Surface Modification Of Mesoporous TiO₂ Layers And Preparation And Stability Of CH₃NH₃PBI₃ Thin Films

Due to low preparation cost,high light absorption coefficient and high photoelectric conversion efficiency,perovskite solar cells have attracted extensive attention from the scientific community.In the process of producing perovskite solar cells,mesoporous TiO2 electron transport layers and perovskite absorption layers play crucial roles.The paper regards mesoporous Ti02 and CH3NH3PbI3 films as the research objects.First of all,studied the film performance of CdO deposited on the mesoporous TiO2,and then research the film performance and stability are discussed through technology of improving CH3NH3PbI3 film preparation and method of adding solventto.The main research includes two parts as follows:Spinning cadmium nitrate on mesoporous Ti02,and getting metal oxide CdO though high temperature,the result shows that the size of mesoporous Ti02 modified by CdO turns from 23 to 20 nm.The transmittance of Ti02 thin films modified by CdO increases and absorption coefficient decreases.The Ti02 band gap turns from 3.5 to 3.6 eV.The CH3NH3PbI3 film prepared on the layer of Ti02 modified by 0.05M CdO has lots of advantages,such as high coverage,good crystalline,enhenced light absorption ability and reduced lattice defects.The thickness of CdO-TiO2/CH3NH3PbI3 film is 650 nm,and it is similar to the thickness of high-quality mesoporous perovskite reported by literature.In order to optimize the CH3NH3PbI3 film performance,a perovskite CH3NH3PbI3 absorption layer is prepared by using improved two-step continuous deposition.Studying their effects on the performance and stability about CH3NH3PbI3 layer,by optimizing the spin coating process and additive handling.The result indicate that film density is large and has no pore with the improved process speed approached 4000r.Besides,the size of grains is 200 nm and has no PbI2 diffraction peak.Dropping chlorobenzene and isopropyl alcohol promotes the thin-film crystalline.Chlorobenzene can effectively optimize the film surface morphology and coverage.In terms of stability,improved process film could place in the air for 168 hours.CH3NH3PbI3 diffraction peak,light absorption spectrum,and microstructure obviously have not any changes,so we conclude that the improved technology has a good stability.At last,adding chlorobenzene also could prevent perovskite from decomposition so as to enhance the stability of the film.