Study On Ferromagnetic And Optical Properties Of Organic Semiconductor Materials

Compared with inorganic semiconductor materials,organic semiconductor materials have the advantages of high light absorption coefficient,simple preparation process and low cost,and are widely used in the fields of spintronics and photovoltaic.In the field of spintronics,spintronic devices based on organic semiconductors have two major problems:conductivity mismatch and metal electrode diffusion to the organic layer.The solution is to fabricate organic magnets by doping organic small molecular materials.Transition metal-doped organic small molecule materials have room temperature ferromagnetism,but the influence of metal clusters makes the magnetic source unclear.In the field of photovoltaic,organic-inorganic hybrid perovskite materials have been widely used because of their advantages such as direct and adjustable band gap,high carrier mobility and high light absorption coefficient,but organic-inorganic hybrid perovskite has the problem of low luminous efficiency.In this thesis,based on octahydroxy quinoline organic small molecule materials and organic-inorganic hybrid perovskite methylamine lead iodide,the following two works have been carried out:（1）Study the room temperature ferromagnetism of Al-doped octahydroxy quinoline iron film and analyze the source of magnetism.The Al-doped octahydroxy quinoline iron film was prepared by the vacuum thermal co-evaporation method,and the magnetic measurement by a physical property measurement system indicated that the Al-doped Feq₃film shows obvious ferromagnetic property even at room temperature.The FTIR and XPS spectra show that the doped Al atom reacts with the oxygen atom of octahydroxy quinoline to form the-O-Al-O-complex.First-principles calculations results indicated that compared with pure Feq₃cell,the energy differences between antiferromagnetic and ferromagnetic states became much larger after Al atoms doped into Feq₃cell.This may explain the room-temperature ferromagnetism observed in the prepared Al-doped Feq₃film.（2）Preparation and photoluminescence characterization of methylamine lead iodide perovskite films on as-grown GaN substrates and nano-porous GaN distributed Bragg reflectors（NP-GaN DBRs）were studied.Two kinds of substrates were treated with ultraviolet ozone to reduce the contact angle between the perovskite precursor solution and the substrate and improve its surface activity.Methylamine lead iodine perovskite films with good crystal quality were prepared by one-step solution method in air environment.The quality and photoluminescence（PL）strength of the perovskite films prepared on the unetched GaN substrate and the nano-porous GaN distributed Bragg reflectors were further investigated.By comparison,it was found that the PL strength of the perovskite films prepared on the nano-porous GaN distributed Bragg reflectors increased significantly,which was about 3.5times.