Organic π-conjugated trimers as fluorescent molecules for colorful electroluminescence

Abstract

Organic fluorescent emitters based on π-conjugated small molecules show tremendous potential for display, lighting, and bio-imaging applications. However, these emitters face challenges of aggregation-caused quenching and limitations of color range caused by synthetic complexity and undesirable efficiency and quantum yield. In this work, by using quinoxaline/2,1,3-benzothiadiazole as central electron acceptors, and employing carbazole/thiophene/3,4-ethylenedioxythiophene as terminal electron donors, a series of π-conjugated fluorescent trimers with very low molecular weights (M_w = 294–466) were designed and synthesized. Modulating the molecular structure through the incorporation of distinct electron donor and acceptor moieties, broad spectral tuning from blue to red in the π-conjugated trimers was achieved. These conjugated trimers when applied as emitting layers in electroluminescent devices, particularly organic light-emitting diodes (OLEDs), exhibit high brightness and color-tunable electroluminescence (EL) peaks from 528 to 605 nm. The meticulously optimized device demonstrates excellent performance with a high brightness of 3857.19 cd m⁻², and an external quantum efficiency (EQE) of 2.29%. These π-conjugated trimers, synthesized by a simple synthesis process, present a viable avenue for low-cost luminescence lighting and display applications.