Theoretical Study On The Photophysical And Charge Transport Properties Of Biheterocyclic Compounds

The organic optoelectronic materials,particularly organic semiconductors have long been received significant attention due to its low-cost,easy production,ductile,lightweight,high flexibility and environment benignity.Consequently,a number of excellent organic semiconductor materials(OSMs)have been developed and employed in various fields,including organic field-effect transistors(OFET),organic light-emitting diodes(OLED),organic photovoltaic cells(OPV)and etc.Recently,the introduction of heterocyclic in semiconductor materials was found to could sensitively influence their optoelectronic properties.In this thesis,we mainly focus on how the heterocyclic tunes the electronic structures,spectral and photophysical properties along with carrier transport abilities by applying the quantum chemistry method with the aim of finding good balance between photophysical and carrier transport efficiencies.In this work,a comparative theoretical(using density functional theory(DFT))investigation on photophysical and charge transport properties of three biheterocyclic derivatives,5,5-bis(2,2-diphenylvinyl)-bithiophene(BDPV2T,1),5,5-bis(2,2-diphenylvinyl)-bifuran(2)and 5,5-bis(2,2-diphenylvinyl)-bipyrrole(3)was investigated.The calculated geometrical and electronic structures demonstrate almost similar structures and orbital distributions.The absorption and emission spectra show a slight blue shift from compound 1 to 3 and their radiative rates(kr)are almost the same.While the differences in geometrical change from the excited state to ground state lead to their different nonradiative rates(knr)and thus distinct fluorescence quantum yields.Furthermore,in order to discuss the influence of heteroatom substituents on the carrier transport property,the hole and electron mobilities were also evaluated based on experimental and predicted crystal structures.It is found that the different crystal structures of 2 and 3 with 1 lead to their distinct intermolecular orbital overlaps and electronic couplings and thus the carrier transport abilities.