Study Of CH₃NH₃PbI₃、SnS Thin Films And Devices

The hybrid organic-inorganic perovskite materials are novel light absorption materials, such as CH₃NH₃PbI₃. Because of its favourable optical and electrical properties, CH₃NH₃PbI₃ is suitable to be used as the absorption layer of solar cells and photoelectric device. SnS has a good application prospect, for its abundant resources and high absorption ability in the range of visible light. Therefore, the preparation of high quality CH₃NH₃PbI₃ and SnS thin films and devices, and the study of its related properties are important in research field of solar cells and photoelectric devices. In this study,CH₃NH₃PbI₃ thin films and devices were prepared by pulsed laser deposition, and the SnS thin films were prepared by RF magnetron sputtering technique. The effect of the different molar ratios and pulse repetition rates on the properties of CH₃NH₃PbI₃ thin films, the effect of the various sputtering power on the properties of SnS thin films,and the characteristics of heterojunction devices based on CH₃NH₃PbI₃ thin films were studied.CH₃NH₃PbI₃ thin films were prepared on glass substrates by pulsed laser deposition at room temperature. The crystalline structure, phase composition, chemical composition,surface morphology,optical and electrical properties of CH₃NH₃PbI₃ thin films are analysed by X-ray diffraction （XRD）, Raman spectroscopy （Raman）, energy dispersive X-ray spectroscopy （EDS）,atomic force microscopy （AFM）,field emission scanning electron microscopy （FE-SEM）, ultraviolet-visible-near infrared spectrophotometry （UV-Vis-NIR） and Keithley 4200-SCS semiconductor parameter analyzer. The results show that all the CH₃NH₃PbI₃ thin films grown under various molar ratios of target and pulse repetition rates are crystallized. Under the condition of target’s molar ratio （PbI2:CH3NH3I） of 1:10 and pulse repetition rate of 8Hz,the sample S3 has a high crystalline quality,pure-phase CH₃NH₃PbI₃ thin film and a nearly stoichiometric atomic ratio. The sample is aligned along （002） preferred orientation.And the sample has high light harvesting capability in the visible region and the direct band-gap of 1.66 eV.SnS thin films were prepared on glass substrates by RF magnetron sputtering technique in room temperature and then were rapidly annealed. The crystalline structure,phase composition, and relevant optical properties of SnS thin films grown under various sputtering power （60-120W） are investigated by X-ray diffraction （XRD）,Raman spectroscopy （Raman）, and ultraviolet-visible-near infrared spectrophotometry（UV-Vis-NIR）. The results show that all the prepared thin films are crystallized. The crystalline quality of thin films are improved by the increase of sputtering power. Under the condition of sputtering power of 100W, the sample has high crystalline quality, high degree of preferential orientation and the least strain, being a pure-phase SnS thin film.And the sample has high light harvesting capability in the visible region, the absorption coefficient of 105cm-1 and the direct band-gap of 1.54 eV.The CH₃NH₃PbI₃/n-Si heterojunction device was fabricated by pulsed laser deposition. And the electrical and photoelectric properties of the device were analysed by a semiconductor parameter analyzer. The Ⅰ-Ⅴ characteristics of the heterojunction exhibit a good rectifying behavior and fast photoresponse. The rise and fall time of the device were measured to be 58.8 μs and 1.9 μs, respectively.