Oligothiophene Nt, (n = 3,4,6) Series Of Derivatives Of Carrier Transport And Spectroscopic Properties Of The Theoretical Research

Oligothiophenes and their derivatives were widely used as a kind of activeπ-conjungated materials in organic electroluminescence devices (OLEDs), for their good stabilities among the process of pre-and post-doping, easier to be modified structures and controlled photoelectric properties, the traditional linear systems have been easied to extend to higher dimensionalities and new topologies, thus they showed well stable and novel physical chemistry properties and exhibited good future of their application. Understanding the relationships between the geometris and excited state properties is very important to design new photoelectic materials and tune their photoelectronic properties. Various oligothiophene derivatives with particular electrical properties have been investigated by a lot of experimental groups, but the related theoretical studies is rarely reported. Therefore, summerizing the relationship between the structures and properties of existing oligothiophenes and their derivatives has significant academic significant and potential induastral applications. It can also open a door to design novel oligothiophenes as luminescence materials and electron or hole transport materials in OLEDs.Three types of thiophene derivatives were designed as luminescene materials or carrier transporting materials. To better understand the tri-aryl end-caps effect on electronic and spectra properties, tri-aryl amine and tri-aryl boron end-capped terthiophene derivatives were investigated. The second series are biphenyl substituted tetrathiophene and their perfluoro derivatives. The third series are sexithiophene and their thiothiophene derivatives, as well as structural difference between theirα-position andβ-position compounds. Quantum chemistry methods of ab initio Hartree Fock (HF) and Density Functional Theory (DFT) were carried out to calculate the oligothiophenes and their derivatives. Based on the optimized geometries of compounds in ground and excited state, Time Dependent Density Functional Theory (TDDFT) and Configuration Interaction at Single excition level (CIS) were employed to calculate the absorption and emission spectrum, and to study the relationship between electronic transition and spectral properties.According to the results, in comparison with prototype molecule, the geometries and electronical properties of designed oligothiophene derivatives show appreciable changes. Compared to terthiophene, the IPs of three terthiophene derivatives decrease sharply, the EAs increase quickly, the carrier transport properties have obviously improved; the absorption and emission spectrum exhibited bathochromic shift, and the wavelength extended from weak blue light of trethiophene to strong yellow and green scopes. Tri-aryl end-capped terthiophene derivatives may be as bi-funtional OLEDs materials. The results also shown that introducing phenyl rings into oligothiophene backbones is not only improve the oscillator strength of absorption and emission spectrum, but tune the luminescence wavelength of phenl-thiophene co-oligomers in blue light scope and improve their optical properties; their perfluoro substituted derivatives can tune the emitting scope and improve carrier transport properties under keeping conjugated degree. The results of the third type sexithiophene and its derivatives indicated that thieno-sexithiophene decreases the conjugated degree and strengthens the co-planar of sexithiophene, which makes the emitting wavelength in blue light scope and possibely improves their charge transport proeprties. In conclusion, Substituted on oligothiophene or changing connecting mode can tune emitting wavelength and improve carrier transport properties, and also predict the electronic and spectral properties of other oligothiophene compounds.