Combined DFT and QM/MM Modeling on Multifunctional TADF Sensitizers and Hot-Exciton Emitters via Carborane Triads for Blue Hyperfluorescent OLEDs

Abstract

The scarcity of novel luminogens significantly impedes the advancement of TADF sensitizers and hot exciton emitters, attracting considerable attention for their potential to enhance energy conversion efficiencies in hyperfluorescent OLEDs. In this study, a systematic investigation is employed to design and develop multifunctional materials based on carborane cores through DFT and TD-DFT methods. In pursuit of this objective, 45 carborane triad-type molecules were systematically designed using four donors and two acceptor units. Electronic structure calculations revealed that (i) the singlet, triplet, ΔE ST, and SOC values exhibit an increased trend as the carborane core shifts from ortho to meta to para, while an increase in donor strength on the core leads to a decrease in these values. (ii) Moreover, there is a decrease in reorganization energies, absorption wavelengths, ISC, and RISC rates as the carborane switches from ortho to meta to para while witnessing an increase in donor strength. The QM/MM study reveals that para carborane’s restricted intramolecular motions improve its solid-state aggregation over ortho carborane and solution phases. Interestingly, carborane triads featuring P-DMB and P-BODIPY acceptor units satisfy the desired criteria for multifunctional TADF sensitizers and hot exciton emitters, respectively.