• Xu, Jingsan
• Skidmore, Melissa
• Mcmurtrie, John
• Hirai, Tadahiko
• Brock, Aidan J.
• Xiao, Kevin
• Hui, Chenhui
• Meng, Peng

Abstract

Organic luminogens have been widely used in optoelectronic devices, bioimaging and sensing. Conventionally, the synthesis of organic luminogens require sophisticated, multi-step design, reaction and isolation procedures. Herein, the products of the melt-phase condensation of benzoguanamine (BG; 2,4-diamino-6-phenyl-1,3,5-triazine) at 370−410 ºC display interesting reaction-condition dependent luminescence properties, including photoluminescence (PL) at a variety of wavelengths in the visible spectrum and quantum efficiencies (PLQE) of up to 58% in powder form. With a simple and straightforward solvent washing procedure, the prominent blue luminescent component BG dimer was obtained in gram-scale with > 93% purity. The BG dimer exhibited distinct aggregation-induced emission (AIE) properties. PL measurements indicate that the electronically excited state of the BG dimer undergoes efficient intramolecular non-radiative deactivation in room-temperature solution, leading to a significantly reduced PLQE (< 1%) in solution. These non-radiative processes are substantially inhibited when the dimer existed in the form of crystals, solid aggregates in solution or being fixed in a rigid polymer film, resulting in a significant increase in the PLQE and lifetime. As a proof of concept, the BG dimer was incorporated as the emitting species in a solution-deposited emission layer in an organic light-emitting diode (OLED) and the electroluminescence properties of the resulting device are presented. This work not only provided new understanding for PL properties of self-condensation luminescent products, but also represented an unconventional strategy for large-scale preparation of organic luminogens with high purity.

Topics

• photoluminescence
• polymer
• melt
• washing