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

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.

Thickness dependency of nonlinear optical properties in ITO/Sn composite films

In this study,a batch of indium tin oxide(ITO)/Sn composites with different ratios was obtained based on the principle of thermal evaporation by an electron beam.The crystalline structure,surface shape,and optical characterization of the films were researched using an X-ray diffractometer,an atomic force microscope,a UV-Vis-NIR dual-beam spectrophotometer,and an open-hole Z-scan system.By varying the relative thickness ratio of the ITO/Sn bilayer film,tunable nonlinear optical properties were achieved.The nonlinear saturation absorption coefficientβmaximum of the ITO/Sn composites is−10.5×10^(−7)cm/W,approximately 21 and 1.72 times more enhanced compared to monolayer ITO and Sn,respectively.Moreover,the improvement of the sample nonlinear performance was verified using finite-difference in temporal domain simulations.

Determination and Analysis of Optical Constant of Annealed Sn_2Sb_2S_5 Thin Films

The effects of annealing on structural, optical and electrical properties of Sn2Sb2S5 thin films were studied. Sn2Sb2S5 thin films were deposited on no-heated glass substrates by single source vacuum evaporation method. The as- deposited films were annealed in air for 1 h at 100, 200 and 300 ℃. XRD study shows that annealed films are crystallized according to the preferential orientation （602）. Optical measurements show that the thin films have relatively high absorption coefficients in the range of 10s-106 cm-1 in the energy range of 2-3.25 eV. It is also found that Sn2Sb2S5 exhibit two optical direct transitions. The models of Wemple-DiDomenico and Spitzer-Fan were applied for the analysis of the dispersion of the refractive index and the determination of the optical and dielectric constants. The electrical resistivity measurements are recorded, and two activation energy values are determined. The layers annealed at 200 and 300 ℃ exhibit a resistive hysteresis behavior. The properties reported here offer perspective to Sn2SbES5 for its application in many advanced technologies.