Pure Hydrocarbon Hosts for ≈100% Exciton Harvesting in Both Phosphorescent and Fluorescent Light-Emitting Devices

Two novel pure hydrocarbon compounds, SF33 and SF34, are designed with high triplet energies and stabilities. The efficiency of an SF34/FIrpic‐based device is as high as 22.0%. Moreover, SF33 and SF34 are also used as hosts for thermally activated delayed fluorescence organic light‐emitting diodes and achieve external quantum efficiencies in excess of 20.8% and 22.3%, respectively. The pure hydrocarbon host shows a much longer device lifetime than the traditional host 4,4′‐di(N‐carbazolyl)biphenyl.