Polymer-Sensitized Hybrid Design Strategy for High-Efficiency Blue Hyperfluorescent OLEDs.

Achieving efficient and color-pure-blue emission in solution-processed organic light-emitting diodes (SOLEDs) remains a challenge due to poor triplet utilization and interfacial energy loss. We report high-efficiency blue hyperfluorescent (HF) SOLEDs that use a polymer/small-molecule hybrid emitting layer composed of a polymeric thermally activated delayed fluorescence (TADF) sensitizer, poly(10-(3-(4-(8-phenyloctyl)phenyl)-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-10H-spiro[acridine-9,9'-fluorene]), and a narrowband multiresonance TADF emitter. The polymer sensitizer enables efficient triplet harvesting and rapid reverse intersystem crossing, suppresses aggregation, and ensures effective energy transfer to the terminal emitter. In addition, self-organized polymeric hole injection layers are introduced to increase hole injection and suppress exciton loss at the interface. As a result, blue SOLEDs achieved a high external quantum efficiency of 32.7%, which is the highest reported to date for polymer-based TADF or HF OLEDs. This study demonstrates a polymer-sensitized blue HF OLED and offers a generalizable strategy for production of high-efficiency SOLED platforms.