Synthesis Of Novel Organic-Inorganic Hybrid Perovskites Towards Spintronic Devices

Spintronic devices offer much more advanced function compared with conventional electronic devices,therefore have attracted great attention in recent years.However,the developments of organic spintronic devices are limited by the lack of high-performance materials.The organic-inorganic hybrid perovskite structure integrates many advantages of organic materials and inorganic materials,such as the structural diversity and functionality of organic materials;the magnetic properties of inorganic materials and high carrier mobility,make this type materials as an ideal platform for design and synthesis functional materials.However,magnetic materials and spin-related devices based on perovskite structure are rarely reported.This thesis is motivated by the urgent needs of novel functional magnetic molecular materials that can be applied in future organic spintronic.A series of new two-dimensional hybrid perovskite ferromagnets were designed and synthesized.White light emission,thermochromism,chirality,ferromagnetism and ferromagnetic resonance were achieved through precisely adjusting the organic ammonium ions,metal ions,and halogens.Further,using these new materials,field-effect transistors,photodetectors and spin-injection devices were fabricated,and good device performance was obtained.This thesis provides a new strategy for creating new functional materials using perovskite structure,especially thermochromic ferromagnets and chiral ferromagnets,which lays the foundation for the further development of novel magnetic materials for spintronics.The main content of this thesis are listed below:Chapter one:The development of organic-inorganic hybrid perovskite materials are reviewed and discussed.The functionalities of organic-inorganic hybrid perovskite materials are elaborated,the research progress of perovskite materials in the field of optoelectronics and magnetism is discussed,and the research status of perovskite materials in the field of spintronics is summarized.At last,the motivation of the research in this thesis is introduced.Chapter two:Two new two-dimensional hybrid perovskites,(PED)CuCl4 and(BED)2CuCl6,were synthesized,both of which exhibit reversible thermochromism,significant changes in conductivity with temperature,and strong ferromagnetism.When the temperature changes,the colors of(PED)CuCl4 and(BED)2CuCl6 crystals change reversibly between yellow-brown and red-brown.The thermochromic working temperature of(BED)2CuCl6 reaches 443 K.The conductivity changes of(BED)2CuCl6 with temperature by more than 6 orders of magnitude.Magnetic tests show that(PED)CuCl4 and(BED)2CuCl6 are ferromagnetic substances with a Curie temperature of about 13 K.Integrating a variety of stimulus-response characteristics into two-dimensional hybrid perovskite will greatly broaden its scope of application and is expected to provide new functional materials for potential applications in optoelectronics and sensor devices.Chapter three:By introducing chiral ammonium ions into the perovskite structure,two new chiral perovskites(R-MPEA)2CuCl4 and(S-MPEA)2CuCl4 were synthesized.Circular dichroism spectrum and magnetic test results show these two materials are chiral ferromagnets.The saturation magnetization of(R-MPEA)2CuCl4 and(S-MPEA)2CuCl4 reaches 12.5 emu g-1,which is the highest value among perovskite magnets.We have further successfully characterized the magnetic chiral dichroism of the perovskite material system,indicating that such materials have application potential in magneto-optical devices.This innovative research opens up a new way to construct a new type of multifunctional chiral ferromagnet,highlighting the potential of developing a new generation of perovskite-based spintronics.Chapter four:A series of new two-dimensional hybrid perovskites were designed and synthesized,which showed white light emission and field-effect characteristics.The chromaticity coordinates of(BED)PbBr4 are(0.34,0.44),which is close to an ideal white light emitter of(0.33,0.33).The effects of organic amine components such as PEA/PED/BED on the luminescence and conductive properties of the material were further studied.By replacing Pb with Sn,the band gap of the material was reduced and a field-effect transistor was constructed.This work provides new ideas for using perovskite materials to achieve both white light emission and field-effect transistor properties.Chapter five:Flexible near-infrared photodetector based on MAPbI3/PCDTPT composite is fabricated,which showed fast light responsiveness,repeatability and excellent stability.Using MAPbI3 single crystal/PCDTPT complex,higher device efficiency is achieved than thin film.The control of substrate temperature on the morphology of perovskite films was studied,and the influence of incident light wavelength and energy on device responsiveness was analyzed.Chapter six:Using(BED)2CuCl6 as a ferromagnetic insulator,(BED)2CuCl6/Pt inverse spin Hall effect devices were prepared.The effects of temperature,frequency and Pt thickness on the ferromagnetic resonance signal were systematically studied,and the variation of the width and resonance field were analyzed.Secondly,we prepared Hall effect devices based on MAPbBr3 crystals and characterized the carrier mobility.Finally,an inverse spin Hall effect device based on organic polymer PBTTT was constructed,the ferromagnetic resonance phenomenon of the device was preliminarily studied,and the variation rule of line width and resonance field with frequency was summarized.