Theoretical Studies On The Charge Transport Properties Of Chalcogen-containing Optoelectronic Materials

Organic optoelectronic materials have been widely explored as building blocks invarious organic electronic devices such as organic light-emitting diodes, organicfield-effect transistors and organic photovoltaic cells. In comparison to traditionalinorganic materials, they attract more and more attention from both academic andindustrial interest due to their numerous advantages such as low cost, easy fabrication,light weight, and large-area production. The performances of electronic devicesdepend crucially on the charge transport characteristics of the carries. Thus, it is ofgreat importantance to understand the charge transfer property of organicoptoelectronic materials from the microscopic point of view. With rapid developmentof the technology of computer and the updating of quantum chemical method,theoretical calculation is becoming a powerful tool to studing the relationship betweenmicroscopic structure of materials and performances. By imploying Marcus electrontransfer theory coupled with an incoherent charge hopping and diffusion model, wehave investigated the charge transport properties of two types of chalcogen-containingorganic optoelectronic materials.Chalcogen-containing organic semiconductors have been proved to be one of themost valuable semiconductors for use in OFETs and OPVs. Heteroannulation hasbecome an effective way to generate non-bonding intermolecular interactions,including S…S, Se…Se, S…H and so on, which leads to the increase of transferintegral and decrease of intermolecular distance and thus enhanced charge transportproperties. In the first part of this thesis, we have summarized the research advances of charge transfer property for organic optoelectronic materials and choosen twochalcogen-containing organic optoelectronic materials system for the object of ourstudy.Section2describes density functional theory and quantum chemical approaches tocompute the parametes that govern the intermolecular charge transfer process, such ashole and electron reorganization energy, molecular ionization potential, electronaffinity, transfer integral, drift mobility and anisotropic mobility.We will focus on the substitutions effect chalcogen atoms on the electronicstructure and effect of chalcogen-chalcogen interactions on the charge transportproperties. We try to establish structure-property relationships and shed light on thedesign of chalcogen-containing high charge mobility materials. Our work mainlyincludes two aspects as follows：1. The electronic and charge transport properties of a series of fused aromaticchalcogenophene compounds are investigated via quantum chemical calculations. Togain a better understanding of the physical properties of chalcogenophene, theheteroatom, molecular topological and substitution effects have been taken intoaccount. Through a comparative study, the molecular ionization potentials, electronaffinities as well as the internal reorganization energies of chalcogenophenes areanalyzed. Compared with the angular-shape with4ring fused, the reorganizationenergy of linear-shaped with4ring fused is minimum. The intermolecular interactionthrough close chalcogen-chalcogen interactions and C-H… π interactions arerecognized in relation to the charge transfer integrals.2. The electronic and charge transport properties of five ocathio[8]circulenecompounds are investigated via quantum chemical calculations. The results indicatethat the substitution of selenium atom could reduce both reorganization energy forhole and electron, especially for electron reorganization energy. The introduction offour t-Bus can slightly affect the reorganization energy, but largely change thepacking motifs of such system. Our angular resolution mobility study suggests thetransport properties of ocathio[8]circulene have the anisotropic feature ofcharacterizes.