Precise Construction And Photonic Research Of Organic Deformed Crystalline Low-dimensional Structures

Organic semiconductor crystal materials have extensive application prospects in the field of optoelectronics,including organic light-emitting devices,organic field-effect transitions,organic solid-state lasers and circuits,due to their excellent properties,such as rich molecular structures,low defect density,regular morphology,ultrafast nonlinear response.To meet the ever-increasing practical demand for miniaturization and integration of nanostructures,organic crystalline hierarchical low-dimensional micro/nanostructures have drawn much attention in recent years.However,owing to the difficulty in controlling the nucleation process of molecules,it remains a huge challenge to reasonably construct hierarchical low-dimensional crystals with specific morphologies at micro/nanoscale and regulate their growth dynamics.Therefore,this thesis focuses on the controllable construction of organic crystalline deformed low-dimensional structures and the precise manipulation of optical signals.Starting from the design of molecular structure and regulation of self-assembly behavior,a series of controllable synthesis schemes are developed to systematically study the growth mechanism and photonics properties of the prepared organic deformed low-dimensional structures.The specific research contents are as follows:1.Through a typical solution self-assembly method,the one-dimensional(1D)crystalline deformed microrods formed by molecular rearrangement-based twinning deformation process is controllable fabricated,providing a novel growth mode for 1D axial microstructures.In detail,the continuous increased temperature of quartz substrate weakens the bonding force between the(001)planes(the densely packed crystal surface of atom),resulting in a large bending angle of ～50° in the 1D axial microstructure based on a diffusion free manner.At the same time,the integrity of crystal is preserved.The bending angle is basically consistent with the dihedral angle of 50.8° between the(001)and(101)plane,which is consistent with the statistical results of the actual bending angles of a large number of deformed microstructures.The work provides a fundamental microstructure for the precise construction of desirable organic hierarchical low dimensional micro/nanostructures.2.On the basis of previous work,this chapter combines a synergistic growth mode of molecular rearrangement-based twinning deformation and lattice matching-based epitaxial growth processes,by taking advantage of the dislocation stress field-impurity interaction that solute molecules deposit preferentially along the dislocation line,achieving the oriented self-assembly process of branch organic microstructures with definite branch position.The growth mechanism of these branch crystals with an angle of140° is attribute to the low lattice mismatching ratio(η = 4.8%)between the(110)and(111)planes.The photons within twinned microrods are able to contact the twinning surface during transmission.On this basis,an asymmetry optical waveguide in 1D single crystal could be achieved,which significantly constructs an optical logic gate with an ON/OFF ratio of ≈ 27.4.At the same time,the optical logic gate operation of multiple input/output channels is realized on the basis of the asymmetric optical waveguide behaviors within the branch structures.This work opens up a completely-new avenues for the controllable construction of organic crystalline hierarchical low dimensional structures and their potential application at micro/nanoscale.3.Based on the crystal growth mechanism demonstrated in the above work,the electron acceptor molecule 2,4,6-trimethylbenzene-1,3,5-tricarbonitrile(TBT)and a series of organic electron donor π-conjugated molecules are selected as the construction units of organic hierarchical low-dimensional structures.Through the growth mechanism that from slipping to twinning and hierarchical slipping and hierarchical twinning processes within organic 1D single crystals,the slipped microstructures controlled by dynamics and the twined microstructures controlled by thermodynamics are constructed.Furthermore,by changing the organic donor molecules,the hierarchical deformed crystalline low-dimensional microstructures with different angles(72.76°-85.48°)are able to be accurately constructed.This work is helpful to guide the design and synthesis of organic crystalline hierarchical low-dimensional micro/nanostructures.