Studies On Ultrafast Spectroscopy Of D-?-A Style Organic Photoelectric Molecules

Human live in a highly informative society,and the modern communications and information technology are also rapidly developing.In this context,a variety of new materials are synthesis as requirements.Among them,the organic photoelectric materials are especially important.The rapid update of organic photoelectric materials promotes the development of modern information technology industry.Therefore,it is very important to study the the organic photoelectric materials from many aspects.For example,materials synthesis,light emitting mechanism,the regulation of light emitting and so on.There are many research groups in the world who have made great efforts to explore the organic photoelectric materials in the fields of physics,chemistry,materials and electronics,and have made many remarkable achievements.Organic compound materials with donor-accepor structure is one of the most widely used organic photoelectric materials.Though studying the photo-physical properties of excited molecule could help researchers understand the charge transfer process,and further study the relaxing mechanism of organic photoelectric compounds.This is benefit to broaden the application of organic photoelectric materials.Moreover,these research results are beneficial for people to design and synthesize new organic optoelectronic compound materials.In this paper,we investigate the ultrufast spectra of a series of D-?-A style organic photoelectric compounds which are consist of triphenylamine(TPA)as electron acceptor unit,?-diketone and its derivatives(?-diketones difluorboron complexes)as electorn acceptor group basing on the pump-prob technique.And discusse the influence of the electron acceptor units number on the photophysical properties of these compounds.In addition,we also study the ultrufast spectra of two organic photoelectric compounds which comprising of difluoroboron b-diketonate complexes as electron accepto units,tert-butyl carbazole and carbazole as electron donor units,respectively.We discuss the role of tert-butyl on the linear and nonlinear photophysical properties of this kind of organic photoelectric compounds.At last,we study the ultrafast spectroscopy of the acceptor-type organic optoelectronic material TPATCN which is composed of TPA as electron donor unit and diphenylfumaronitril(DBFN)as electron acceptor moiety in both mono-dispersed and aggregated state on the film.And explore the solvent effect on the intramolecular electron charge progress.The research results are as follows:1.Three push-pull chromophores comprising of a TPA as electron donor moiety and functionalized different numbers of ?-diketones as electron acceptor units are studied by time resolved spectroscopic techniques.The time-correlated single-photon counting(TCSPC)data which is used to measure the lifetime of emission show that the increasing of electron acceptor unit number accelerates photoluminescence(PL)relaxation rate.Transient spectra(TA)data show that intramolecular charge transfer(ICT)takes place from TPA units to ?-diketones units after photoexcitation.Singular value decomposition(SVD)result show TA spectra consist of three components.Global analysis combined with SVD clarified that: the increasing of electron acceptor prolongs the generation process of ICT state(component I)and accelerates the excited molecule reorganization(component II)process and the relaxation process of transient species from ICT state to ground(component III).In addition,the solvent cage effect results in redshift of stimulated emission peak in the TA spectra after photoexcitation.This shift lifetime gradually shortens owing to the variance of electron acceptor unit number.The final results provide a fundamental understanding of electron acceptor number related ICT state dynamics of multibranched push-pull chromophores based on TPA functionalized ?-diketones.2.We further study the influence of electronic acceptor unit number on the excited state properties of two push-pull compounds,which are comprised of TPA(electron donor units)and functionalized ?-diketones difluorboron complexes(electron acceptor units)by many spectroscopies.We find that the photoluminescence(PL)intensity would enhance with the number of electron acceptor unit number.Transient absorption data shows that intramolecular charge transfer(ICT)process really exists in the two molecules after photoexcitation and this process would be prolonged through increasing the electron acceptor unit number,which would be responsible for the improvement of PL property.On the one hand,the number of transient species from ICT state to ground state would increase,which leads to the enhancement of photoluminescence.On the other hand,the loss of transient species that directly go back to the ground state from initial excited state would decrease.Finally,the 3B with three acceptor units exhibit a better photoluminescence property in comparison with that of 1B with one acceptor unit.3.We compare the linear and nonlinear optical property of two pull-push chromophores,which are composed of difluoroboron ?-diketonate as electron unit functionalized with carbazole and tert-butyl carbazole as electron acceptor unit,respectively.The role of tert-butyl in chromosphere has been discussed in detail.We find that the tert-butyl unit would lead to the absorption and fluorescence peak red shift and accelerate the fluorescence relaxation rate of chromophores.The TA data confirms that the ICT state exist in the photo-excitation relaxation process.The introduction of tert-butyl unit would not change the ICT dynamic mechanism of compounds,but it accelerates the dynamic rate of ICT generation and relaxation process.Moreover,the tert-butyl unit would affect obviously the two-photon optical property of chromophore according to the Z-scan test.These results are beneficial for people to understand the optical properties of push-pull chromophores and further design the novel oligomers.4.We study the ultrafast spectroscopy of the acceptor-type organic optoelectronic material TPATCN which is composed of triphenylamine(TPA)as electron donor unit and diphenylfumaronitril(DBFN)as electron acceptor moiety in both mono-dispersed and aggregated state on the film.We find that intramolecular charge transfer(ICT)process exists in the mono-disperse TPATCN molecule,and the corresponding transfer velocity would be accelerated by solvent polarity.Meanwhile,the energy would transfer from excited TPATCN to the around polar solvent molecules through solvent cage effect based on dipole-dipole interaction.Considering the application of TPATCN in the field of organic light emitting diodes(OLEDs),we also study photo-excitation property of TPATCN in the aggregated state.These are banifical for people to understand the photophysical mechanism of organic optoelectronic compounds and provide theoretical basis for future researchers in the synthesis of new materials and designs novel ophotoelectric devices.