Preparation And Photovoltaic Properties Of Inorganic Perovskite Nanofiber Membranes

Perovskite solar cells have attracted much attention due to their high photoelectric conversion efficiency,solution processing technology,and low cost.As the core of perovskite material,its morphology,structure and performance significantly affect the performance of the cell.However,the poor stability and brittleness of perovskite restrict the development and application of perovskite solar cells.Therefore,the research of perovskite solar cells mainly focuses on improving the efficiency and stability of the cell by means of interface modification,composition regulation,material structure design and device packaging.During the study of perovskite materials,it was found that inorganic perovskite materials have relatively excellent thermal and humidity stability.In addition,one-dimensional materials have good charge transfer properties.In theory,one-dimensional inorganic perovskite nanofibers can build efficient and stable perovskite solar cells.Therefore,based on the inorganic perovskite material CsPbX3(X=Br or I),an inorganic perovskite composite nanofiber membrane was prepared by electrostatic spinning method.Subsequently,the perovskite nanofiber film was used as a light absorbing layer to assemble perovskite solar cells.The main contents of this article are as follows:(1)In an open air environment,CsPbBr3/PVP/PAN nanofiber membranes were prepared by a simple one-step method using electrostatic spinning technology.The influence of the molar ratio of PbBr2 to CsBr in the electrospinning solution on the structure and properties of the electrospun nano fiber membranes was studied.The research showed that with the increase of the molar ratio of PbBr2/CsBr,the mosaic amount of CsPbBr3 crystals on the surface of nano fibers was increasing.When the molar ratio of PbBr2/CsBr is 3:1,dense CsPbBr3 crystals were embedded on the surface of the nanofibers.However,CsPbBr3 crystals were unevenly distributed and only exists on some nano fibers.When the molar ratio of PbBr2/CsBr further increased to 4:1,dense CsPbBr3 crystals were embedded on the surface of the nano fibers,and evenly existed on each nanofiber.In addition,perovskite nanofiber membranes prepared in different molar ratios have superior light absorption properties.The perovskite solar cells assembled from a perovskite composite nanofiber membrane have a low photoelectric conversion efficiency.The highest photoelectric conversion efficiency is only 1.10%(4:1).This is mainly due to the presence of polymers PVP and PAN in inorganic perovskite nanofiber membranes prepared by electrospinning,which affect the transport of free electrons and free holes.Secondly,the CsPbBr3 nanocrystals embedded on the surface of the inorganic perovskite composite nano fiber membrane prepared by one-step method are not uniform.However,the one-dimensional perovskite nanofiber membrane prepared by the electrospinning method has many advantages such as good flexibility,convenient transfer,no limitation of the preparation process,and large-area preparation.(2)CsPbBr3/PVP/PAN composite nanofiber membrane was prepared by two-step method of electrostatic spinning and spin coating.First,PbBr2/PVP/PAN composite nanofiber membrane was prepared by an electrostatic spinning method,and then a CsBr methanol solution was spin-coated on the PbBr2/PVP/PAN composite nanofiber membrane to obtain a CsPbBr3/PVP/PAN composite nanofiber membrane.It was found that with the increase of the content of PbBr2 in the PbBr2/PVP/PAN composite nanofiber membrane,the amount of CsPbBr3 on the surface of the composite nanofiber increased.When the PbBr2 concentration was increased to 2mol/L,the CsPbBr3 crystals were very densely embedded on the surface of each nanofiber.With the increase of PbBr2 concentration,the light absorption properties of the prepared inorganic perovskite composite nanofiber membranes increase.The PL spectrum shows that the recombination rate of free electrons and free holes decreases with increasing PbBr2 concentration.Perovskite solar cells constructed with two-step inorganic perovskite composite nanofibers achieved a photoelectric conversion efficiency of 2.00%(3mol/L),which is slightly higher than the one-step method for preparing perovskite nanofiber membranes.(3)On the basis of preparing PbBr2/PVP/PAN composite nanofiber membranes by electrospinning,CsPbIBr2/PVP/PAN composite nanofiber membranes with narrower band gaps were prepared by solution immersion method and solution spin coating method,respectively.By controlling the composition of perovskite,a narrower band gap perovskite material was obtained.The results show that the immersion method allows PbBr2 in PbBr2/PVP/PAN nanofibers to fully react with CsI to form a continuous and complete coated CsPbIBr2 crystal.While the CsPbIBr2/PVP/PAN nano fibers prepared by the solution spin coating method do not react with Csl Completely dispersed granular crystals were formed.In addition,the light absorption and PL spectrum peak strength of the perovskite composite film prepared by the solution immersion method are better than those prepared by the spin coating method.The CsPbIBr2/PVP/PAN nanofiber film prepared by the solution spin coating method has a photoelectric conversion efficiency of about 1.75%,while the nanofiber film prepared by the solution immersion method has a photoelectric conversion efficiency of 2.83%.The photoelectric conversion efficiency of CsPbIBr2/PVP/PAN nanofiber membrane-based solar cells is slightly higher than that of CsPbBr3/PVP/PAN composite nanofiber membranes.This is mainly due to the narrower band gap of CsPbIBr2 and the surface of CsPbIBr2 composite nanofibers Perovskite crystal coating is more complete.