Panchromatic luminescent D–π–A benzothiazoles with different π-bridging modulation: design, synthesis and application in WLED devices

Abstract

White light-emitting diodes (WLEDs) are gradually replacing traditional lighting devices and are becoming a mainstream photosource, as they have advantages of low energy consumption and high efficiency. However, a higher brightness and color purity are still required for the development of WLEDs. In this work, we have constructed donor (D)–π–acceptor (A)-type fluorescent small molecules using simple benzothiazole and dimethylamine as electron donor/acceptor groups, respectively. Six compounds with full-color luminescence have been obtained by introducing benzene, thiophene, and CC double-bond units to modulate the π-bridge length. These six compounds covered the entire visible spectrum, not only in solution, but also in the aggregation state. Moreover, most of the compounds had a high luminescence efficiency. The fluorescence quantum yields of PLB2 and PLB3 are even close to 1.0. We have used PLB1, PLB3, PLB4, and PLB6, which display good luminescence properties in both the aggregated and dispersed states, to fabricate LEDs. Two PLB4-based WLEDs have also been prepared, designated as warm-white and cool-white devices. Their luminous efficiencies were measured as 115.81 lm W⁻¹ and 95.31 lm W⁻¹ and their color rendering indices (CRI) were evaluated as 60 and 80, respectively. These key parameters exceeded those of commercial WLEDs. In addition, four compounds have been utilized to prepare blue, green, yellow, and near-infrared LEDs, all of which surpassed the performances of existing commercial LEDs.