Theoretical Study On The Electronic Structures And Photophysical Properties Of Containing N-heteroaryl Carbazole And Anthracene Derivatives

Organic light-emitting diodes (OLED) have made remarkable development in bothacademic research and commercial applications around the world. Due to their characteristiclow driving voltage, high brightness, rapid response and self-emitting properties, OLED weresuccessfully applied in mobile phones, car stereos, digital cameras and white solid-statelighting. However, the more extensive application of OLEDs in large-area and flexibledevices was limited by the factors of high cost, efficiency, and lifetime. To solve theseproblems, the modifications of different linkage matterns and electron-acceptors were madeon the structure of experimental compounds. The electronic structure and properties ofsynthetic compounds and the designed molecules were investigated by quantum chemistrycalculations.First, to provide a profound view on structure-property relationships, new linear-shapedcounterparts have been designed based on the existing molecular composition and the linkageat para-position (p-type molecules). A series of studies about the influence of the linkagemode on optical and electronic properties of these carbazole derivatives have carried out viadensity functional theory (DFT) and time-dependent density functional theory (TDDFT)calculations. The geometric and the electronic structure of these molecules in the groundstates, ions states, and lowest triplet states have been calculated especially focusing on theanalysis of HOMOs, LUMOs, energy gaps, triplet energies, ionization potentials, electronaffinities, reorganization energies, triplet exciton-formation fraction, and absorption spectra.These optoelectronic properties can be effectively tuned by the chemical modifications ofdifferent linkage pattern. The good coordination between our calculated results and theavailable experimental data has been observed. The study reveals that the designed p-typemolecules show great promise as new high-performance red host materials with large tripletenergy, narrow energy gap, good electron and hole transport properties, and high tripletexciton-formation fraction.Second, the molecular architecture based on covalently bonded carbazole and anthracenemoieties (p-DAC) have great potential for deep-blue organic light-emitting diodes (OLEDs).To improve the electronic transport abilities, s-DAC, s-BMA, and s-DATPSO were designedby linking anthrancene as the end-group and core units with thiophene chain as π-conjugatedbridge. The core segments include carbazole, benzimidazole, and s,s-dioxydibenzothiophene.A systematic investigation of the electronic structure and optical properties into them havecarried out using the density functional theory. The photoelectronic properties includingHOMO, LUMO, IP, and EA values can be adjusted by prolonged π-conjugated chain and thedifferent electron-acceptor strength of core units. To further understand the effect of topologystructure on the electronic properties, p-DCA molecule was designed and compared withp-DAC. Their structure differences were that the anthrancene moiety is located in themolecular structure centre or periphery. As shown by the results, it indicates the topologystructure difference hardly influence these photophysical properties. p-DCA can be predicted as a promising blue electroluminescent material.