Electronic structures and photophysical properties of carbazole- and thiophene-based organic compounds used as hole-injecting layer for organic light-emitting diodes (OLEDs)

In this study, we have carried out a theoretical study on six organic compounds based on thiophene and carbazole, with the aim of using them as a hole-injecting layer of organic light-emitting diodes (OLEDs). In this study, we have tested two types of structures: D-pi-D for MO1, MO2, MO3, and MO4 compounds and D-pi-A for MO5 and MO6 compounds. The correlation structure-properties of these studied compounds have been proceeded and discussed by analyzing highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), energy gap, polarization effect, atom transition density matrix, absorption, and photoluminescence (PL). This theoretical study, based on density functional theory (DFT)/TPSSTPSS/aug-cc-pVQZ and the integral-equation-formalism polarizable continuum model/Coulomb attenuated method-Becke, 3-parameter, Lee-Yang-Parr (IEFPCM/TD-CAM-B3LYP)/6-31++G(d,p) is consolidated by experimental data for MO1, MO2, and MO4 compounds, allowing the determination of their structural and optoelectronic properties (HOMO, LUMO, gap [Eg], absorption, and emission parameters). The obtained results appear very conclusive and show that the performance of these compounds in terms of luminescence, absorption, and current-voltage (I-V) characteristics of OLED devices make them a promising candidate for the realization of light-emitting diodes.