Recent advancements in phenanthroline-derived TADF materials for efficient organic light-emitting devices

This review mainly focuses on phenanthroline-based TADF emitters, highlighting their molecular design, photophysical properties, and applications in high-efficiency OLEDs. Phenanthroline serves as a rigid, planar, and electron-deficient acceptor core, enabling small singlet-triplet energy gaps (ΔE_ST) and efficient reverse intersystem crossing (RISC). Modifications to these materials primarily aim to tune electronic and steric properties through strategies such as substituent engineering, donor-acceptor pair optimization, core fusion or π-extension, and positional isomerism. These approaches control HOMO-LUMO overlap, energy gap (ΔE_ST) and charge-transfer characteristics, resulting in high photoluminescence quantum yields (PLQYs) and enhanced external quantum efficiencies (EQEs). This review systematically discusses these design strategies, structure-property relationships, and recent advances in orange to red TADF emission, highlighting the potential of phenanthroline-based materials for next-generation organic light-emitting devices.