Enhancement in photovoltaic properties of Nd:SnS films prepared by low-cost NSP method

摘要

The inner transition metal(ITM) neodymium(Nd)-doped tin sulfide(Nd:SnS) thin films with various Nd concentrations were coated by nebulizer spray pyrolysis(NSP) technique at 350℃. All the coated films were analyzed for their structural, optical and photoelectrical properties. X-ray diffractometer(XRD) study showed(111) direction as the highly preferred orientation with orthorhombic crystal structure for all the films. The intensity of the peaks was found to increase until 5 at% Nd doping and then reduced for higher(7 at% Nd) doping concentration. Atomic force microscopic(AFM) images of the films proclaimed an increase in the surface and line roughness of the films by increasing Nd concentrations.Optical analysis on the films showed a variation in energy gap from 2.05 to 1.69 eV when the doping concentration increased from 0 at% to 7 at%. At 5 at% Nd doping, the photoluminescence(PL) spectra displayed a single strong emission peak at 723.1 nm with enhanced intensity corresponding to near-band-edge emission. All the SnS thin films exhibited p-type behavior with the lowest resistivity of ~ 4.311 Ω·cm and high carrier concentrations of ~ 1.441 × 10^(17)cm^(-3) for 5 at% Nd doping level as observed from Hall effect studies. Furthermore, fluorinedoped tin oxide(FTO)/n-CdS/p-Nd:SnS hetero-junction solar cells were prepared and the current–voltage curve in dark and light condition was obtained for the device. An efficiency of 0.135% was observed for the solar cell fabricated with 5 at% Nd-doped SnS thin film.