Chemically deposited Ni-doped CdS nanostructured thin films: Optical analysis and current-voltage characteristics

In the present work a cheap chemical bath deposition technique has been employed to prepare Ni-doped CdS (Ni: CdS) thin films and Ni: CdS/p-Si heterojunctions using different Ni concentrations varied from 0 to 7 wt %. The X-ray diffraction study confirms the cubic crystal structure for CdS and Ni: CdS thin films. The linear optical parameters of the CdS and Ni: CdS thin films were estimated via the transmission and reflection measurements at the wavelength range 400–2500 nm. The optical band gap was evaluated for the CdS and Ni: CdS thin films via Tauc's extrapolation procedure and were located to decrease from 2.49 to 2.21 by increasing the Ni doping concentrations from 0 to 7 wt %. The dark and illuminated current-voltage characteristics of the Ni: CdS/p-Si heterojunctions were studied at a temperature of 300 K. The influence of Ni doping concentration on the heterostructure parameters of the Ni: CdS/p-Si heterojunctions has been studied using thermionic emission theory. The ideality factor (n) of the fabricated Ni-doped CdS/p-Si heterojunctions were decreased from 3.46 to 2.59 by increasing the Ni doping concentration from 0 to 7 wt %. Both of sheet and shunt resistances were decreased by increasing the Ni doping concentration. The J-V measurements indicate that addition of Ni-doping to the CdS/p-Si heterojunction improve the photovoltaic parameters like the fill factor (FF), open circuit voltage (V_oc), and the solar efficiency (η).