Anisotropy-guided molecular engineering for stable blue phosphorescent organic light-emitting diodes
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Blue phosphorescent organic light-emitting diodes (PhOLEDs) have been developed as one of the promising display technologies. However, large energy band gaps and high driving voltages induce exciton and charge leakage within emissive layers, causing rapid device degradation. Despite the emergence of electron-blocking materials (EBMs), a limited understanding of their molecular structures poses a challenge in achieving triplet confinement while maintaining charge balance. Here, we present a design strategy for EBMs concurrently controlling T1 and molecular arrangements. Four EBMs with high T1 are developed based on asymmetric orthogonal geometries. X-ray crystallographic analyses reveal that the EBM with the most asymmetric charge distributions exhibits a herringbone crystal packing and a face-on orientation, which promotes hole transport. The power efficiency and operational lifetime of the corresponding blue PhOLEDs increase by 24% and 21%, respectively, compared to a traditional EBM.