Highly efficient blue crystalline organic light‐emitting diodes enabled by a hot exciton sensitizer PyPO

Sensitizing fluorescent materials enables fast and efficient exciton utilization, providing an effective approach to improving the performance of organic light‐emitting diodes (OLEDs) beyond new material design. However, conventional OLEDs usually adopt amorphous structures, which limit efficient photon output under low driving voltages. In this work, two fabrication methods for sensitization‐based fluorescent OLEDs using crystalline host matrix (CHM) are proposed. By leveraging the high carrier mobility of CHM and the efficient exciton collection of the hot exciton material PyPO, two sensitized crystalline organic light‐emitting diodes (via hot exciton sensitizer type and exciton nanoaggregates type) exhibit excellent electroluminescence, with maximum external quantum efficiencies of 9.12% and 7.03%, respectively. Both OLEDs exhibit fast turn‐on behavior, with rapid increases in luminance and current density under the same driving voltage. This leads to improved photon output and reduced Joule heat loss ratio from series resistance. Integrating sensitization strategies into crystalline materials provides a novel pathway toward low‐power, high‐brightness OLEDs.