Theoretical investigations on electronic structures and photophysical properties of N-heteroaryl carbazole derivatives as host materials

Abstract

The carbazole-endcapped host molecules with tailoring different heteroaryl core and meta-position linkage mode have great potential on phosphorescent organic light-emitting diodes. To provide a profound view on structure–property relationships, new linear-shaped counterparts have been designed based on the existing molecular composition and the linkage at para-position (p-type molecules). A series of studies about the influence of the linkage mode on optical and electronic properties of these carbazole derivatives have carried out via density functional theory and time-dependent density functional theory calculations. The geometric and the electronic structure of these molecules in the ground states, ions states, and lowest triplet states have been calculated especially focusing on the analysis of highest occupied molecular orbitals, lowest unoccupied molecular orbitals, energy gaps, triplet energies, ionization potentials, electron affinities, reorganization energies, triplet exciton-formation fraction, and absorption spectra. These optoelectronic properties can be effectively tuned by the chemical modifications of different linkage pattern. The good coordination between our calculated results and the available experimental data has been observed. The study reveals that the designed p-type molecules show great promise as new high-performance red host materials with large triplet energy, narrow energy gap, good electron and hole-transport properties, and high triplet exciton-formation fraction.