Dual‐Path Exciton Harvesting Guided by Molecular Packing and Orientation Achieves Highly Efficient Deep‐Blue Emission

Abstract

ABSTRACT Efficient and color‐pure deep‐blue organic light‐emitting diodes (OLEDs) are of critical significance for next‐generation display technologies, yet the realization remains challenging owing to the stringent requirements of wide bandgap emitters, inefficient exciton utilization, and pronounced efficiency roll‐off. In this study, we proposed a dual‐path exciton harvesting strategy that combines high‐energy reverse intersystem crossing with triplet–triplet annihilation to improve exciton utilization. The new deep‐blue emitter PChCz, based on the chrysene moiety, exhibits favorable high‐energy reverse intersystem crossing from high‐lying triplet states, enabling non‐doped OLEDs with a peak external quantum efficiency of 21.3%. To alleviate triplet‐polaron annihilation at elevated current densities, a co‐deposited sensitizer is employed to reutilize low‐energy triplet via the triplet–triplet annihilation mechanism, thereby further improving the external quantum efficiency to 25.5% with suppressed roll‐off. Morphological analysis reveals that co‐deposition enhances compositional homogeneity and optimizes molecular orientation, which are conducive to efficient energy transfer and light outcoupling. Supported by rational molecular design and morphological control, the proposed dual‐path exciton harvesting mechanism presents an effective approach for the development of high‐performance deep‐blue OLEDs.