Study Of SnS,ZnS Thin Films And Devices By PLD

SnS thin film is a novel photovoltaic materials. it is suitable to be optical absorption layer of solar cells and optoelectronic devices. As ZnS thin film has a high visible light transmittance and good photoelectric properties, it is suitable for solar sell’s window layer.SnS and ZnS thin film have a good promise in heterojunction solar cells. In this thesis, study of SnS and ZnS thin films and devices by PLD, the influence of thermal annealing temperature on the properties of SnS thin films, as well as the the influence of laser fluence and repetition rate on the properties of ZnS thin films, and the SnS/ZnS heteroj unction device were studied.SnS thin films were prepared on glass substrates by pulsed laser deposition and then rapidly annealed in Ar atmosphere. The annealing temperature increases from 100℃ to 400℃. The pulsed laser energy is 90mJ and 140mJ. The crystal structure, chemical composition, surface morphology, optical properties of SnS thin films were investigated by X-ray diffraction, Raman spectroscopy, X-ray energy disperse spectroscopy, atomic force microscopy and ultraviolet-visible-near infrared spectrophotometry. The results show that the SnS thin film demostrates good crystalline quality, highly preferentially oriented growth, ideal atomic ratio (Sn:S=1:1.03) in close proximity to stoichiometry and the order of 105cm-1 of absorption cofficient under the condition of 140mJ of the plused laser energy and 300℃ of the annealing temperature.A series of ZnS thin films have been prepared on glass substrates with different pulsed laser fluence and pulse repetition rate by pulsed laser deposition technique. The crystal structure, and optical properties of the ZnS thin films were characterized by X-ray diffraction, and ultraviolet-visible-near infrared spectrophotometer. The crystallinity, grain size, optical constants and bandgap of the thin films were calculated and analyzed. The results show that the prepared ZnS thin films are well crystallized with (002) preferred orientation. While a high laser fluence together with a low pulse repetition rate is the condition for growth of high quality ZnS thin films. The ZnS thin film prepared under the optimum condition that is the laser fluence of 7.5J/cm2 together with pulse repetition rate of 2Hz has a single-phase wurtzite structure, the highest crystallinity and degree of preferred orientation, the packing density of 0.967, the high transmittance in the visible region, and the direct bandgap of 3.55eV.The In/p-SnS/n-ZnS/In heterojuction device was fabricated on glass substrate by pulsed laser deposition. The current-voltage characteristics show that the device has good rectifying characteristics and weak photovoltaic properties. Under the illumination conditions of 0.35mW/cm2, the device has the open-circuit voltage of 0.34V, short-circuit current of 1.41×10-9A, short-circuit current density of 7.01×10-9A/cm2 and fill factor of 25.4%.