Exceptional class of thermally activated delayed fluorescent emitters that display pure blue, near-IR, circularly polarized luminescence and multifunctional behaviour for highly efficient and stable OLEDs

Thermally activated delayed fluorescence (TADF) emitters with the ability to harvest both electro-generated singlet and triplet excitons have resulted in faster radiative decay, saturated color purity, a high photoluminescence quantum yield (PLQY), and the suppression of efficiency roll-off for efficient OLEDs. Considering these advantages, some exceptional types of TADF materials, that show pure blue emission, near-infrared (NIR) emission, circularly polarized luminescence (CPL), aggregation induced emission (AIE) and emitters that show multifunctional behavior, have recently been developed for highly efficient and stable OLEDs. In particular, these emitters have probably emerged as part of the design strategy to realize high PLQY, high color purity, circularly polarized light and have resolved the issues of long-term device stability. This review highlights and collates various key properties of these new-generation emitters by covering the experimental and theoretical aspects of model TADF emitters. This review also discusses the strategic material design principles, conceptual insights, and photophysical properties with structure-functionality that can influence their energy gap, triplet-to-singlet up-conversion, and ultimately the OLED performances in some of these materials.