zn composition ratio to enable them to absorb a sizable fraction of solar photons. The phase purity and nano-crystalline character of as-deposited films are established by x-ray diffractometer. Lattice parameters and band-gap values are found to change almost linearly with Cd/Zn composition ratio. The surface morphology supports the nano-crystalline nature of deposited films. The E-g values for (Cd-x-Zn1-x)S nanocrystalline films estimated from absorption spectra and corresponding Tauc's plots range from 2.63 to 2.81 eV. The optical behavior in terms of absorption and photoluminescence spectra suggests that these films are suitable for application in photovoltaic devices. The electrical resistivity of different (Cd-x-Zn1-x)S films has been measured as a function of Zn concentration. The efficiency of resultant CdTe/(Cd-x-Zn1-x)S cell is calculated to be approximately 11%.