Design,Synthesis And Application Of Organic Optoelectronic Materials Modified By Heteroatoms

The design and preparation of new organic optoelectronic materials are crucial to the development of organic optoelectronics.By introducing functional groups with special electronic effects into organic conjugated molecules,their photoelectric performance can be effectively modulated.The functional group modified by heteroatoms can be used as an electron donor or an electron acceptor.By combining the electron donor and acceptor unit,the intramolecular charge transfer can be effectively improved,thereby regulating the photoelectric properties of the materials.In addition,the introduction of heteroatoms with lone pairs provides n orbitals,which makes ~1(n,?*)?~3(?,?*)or~1(?,?*)?~3(n,?*)transition possible.This can improve the intersystem transition process from singlet state(S_n)to triplet state(T_n).More importantly,heteroatoms with high electronegativity can form multiple intramolecular and intermolecular interactions including hydrogen bonds,which provides a more rigid environment for molecules and effectively suppresses non-radiative transitions.This improves luminescent efficiency and prolongs emission lifetime.In view of the above characteristics of heteroatoms,we designed and synthesized a series of compounds modified by heteroatoms,and investigated their photophysical and excited state properties.Then,we explored the practical application of such materials in optoelectronic field.The details can be divided into the following three parts:1)We designed and synthesized the optoelectronic material TBZ-tbucz based on benzothiadiazole and tert-butylcarbazole.We found that it exhibits the interesting mechanochromic properties.After mechanical grinding,the photoluminescence spectra of TBZ-tbucz shift from 550 nm to 610 nm.By studying the single crystal structures,it can be found that the TBZ-tbucz molecules are arranged in a misaligned?-?stacking mode,and the interaction among the molecules is weak.Upon applying the external forces,the configuration of the molecule easily changes,so that the photophysical properties will be also tuned.In view of the high fluorescence efficiency of TBZ-tbucz,we applied it to organic light-emitting diodes,and achieved the electroluminescence at 560 nm and 601 nm.The different electroluminescence from one material can provide a new development direction for organic optoelectronic materials and devices.2)We designed and synthesized a series of compounds(2-t-BU-PPMT,3-t-BU-PPMT,and 4-t-BU-PPMT)by combining tert-butylcarbazole and benzophenone.The combination of aromatic carbonyl and tert-butylcarbazole units promotes the intramolecular charge transfer.Utilizing the solvation effect,we can achieve nearly full-color emission of 4-t-BU-PPMT from blue to orange.The D-?-A structure separates the electron cloud of the compound.All of the three compounds have small difference between singlet and triplet energy levels.The enhanced reverse intersystem crossing promotes the three compounds to achieve thermally activated delayed fluorescence.We have verified this property through emission lifetimes and spectra from 200 to 300 K.All three compounds exhibit good solubility,thermal stability and film-forming properties,which is conducive to their application in organic light-emitting diodes.The maximum current efficiency of electroluminescent devices based on 2-t-BU-PPMT is 20.28 cd/A and the maximum external quantum efficiency is 10.2%,which can be attributed to its ultra-high quantum efficiency of 97%.These shows that it has promising application in organic electroluminescent devices.3)We designed and synthesized a series of oxo borate compounds(DBOB,2FDBOB,3FDBOB,and 4FDBOB).All of these compounds exhibit phosphorescent properties with ultra-long emission lifetime.As the substitution sites of fluorine atoms change,the lifetimes of these phosphorescent materials increase from 863 ms(DBOB)to 1366 ms(4FDBOB).Through crystal analysis,the introduction of highly electronegative fluorine atoms has established multiple intermolecular interactions(CH···O and CH···F).These interactions have an anchoring effect on the molecules,which limits the movement of the molecules to a certain extent.Combining experimental and theoretical analysis,we believe that the reduced non-radiative transition is the main reason for the prolonged phosphorescencent lifetime.In view of ultra-long phosphorescence lifetime,we applied4FDBOB to data anti-counterfeiting and achieved a good application result.