Efficient white-light emission from a single polymer system with “spring-like” self-assemblies induced emission enhancement and intramolecular charge transfer characteristics

Abstract

Over the past few decades, aggregation-induced emission enhancement (AIEE) has been marked as a powerful tool to offset the bottleneck problem of the aggregation-caused quenching (ACQ) effect in organic light-emitting diodes (OLEDs). However, the application of fluorophores with AIEE properties to enhance the efficiency of non-doped white-light-emitting single-layer polymers is scarce. However, we report herein a novel orange-red emitting multifunctional organic fluorophore consisting of two terminal attachments of push–pull moieties separated by a biphenyl free rotor named BPPTA and its copolymers. A high photoluminescence quantum yield (Φ_PL) of 69.1% was observed for BPPTA with strong intramolecular charge-transfer (ICT) and AIEE characteristics. A meticulous investigation showed that the enhanced emission in the solid state was due to the formation of “J-aggregates” with ordered supramolecular self-assembly. Interestingly, BPPTA 0.1 exhibited a unique ordered “spring-like” supramolecular self-assembly and a significant reduction in charge trapping due to its ambipolar charge-transport nature. As a result, pure and efficient white-light emission with Commission Internationale de l’Eclairage (CIE) coordinates of (0.32, 0.33) and maximum luminance, current and power efficiencies of 15 672 cd m⁻², 9.30 cd A⁻¹ and 7.98 lm W⁻¹, respectively, were displayed. The DFT and TD-DFT analyses of the BPPTA-gen and copolymer model systems strongly typified the presence of intramolecular charge transfer (ICT) characteristics. This was hitherto one of the best polymer system for dopant–host non-doped single-layer two-colour polymer white organic light-emitting devices (PWOLEDs).