Manipulation Of Aggregation Structures And Optical Properties Of Organic Luminescent Cocrystals

Organic functional materials have exhibited broad application prospects in the fields of organic light-emitting diodes(OLEDs),organic solid-state lasers(OSSLs),and organic field effect transistors(OFETs),because they have unique electronic structures and outstanding optoelectronic properties.For organic crystals,the aggregation structures are dominant factors in determining the photoelectric properties.The organic cocrystals which are assembly by multiple components in an orderly manner have special molecular packing patterns and aggregation structures.The multi-component synergistic effects make the cocrystals not only retain the inherent properties of a single component,but also exhibit more novel macro-photoelectric properties.This makes organic luminescent cocrystals become the frontier hotspot of international research.The thesis takes divinylanthracene as the study object.By introducing conformers or changing the crystallization conditions,we obtained new luminescent crystal materials with different optical properties and clarified the structure-property relationship.The main contents are as follows:1.We prepare orange emission BP3VA-BFC cocrystals with rod structure through the solvent evaporation method.BP3VA-BFC cocrystal exhibit different aggregation structures and optical properties compared with BP3 VA crystals.Both BP3VA-BFC cocrystal and BP3 VA crystal have certain polarization properties,while the polarization angle is different when the out-coupling emission intensity reaches the maximum.For BP3 VA crystals,the emission intensity is the highest when the orientation is about 65° and 245°,while in BP3VA-BFC crystals,the emission intensity is the highest when the orientation is about 19° and 199°.The polarization contrast of BP3 VA crystals is 0.25,and polarization contrast of BP3VA-BFC crystals is 0.26.We have carried out structure analysis and theoretical calculations,and the results show that transition dipole moments exhibit a zigzag arrangement and a cross arrangement on the emitting crystal planes of BP3 VA crystals and BP3VA-BFC crystals,respectively,which greatly weakens the anisotropy of emission.This work enriches the luminescent cocrystals system and makes a certain contribution to understanding the relationship between structures and properties.2.Two types of cocrystal polymorphs(C1 and C2)of BP3VA-FIB system are obtained by the solvent evaporation method,in which C1 has 2D sheet structure,however C2 has 1D needle structure.Two types of cocrystal polymorphs exhibit different aggregated structures and optical properties.C1 exhibits anisotropic optical waveguide property and remarkable polarization.The reason for the asymmetry of light propagation is the anisotropic organic molecular packing in different crystal planes for C1.Furthermore,the emission intensity showed very strong dependence on the angle of polarization.The out-coupling emission intensity reaches the maximum when the polarization angles are about 80° and 260°,which reveal that the C1 crystals couple with the laser electrical field most effectively in this orientation.The minimum of emission intensity appears when the orientation(??170° or 350°)are approximately perpendicular to the polarization direction of the maximum emission intensity.In comparison,C2 only exhibits quasi-one-dimensional(1D)optical waveguide property.The reason for different optical properties of two cocrystals is elucidated and the structure-property relationship is investigated through the combination of crystal structure analysis and theoretical calculation.The work has certain guiding significance for targeted design of functional cocrystal materials.