Achieving Efficient Organic Room-Temperature Phosphorescence through Acceptor Dendronization.

Organic room-temperature phosphorescence (RTP) materials hold significant promise for applications in optoelectronics, information security, and bioimaging. Recently, significant progress has been made in RTP materials and vacuum-deposited organic light-emitting diode (OLED) devices. However, the performance of solution-processed OLEDs is seriously lagging behind due to the lack of RTP molecular strategies that balance exciton stability and solution processability at the single-molecule scale. In this work, we propose an acceptor dendronization strategy for designing RTP materials and successfully achieving highly efficient and stable RTP emissions. This strategy can simultaneously enhance the various processes involved in RTP emission at the single-molecule level: increase the intersystem crossing channels, enhance the spin-orbit coupling constants between T and S, and suppress molecular motion. Consequently, it promotes intersystem crossing and triplet radiative transition while inhibiting nonradiative transition, thereby efficiently enhancing RTP emission. A proof-of-concept acceptor-dendronized dendrimer exhibits long phosphorescence lifetimes in the millisecond range in ambient solution and near 100% photoluminescent quantum yields in the doped films. This is the first reported RTP dendrimer to date. An OLED fabricated using this dendrimer in a sky-blue emission achieves an external quantum efficiency of 25.1%, which represents the state-of-the-art efficiency based on solution-processed RTP-OLEDs to date. Our findings offer definitive guidelines for the molecular engineering of RTP materials and pave the way for innovative RTP systems in diverse optoelectronic applications.