In hot exciton materials, the excitons from the high-lying triplet state (Tn, n≥2) can be efficiently converted into the singlet (Sm, m≥1) state via reverse intersystem crossing (RISC) process due to the staggered energy level arrangement, which maximizes the use of the triplet exciton and theoretically achieves a maximum internal quantum efficiency (IQE) of 100%. Hot exciton materials not only break the exciton utilization limitation of traditional fluorescent materials and triplet-triplet annihilation materials, but also overcome the serious efficiency roll-off of thermally activated delayed fluorescent (TADF) materials at high current density, exhibiting unique advantages in the electroluminescence. Blue light has long been the short board of the organic photoelectric full-color display. Compared with the phosphorescent and TADF materials with unsatisfying color purity and inferior stability, hot exciton materials can achieve higher-quality emission in blue devices, exhibiting excellent performance even in the deep-blue region. In this review, the representative blue-emitting hot exciton materials reported recently are summarized, the light-emitting mechanism and design strategy are elaborated, and a full vision of its development is made.
