The field of organic light-emitting devices (OLEDs) has undergone a remarkable journey since its discovery by Tang and VanSlyke with an alternation of utilizing fluorescence and phosphorescence as the emitting vehicle. The latest generation of thermally activated delayed fluorescence (TADF) materials harvest triplet excited states back into the singlet manifold. This booming field has yielded a large array of new compounds as both emitters and hosts. This review is limited to TADF emitters utilizing at least one carbazole unit as a donor and organized according to the various acceptor building blocks such as cyanophenyl, pyridine, biphenyls, anthraquinone, phenyl(pyridine-2-yl)methanone, benzophenone, xanthon, sulfones, triazines, benzils, dicyanopyrazines, diazatriphenylene, and others. A survey of carbazole-containing host materials follows. Density functional theory (DFT) has carved out a significant role in allowing the theoretical prediction of ground state properties for materials applied in OLED technology. Time-dependent DFT extends the reach to model excited state properties important to rationalize the light-output in OLED technology. For TADF, two fundamental factors are of interest: significant separation of frontier molecular orbitals and minimal singlet–triplet energy gap (ΔE_ST). In this review, the utilization of DFT calculations to optimize geometries for the visualization of frontier molecular orbital separation was surveyed to find that the B3LYP/6-31G(d) level of theory is the overwhelmingly used approach. In addition, we review the more in-depth approaches to utilizing DFT and time-dependent DFT (TD-DFT) with optimized percentage Hartree–Fock (OHF) and long-range corrected hybrid functionals, tuning procedures and others in an attempt to best quantify the size of ΔE_ST as well as the nature of the triplet state as locally excited state (LE) and charge-transfer state (CT).

Tetrahydropyrene and pyrene have been functionalized in their 2,7-positions with carbazole and 3,6-di-tert-butylcarbazole groups, and the properties of these new compounds are compared to analogous carbazole and 3,6-di-tert-butylcarbazole derivatives of benzene and biphenyl using X-ray crystallography, UV-vis absorption and fluorescence spectroscopy, electrochemistry, and quantum-chemical calculations. The absorption spectra are similar to those of their biphenyl-bridged analogues, although TD-DFT calculations indicate a different description of the excited states in the pyrene case, with the lowest observed absorption no longer corresponding to the S₀ → S₁ transition. The 3,6-di-tert-butylcarbazole compounds show reversible electrochemical oxidations; the benzene, biphenyl, tetrahydropyrene, or pyrene bridging groups have little impact on the first oxidation potential. Bilayer organic light-emitting diodes incorporating the tetrahydropyrene and pyrene derivatives as emitters show deep-blue electroluminescence.

We report a first investigation of two new isomer-pure thieno[f,f′]bis[1]benzothiophenes, i.e.syn and anti with respect to the orientation of the thiophenes along the long axis of the molecule, applied as organic semiconductors in organic field-effect transistors. The field-effect mobility of both regioisomers is substantial and reaches up to 0.12 cm² V⁻¹ s⁻¹, a value that is at most one order of magnitude lower than the best known organic transistors based on silicon dioxide gate insulators.