文摘
Hydrocarbon oligomers X9F, including S9F, D9F, and T9F as monomer, dimer, and trimer, respectively, were designed and prepared on the basis of indirect linkage and 9,9-diphenylfluorene (S9F) as repeat unit to form planar, linear, and V-shaped configurations without polarity variation and function amplification. The identical optical and electrochemical properties of X9F were achieved because of the effectively blocked intramolecualr electronic interactions by indirect linkage, including the same T1 value of 2.98 eV, high enough for hosts in blue phosphorescent organic light-emitting diodes (PHOLEDs), and the approximate FMO energy levels, which established the basis for selective investigation of independent configuration effect on the optoelectronic performance of host materials. Density function theory simulation manifested the frontier molecular orbital (FMO) location extension after oligomerization and the specific T1 locations on peripheral fluorenyls in X9F, giving rise to their different carrier-transporting abilities and host-localized triplet鈥搕riplet annihilation (TTA) and triplet鈥損olaron quenching (TPQ) effects. As a result, D9F with the linear and locally unsymmetrical configuration revealed electron-predominant characteristics for charge balance, restrained triplet interaction for TTA suppression, and partially separated FMO and T1 locations for TPQ suppression. Consequently, the low driving voltages and the favorable maximum efficiencies, such as 鈭?1% for external quantum efficiency (EQE), as well as reduced roll-offs less than 8% for EQE at 1000 cd鈥塵鈥?, were achieved by D9F-based blue PHOLEDs as the highest performance among X9F, in which device efficiencies were improved by 50% compared to that of conventional polarized host mCP. It is conceivable that molecular configuration has significant effects on electrical properties and quenching effects of organic semiconductors with remarkable influence on intermolecular interplay and excited-state locations.