Study Of The Properties Of Tin Sulfide Films Prepared By Pulse-form Electro-deposition

Tin sulfide (SnS) has an optical band gap of 1.3eV, which is close to the optimal band gap 1.5eV. And it has a high absorption coefficient (α>10⁴cm^-1) and a high conversion efficiency of ²5%. In addition, elements Sn and S are abundant and non-toxic in nature, which has good compatibility to environment. Thus, it can be used as an absorbing layer material in the solar photovoltaic cells.Based on our previous research, the constant-potential and pulse-form potential electro-deposition were put forward to prepare SnS films, and the structure, composition and properties of the films were investigated.Firstly, the range of technical parameters, such as the ratio of ion concentration Sn²⁺/S₂O₃^2- , pH value and deposition potential, were roughly determined from the cyclic voltammetry experiment on ITO-coated glass substrate in different electrolyte solution. Then SnS films were prepared on the ITO glass substrate by the constant potential electro-deposition. The influence of the technical parameter on the composition ratio of films was studied through X-ray fluorescence spectrometer and XRD analysis. And the optimal technical parameter was acquired: pH=2.7, Sn²⁺/S₂O₃^2- =1/5, deposition potential E=-0.72^-0.75V (vs.SCE), total deposition time t=1.5h.Secondly, the SnS films were prepared by constant potential electro-deposition in the bath temperature of 30⁵0oC, and the influence of bath temperature on the surface micrograph, composition, structure and optical properties of the films was studied. With the bath temperature increasing, the films are compacter and the peaks of the XRD diffraction are stronger; the size of the crystal is changed from 14.87nm to 21.56nm; its band-gap is varied from 1.43eV to 1.27eV. When bath temperature T=40oC, the deposited films have good surface and structure, the composition ratio Sn/S is 1, and its direct band-gap Eg is 1.31eV.Lastly, the SnS films were prepared by pulse-form electro-deposition and the influence of V_off on the properties of films was studied when V_off was varied between -0.3V and 0.6V. When V_off is changed from 0.1V to 0.6V, all...