Three- and Four-Coordinate, Boron-Based, Thermally Activated Delayed Fluorescent Emitters

Recent developments in purely organic-material-based thermally activated delayed fluorescence (TADF) emitters are helping to make them suitable for commercial applications in the near future. In spite of their high external quantum efficiencies, the broad emission spectra and short device lifetimes are the main barriers to using TADF emitters. Among the classes of materials, boron-embedded polycyclic aromatic compounds have shown potential as TADF emitters that overcome the technical issues. In particular, highly efficient boron-based TADF emitters with the advantage of a narrowband emission spectrum have been reported recently relying on the concept of a multi-resonance effect. Hence, boron TADF emitters have the potential to become next-generation emitters. Based on the future scope of the boron-based TADF emitters (especially in development of blue TADF emitters), three- and four-coordinate boron TADF emitters are reviewed. Additionally, future prospects of boron-based TADF emitters are discussed to resolve the issues of low efficiency and short lifetimes of blue emitters.