Controllable Preparation Of Planar Perovskite CH₃NH₃PbI₃ Thin Film For Photovoltaic Properties Studys

In recent years,global warming,environmental pollution,energy crisis threat human’s healthy and economic sustainable development.Because solar energy will never be used up,more and more scientists put their eyes on it.At present,the most mature and widely used solar cell is silicon solar cell,it,s conversion efficiency has reached 25%.However,the cost of preparation of silicon solar cells is very high,which limits its application.This years,The rapid development of perovskite solar cells has attracted wide attention,at the time there are many problems must to be solved if we want to put it into commercial production.There is very a small amount of solvent which can simultaneously dissolve organic matter and inorganic matter,and the traditional solvents（such as DMF）is not conducive to control the grain size of the film;The stability of the cell is very poor and difficult to achieve commercial requirements.In this paper,the green organic solvent 1-ethyl-2-pyrrolidone（NEP）was used to dissolve PbI₂ and PbBr₂ powders.The PbI₂ and PbBr₂ precursor films were prepared by dip-coating method.The effects of different temperature and time on the morphology and grain size of PbI₂ precursor films were studied.The results show that the PbI₂ precursor film has good crystallinity and compactness when heated at 70℃for 20min.PbI₂ precursor film prepared under this condition was used for subsequent experiments.Secondly a vapor-assisted solution process was used to deposit CH₃NH₃I on the PbI₂ film.The effects of evaporation time and evaporation temperature on the quality of CH₃NH₃PbI₃ film were investigated.The results show that the CH₃NH₃PbI₃ film prepared at 150℃for 2h has the best density and surface smoothness.The solar cells with the structure of FTO/c-TiO₂/CH₃NH₃PbI₃/Spiro-OMe-TAD/Ag were prepared by using this film,and the photoelectric conversion efficiency is 10.2%.In addition,the influence of the depositing process of CH₃NH₃Br on PbI₂ precursor film and depositing CH₃NH₃I on PbBr₂ precursor film was compared on the quality of CH3NH3Pb（I1-xBrx）3 absorption layer.And the influence of the x value on the stability of the perovskite absorption layer was analyze.The results show that when the x value is 0.5,CH₃NH₃Pb(I_1-xBr_x)₃ exhibits better stability.