Revelation of room temperature liquid crystallinity and yellow-orange electroluminescence (EQE>7%) in a columnar self-assembled N-annulated perylene bisimide

Abstract

The synthesis of highly fluorescent compounds is a critical necessity to facilitate cost-effective and metal-independent production of organic light-emitting diodes (OLEDs). This investigation introduces a readily soluble, electron-deficient N-annulated perylene bisimide (PBI-NST) equipped with a swallow tail, exhibiting room temperature columnar oblique mesophase with a low clearing point and high photoluminescence quantum yield, positioning it as a promising candidate for efficient OLEDs. Leveraging the luminescent properties of PBI-NST, a series of OLED devices were fabricated with PBI-NST as the sole emitter and at various concentrations in CBP host material. Impressively, doped devices employing the compound at 0.5 wt% emitter within the host material CBP displayed an exceptional external quantum efficiency (EQE) of 7.2 %, accompanied by a luminance of 2689 cd/m2. Further, a voltage dependent emission tuning was also noticed. The notable increase in EQE is mainly attributed to the contributions of hybrid local and charge transfer (HLCT) and triplet–triplet annihilation (TTA) process. The substantial enhancement in EQE marks a significant advancement in the application of multifunctional columnar self-assembled materials for OLED development.