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二维有机单晶的可控制备及光电性能研究
Controlled Preparation and Optoelectronic Properties of Two-Dimensional Organic Single Crystals
【作者】 王颖；
【导师】 李荣金；
【作者基本信息】 天津大学 ， 化学， 2021， 硕士
【摘要】 二维有机单晶的缺陷密度低并且没有晶界,是研究构效关系的理想载体,也是制备多种有机光电器件的理想材料,在有机自旋阀(OSVs)、有机场效应晶体管(OFETs)、有机发光二极管(OLEDs)和有机光伏器件(OPVs)等领域有重要科学意义和应用价值。然而,目前二维有机单晶的可控生长是一个挑战,这限制了其光电性能的研究和器件应用。本论文发展了二维有机单晶的可控制备策略,并探索了其自旋和电荷传输特性。主要研究成果如下:(1)在液态衬底表面通过调节半导体溶液浓度生长了不同厚度的6,13-双(三异丙基甲硅烷基乙炔基)并五苯(TIPS-pentacene)的大面积二维有机单晶,进而制备了首例可工作的垂直有机自旋阀,探索了有机半导体(OSC)的本征自旋输运特性。选择甘油作为液态衬底,其高表面张力和高粘度可以促进蒸发过程中溶液的铺展并固定溶液的位置,这有利于制备薄且大面积的单晶。通过调节溶液浓度获得不同厚度的单晶并转移至图案化铁磁(FM)电极的衬底上以构筑单晶有机自旋阀。成功探测到了TIPS-pentacene单晶在不同温度和不同厚度下的磁电阻(MR)响应。基于269 nm厚的二维有机单晶做中间层获得了高达17%的磁电阻值。更重要的是,在厚达457 nm的单晶中仍然可以观察到自旋输运,比多晶薄膜的自旋输运长度大得多。本研究为构建单晶有机自旋阀提供了一种通用的策略,为基于有机半导体本征自旋传输特性的研究奠定了基础。(2)提出了双相提拉法制备大面积二维有机单晶的策略,并研究了其光电性能。与传统的单相提拉法相比,双相提拉法提供了较大的溶液比表面积,在液?气界面处获得了更大的蒸发通量,所以更容易发生异质成核,从而更有利于制备大面积高质量薄膜。详细研究了衬底类型、溶剂类型、溶液浓度、提拉速度和有机溶液滴加量对薄膜形貌的影响,成功制备了纳米级薄的单晶薄膜,并用作OFET的活性层,获得了优异的光电性能。本研究为制备大面积超薄有机单晶提供了一种快速有效的新方法,为进一步研究二维有机单晶的光电性能提供了新思路。
【Abstract】 Two-dimensional(2D)organic single crystals contain minimal defects density and no grain boundaries,which are ideal carriers for studying the structure-property relationships and ideal materials for the preparation of a variety of organic optoelectronic devices.They have important scientific significance and application value in the fields of organic spin valves(OSVs),organic field effect transistors(OFETs),organic light-emitting diodes(OLEDs)and organic photovoltaic devices(OPVs).However,the realization of controlled growth of two-dimensional organic single crystals is still challenging,which limits the research on its optoelectronic properties and application to high-performance devices.In this thesis,controllable preparation strategies for two-dimensional organic single crystals have been developed,and its spin and charge transport properties have been explored.The main research results are as follows:(1)Large-area two-dimensional organic single crystals of6,13-Bis(triisopropylsilylethynyl)pentacene(TIPS-pentacene)with different thicknesses were grown on the surface of a liquid substrate by adjusting the concentration of the semiconductor solution.Subsequently,the first working single-crystalline organic spin valve was constructed and spin transport characteristics of organic semiconductor(OSC)were studied.Glycerol was chosen as a liquid substrate.The high surface tension together with the high viscosity of glycerol can promote the spreading and fix the position of the solution during evaporation,which was favorable for the production of thin and large-area single crystals.Single crystals of different thicknesses can be obtained by adjusting different solution concentrations.The magnetoresistance(MR)responses of the organic spin valves based on single crystals at different temperatures and thicknesses were investigated to study the spin injection and transport properties.Magnetoresistance value as large as 17% was probed with an intermediate layer thickness of 269 nm.More importantly,spin transport could still be observed in a single crystal of a thickness up to 457 nm,which was much larger than that of polycrystalline thin films.Our research provides a general method to construct single-crystalline organic spin valves and paves the way to probe the intrinsic spin transport properties of organic semiconductors based on single crystals.(2)A two-phase dip-coating strategy was proposed to controllably grow the large-area two-dimensional organic single crystals,and the optoelectronic properties of the two-dimensional organic single crystals were studied.Compared to traditional single-phase dip-coating method,two-phase dip-coating provided a larger surface to volume ratio of the solution,which led to a greater evaporation flux at the liquid–air interface.Therefore,heterogeneous nucleation was more likely to occur,thereby preparing large-area high-quality films.The effects of substrate type,solvent type,solution concentration,pulling speed,and drop amount of organic solution on the morphology of films were systematically studied.Several nanometer ultra-thin and centimeter-scale single crystals were obtained and used as the active layer of the OFETs,showing excellent optoelectronic performance.This work provides a fast and efficient new method for preparing large-area ultra-thin organic single crystals and provides a new idea for the further investigation of the optoelectric properties of the two-dimensional organic single crystals.