Preparation Of Cu₂ZnSnS₄and SnS Thin Films And Their Application In Solar Cells

In this thesis, Cu₂ZnSnS₄（CZTS） and tin monosulfide （SnS） semiconductingmaterial powder were prepared by hydrothermal method and solution method,respectively. The CZTS and SnS thin films were deposited using vacuum thermalevaporation technology from the as-prepared CZTS and SnS semiconductingmaterial powder source, followed by annealing at different temperatures under highpurity N2atmosphere. X–ray fluorescence spectrometry （XRF） was applied todetermine the chemical compositions of CZTS and SnS semiconducting materials.The influence of annealing temperature on the compositions, crystal structures,surface morphology, direct band gaps and electrical properties of the CZTS and SnSthin films were investigated by Energy dispersive X-ray spectroscopy （EDS）, X-raydiffraction （XRD）, scanning electron microscope （SEM）, ultraviolet–visible–nearinfrared （UV–Vis–NIR） and Hall measurements, respectively.The results revealed that the chemical compositions of CZTS and SnSsemiconducting materials were Cu_1.90Zn_0.94Sn_1.00S_4.30and Sn_1.00S_1.11and nearlystoichiometric. After annealing, both of the as-deposited CZTS and SnS thin filmswere transformed from amorphous state into crystalline state and the ranges ofabsorption to light were extended. Along with the increase of annealingtemperature, CZTS thin films grew with better crystallinity and showed a preferred（112） orientation. When the annealing temperature up to350℃, the surface of theCZTS thin film appeared fall off phenomenon. The direct band gaps of as-depositedCZTS thin films were decreased from1.87eV to1.57eV,1.55eV and1.37eV afterannealing at200℃,300℃and350℃, respectively. Combining with the XRDpatterns and EDS data, the SnS thin films mainly consisted of Sn₂S₃phase, andbegan to be oxidated after annealing at300℃, and was almost oxidized into SnO₂when the annealing temperature was increased to400℃. Based on all of thecharacterization, the CZTS thin film after annealed at300℃, which exhibited ap-type conductivity by the Hall measurements, was used to the fabrication of thethin film solar cells with the structure of FTO/CdS/CZTS/Al contact and obtained aconversion efficiency of0.36%under AM1.5and100mW·cm^-2intensity.