Molecular Configuration Fixation with C–H···F Hydrogen Bonding for Thermally Activated Delayed Fluorescence Acceleration

Organic light-emitting diodes (OLEDs) have been commercially applied in flat-panel displays because of their high efficiency, low cost, and flexibility. Generally, triplet excitons are typically non-emissive, lower in energy, and longer lived than singlet ones, and could not be effectively used in traditional fluorescent OLEDs. An alternative emission mechanism named thermally activated delayed fluorescence (TADF) has been extensively illustrated and can realize theoretically 100% internal quantum efficiency without involving noble-metal complexes. Nevertheless, the increase of reverse intersystem crossing efficiency might lead to the decrease of singlet radiation, thus greatly affect the optoelectronic performance of OLED devices. Here, we demonstrated a highly twisted multi-carbazolyl compound with both intra- and inter-molecular hydrogen bonds to fix the excited-state configurations, aiming to establish multiple triplet-to-singlet conversion channels for high-efficiency TADF OLEDs.