Preparation And Optical Properties Of MAPbI₃/MAPbI_3-xCl_x Thin Films

In the past three years, inorganic-organic hybrid perovskite (CH3NH3PbI3, MAPbI3) has been investigated enthusiastically as one of the most promising materials for light harvester in solar cell, mainly due to its high overall cell efficiency, with certified values as high as 20.8%, wide spectral absorption range and low temperature process.In this thesis, MAPbI3 thin films were prepared on mesoporous TiO2 electrode with two-step solution method. Effects of main process parameters on the film structure, morphology and optical properties were characterized using X-ray diffraction (XRD), scanning electron microscople (SEM), energy dispersive X-ray spectroscople (EDS) and UV-visible spectrophotometer (UV-Vis).Using the traditional spin coating-dipping method, MAPbI3 thin films were prepared by dipping the precursor films of Pbl2 into the isopropanol solution of CH3NH3I (MAI) at different temperatures. It was found that with the increase of temperature, the transformation of Pbl2 into MAPbI3 was promoted and the size of particles and surface coverage of thin films were inproved. When the dipping temperature raise to 45℃, the thin film has been transformed into MAPbI3 completely, with the best surface coverage and light absorption. The particle size, surface coverage and absorption properties were affected as temperature further increased.In order to improve the properties of the thin films, the conversion from the PbI2 to MAPbI3 is accomplished by spin coating an upper layer of MAI on the precursor film followed by annealing at a high temperature.The results show that qualified films could be obtained when annealed at 110℃. Increasing the cycles of spin coating can promote the transformation PbI2 into MAPbI3 and the surface coverage of the thin film. Compared with MAPbI3, MAPbI3-xClx thin films prepared by several spin-coating method show larger grains with columnar structure, uniform surface and strong light absorption property.