Construction of sublimable pure organic ionic material with high solid luminescence efficiency based on anion-π+ interactions tuning strategy

Charged species with pi-conjugated moieties play a vital role in the development of organic electronic field, but the executable strategy of attaining high luminescent efficiency with sublimable pure organic salts is rare due to their inherent ionic nature and low vapor pressure, extremely restricting their application in the field of organic optoelectronics via common vacuum evaporation method. In this work, a series of central-type organic salts based polycyclic aromatic hydrocarbon (PAH) core are developed because of their potential higher luminescence efficiency than that of reported terminal-type organic salts like protonated pyridine framework, and they are equipped with aggregation-induced emission enhancement performance and tunable emission. The analyses of spectral data, crystal packing, and theoretical simulation demonstrate that rationally dispersing surface charge of large pi cation by regulating donor-acceptor (D-A) distribution facilitates to increase anion-pi+ interactions and suppress the free rotation of phenyl groups, contributing to the fluorescence enhancement in the solid state. Notably, after tuning counter-ions' steric hindrance and dispersed charges (BArF24-), the sublimable pure organic ionic materials are obtained with high solid luminescence efficiency, and its vacuum-evaporated organic light-emitting diode (OLED) is prepared based on pure organic salt with bright yellow emission. Such inspiring results offer us new alternative material system for the organic optoelectronics.

Automated summary

In this work, a series of central-type organic salts based on polycyclic aromatic hydrocarbon (PAH) core were developed, showing higher luminescence efficiency compared to reported terminal-type organic salts. By regulating the surface charge distribution, it was possible to increase anion-pi+ interactions and suppress free rotation of phenyl groups, leading to fluorescence enhancement in the solid state.