Stable Deep-Blue Electroluminescence from Hierarchical Crystalline Structure Based on Planar Conformational Terfluorenes: Benefits of Preventing Defect Structures Formation

Liner-type organic conjugated molecules with 1D & pi;-electron delocalization present conformation-dependent intramolecular optoelectronic behavior. Significantly different from non-planar ones, the coplanar conformational backbone of & pi;-conjugated molecules can enhance intramolecular & pi;-electron delocalization and dominate intermolecular & pi;-electron coupling, which are the fundamental parameters for improving their optoelectronic properties. Herein, the effect of the formation of coplanar conformation on intermolecular packing and optoelectrical properties of liner-type steric terfluorene (DSFX-SFSO) toward solution-processed deep-blue organic light-emitting diodes (OLEDs) is systematically demonstrated. Firstly, uniform and continuous crystalline films based on the planar conformational DSFX-SFSO molecules are achieved via thermal annealing at 160 & DEG;C, which can avoid microscale crystallization processing. Contrary to amorphous ones, these hierarchical crystalline films present robust deep-blue emission with an efficiency of > 60%, due to the suppression of defect structures. More interestingly, this hierarchical crystalline film has a stable and efficient deep-blue electroluminescence (CIE: 0.15, 0.09) without the obvious defective green-band emission, even at 500 mA cm(-2), also further confirming the excellent and perfect molecular landscape to obtain single-chromophore excitonic behavior from single planar-terfluorene segments. Therefore, obtaining a uniform hierarchical structure based on planar conformational molecules is an effective strategy to optimize the optoelectrical properties for optoelectronic applications.