Preparation And Characterization Of Tin Sulfide As A Solar Cell Material Grown By Pulsed Laser Deposition

The problem of energy saving and enviroment protection have been widely focused on in today's world.The solar cell,fabricated for energy saving and environmental protection,is a kind of optoelectronic device utilizing photovoltaic effect from solar energy.Tin sulfide(SnS) which has become a new type of solar cell materials for its non-toxic nature, abundance and high conversion efficiency,has attracted researchers'considerable attention both at home and abroad.Its direct band gap was reported to be in the ranges of 1.3~1.5eV,which is close to the optimum band gap for solar cells and has a theoretical energy conversion efficiency of 25%.And its optical absorption coefficient is larger than 104cm-1.The solar cell based on SnS can be solidified,filmed easily as well as small consumption.In a word,SnS is very suitable for the solar cell,and has become the first choice of manufacturing the third generation of thin film solar cells.In this thesis,tin sulfide(SnS) thin films were prepared by the pulsed laser deposition(PLD) technique.The dependence of the surface morphology,structure and composition,optical properties and electrical characteristics of the SnS films prepared by pulsed laser deposition on the growth substrate temperature was investigated.In order to improve the electrical properties of tin sulfide thin films,we also carried out a preliminary doping.Experiment and characterization results are presented as follows:1) The SnS thin film samples we prepared are the ones which have orthorhombic polycrystalline structure.And the SnS thin film samples prepared by PLD have significantly preferentially oriented along (111) plane,and in a certain range of substrate temperature,the higher the substrate temperature is,the more significant the preferential orientation of the sample is.2) The higher the substrate temperature is,the more uniform the growth of SnS grains on the surface will be,and the roughness increased at first then decreased.3) Absorption coefficients of the SnS thin film samples are as high as 105cm-1,and the lower the substrate temperature is,the higher the absorption coefficient will be.The direct band gap of SnS thin film is 1.39~1.46eV,and the indirect band gap is 1.25~1.38 eV.The band gap got its maximum at 200℃,and its minimum at 400℃.4) The conductivity of SnS thin film increased in magnitude as the substrate temperature increased,and the ratio of photo-conductivity and dark- conductivity got its maximum value when the substrate temperature is 200℃.5) The SnS thin film samples have photoluminescence property and have narrow emission peak at 820nm.The photoluminescence intensity decreased as the substrate temperature increased,which shows that the non-radiative recombination processes in the thin films increased as the substrate temperature increased.6) Doped SnS thin film with proper amount Cu (II) can increased the conductivity effectively.