Study On The Photoelectric Properties Of Perovskite Thin Films By Self-assembled Molecular Film Interface Modification

In perovskite solar cell devices,the deposition quality of the perovskite light absorbing layer and the stability of the carrier transport layer play a key role in the open circuit voltage,short-circuit current,and lifetime of the device.The commonly used materials of the hole transport layer in the carrier transport layer are mostly unstable organic materials（e.g.,PEDOT:PSS,PTAA,P₃HT）,so that the perovskite solar cell device has poor stability.Inorganic metal oxides are good choices for hole transport materials because of their good stability and high carrier mobility,e.g.,the Nickel Oxide（NiO）.The energy level of NiO matches with MAPbI₃（CH₃NH₃PbI₃）material,which can play the role for transporting hole and blocking electrons,thereby reducing carrier recombination.However,it is easy to form a charge defect state due to the presence of hydroxyl groups on the surface of NiO,and the crystalline quality of the perovskite film deposited on the surface of the NiO and the film coverage are poor.Which results in the redution of device performance.The previous studies have found that it can modify the interface by introducing a self-assembled molecular film with hydroxyl,amino,and pyridinegroups on the surface of the carrier transport layer.Which can not only passivate the surface,reduce charge defects,but also improve the film forming quality of perovskite film.In this dissertation,NiO with good stability was selected as the inorganic hole transport layer.On the one hand,the NiO film with good quality was pre-pared by magnetron sputtering.On the other hand,the self-assembled molecular film on the surface of the sputtered NiO film was used to modify the interface.Thereby it can passivate the NiO film surfaces,and improve the film quality of perovskite films,so that it improve device performance.The work of this disser-tation mainly includes three parts:the preparation and characterization of the hole transport layer of nickel oxide;the effect of the self-assembled molecular film interface modification of ethanolamine and ethylenediamine on the per-ovskite film and device;the preparation and characterization of theβ-alanine self-assembled molecular film.The first part is the preparation of NiO hole transport layer:NiO hole transport layer was prepared by magnetron sputtering.The effects of different oxygen-to-argon flow ratios on the performance of NiO films were studied.By means of X-ray Diffraction（XRD）,we can obtained the NiO film of preferable crystallinity in the pure argon atmosphere.At the same time,we also studied the influence of different sputtering time on the NiO film.we obtained that the NiO film for the coverage of the substrate after sputtering 20minutes is better than the sputtering 5minutes,by means of Standard Electronic Modules（SEM）and Air Force Manual（AFM）.In the second part is the interfacial modification of self-assembled mono-layers of ethanolamine and ethylenediamine.we mainly explore the interface modification on the surface of nickel oxide,which is based on the two kinds of organic small molecules:the ethanolamine which only includes amino and hy-droxy,and the ethanolamine only including amino-functional ethylenediamine.By means of the XRD,SEM and Photoluminescence（PL）of the characteriza-tion of the modified perovskite films before and after.Which show that the crystal quality of the perovskite films is enhanced and the crystal grains become larger after the modification with ethanolamine and ethylenediamine.The sur-face of the perovskite film become more and more smooth,but PL The spectrum shows that after the ethylenediamine modification,the hole extraction rate of the perovskite film does not change significantly,but after the modification by ethanolamine,the effective extraction rate of the hole and the device efficiency increases.The third part is the main content of this dissertation—the modification ofβ-alanine self-assembled molecular film interface is the influence of perovskite film.We used soaking method to study the film forming conditions of the self assembled monolayer ofβ-alanine of the substrate on the surface of the nickel oxide film by the before and after ultraviolet ozone treatment.We made some characterizations（e.g.,Contact angle,Infra-red Morphology Electrochemistry）of the assembled before and after perovskite film.The results indicate that after the UV ozone treatment and assembledβ-alanine molecular film,whoes hydrophilicity of the nickel oxide surface is enhanced;At the same time,the film formation quality and the photoelectric properties of the perovskite film were also studied.It indicates that when theβ-alanine self-assembled molecular film was assembled after ultraviolet ozone treatment,the crystal quality of the perovskite film was enhanced,the crystal grain became larger,and the absorption becomes increased.