Study On The Controllable Preparation Of Organic Micro-Nano Composite Structures And Their Optical Characteristics

Compared with traditional inorganic or amorphous materials,organic semiconductor materials have the advantages of precise synthesis,structural diversity,multifunctional integration,and lowcost large-area processing,which can be widely used in various optoelectronic devices and more conducive to the preparation of high-integration and high-performance optoelectronic devices.With higher requirements for miniaturization,integration,and multifunctional features of organic devices,materials consisting of organic multilevel complex micro-nano structures with multifunctional characteristics are increasingly desirable.However,due to the complexity of the self-assembly mechanism of organic semiconductors,there is still a lack of basic research on both controllable construction of multifunctional multilevel micro/nano structures and precise manipulation of optical signals,leading to the difficulties in the preparation of micro-nano photonic devices such as organic waveguides.Therefore,this thesis has focused on the two main scientific issues of the controllable construction of organic low-dimensional composite crystalline structures and the precise manipulation of optical signals,which involve from the manipulation of emission colors,the controllable preparation of complex structures,to the construction of photonic devices.The main research contents are summarized in the following aspects:(1)Based on the charge transfer between the donor and the acceptor,and the good lattice matching and energy balance,we used TBP as the electron donor and TCNB,OFN and TFP as the electron acceptor,respectively,to achieve the controlled preparation of multi-color and multi-mode organic core-shell heterojunction.Firstly,by adjusting the acceptor/donor molar ratio of TBP and TCNB and the ambient temperature,the blue-red core-shell heterojunction and blue-green core-shell heterojunction were prepared in a controllable way,which realized the combination of the fluorescence tunable properties of organic micro-nano crystalline structures and organic heterojunctions.Secondly,the blue-green core-shell heterojunction and the blue-purple-yellow coreshell heterojunction were prepared by TBP and OFN.Finally,a two-dimensional core-shell heterojunction was constructed by using TBP and TFP,systematically investigating their optical waveguide properties.Among them,the optical loss coefficient(R)of the TBP crystal was around0.0129 d B/μm,demonstrating good optical waveguide.It is worth mentioning that both two-color axial core-shell heterostructures and the four-color multi-segment core-shell heterostructures constructed by TBP and TFP exhibit asymmetric waveguide characteristics,and the normalized spectra of the four-color multi-segment core-shell heterostructures show unique spectral modulation effects.When the excited beam was irradiated alternately on the monochromatic segment and the heterojunction,the spectral band presented periodic extension and compression,which fully demonstrated the potential application of the multisegment waveguide heterostructure as an optical filter device.This work can provide a new strategy for the preparation of multi-color and multi-mode organic core-shell heterojunctions but also demonstrate the universality of TBP as the donor material for the construction of organic heterojunctions.(2)Based on the fact that TBP and TCNB could achieve one-dimensional blue-red core-shell heterojunction in the previous stage,the regulation of blue-red core-shell heterojunction to blue-red branch heterojunction was successfully achieved by using the method of adding the poor solvent,that is,adding the inferior solvent ethanol to the good solvent dichloroethane without changing the two materials of TBP as the donor and TCNB as the acceptor.The significant difference in the solubility of TBP and TBP-TCNB in the ethanol-dichloroethane mixture can result in their sequential nucleation and crystallization,and the faster crystallization rate caused by the alcohol antisolvent facilitate the possibility of fabricating another organic crystal on the surface of one organic crystal.This is the key factor that can realize the transition from the organic core-shell heterojunction to the organic branch heterojunction.This simple solution method with the addition of the poor solvent can ingeniously realize the regulation of the organic core-shell heterojunction to the organic branch heterojunction,which can provide a new idea for the development of organic low-dimensional composite structures in the later stage.(3)The dependence of the crystalline morphologies of TCNB on solvent was systematically investigated.It was found that the hyperbranched array structure of TCNB crystals can be prepared in both dichloromethane and dichloroethane solvents.Owing to the drawback that TCNB itself does not emit light in the visible wavelength range,we doped TBP,F8 BT,1,2-Ph2 py and other materials into TCNB via the doping method,and achieved the goal of both secondary branching and luminescence in the TBP doping range of 5%-10%.Among them,the doped F8 BT grew along the hyperbranched structure and emitted green light.Meanwhile,the red complex generated by TBP and TCNB was produced on one side of the hyperbranched structure,thus generating the organic heterostructure based on the inherent branched structures of TCNB.This kind of composite micronano crystals based on hyperbranched structures can provide an important material basis for highperformance organic photonic devices,which is expected to realize the miniaturization,integration and multi-functional application of organic photonic devices.