Efficient white-light emission from single polymer system with “spring-like” self-assemblies induced emission enhancement and intramolecular charge transfer characteristics
Over the past few decades, aggregation induced emission enhancement (AIEE) is marked as a powerful tool to offset the bottle-neck 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 the non-doped white light-emitting single layer polymer is scarce. We report here a novel orange-red emitting multifunctional organic fluorophore consisting of two terminal attachment of push–pull moieties separated by a biphenyl free rotor named BPPTA and its copolymers. High photoluminescence quantum yield (ΦPL) of 69.1 % is observed for BPPTA with strong intramolecular charge transfer (ICT) and AIEE characteristics. A meticulous investigation shows that the enhanced emission in the solid state is due to the formation of “J-aggregates” with ordered supramolecular self-assembly. Interestingly, BPPTA 0.1 exhibited unique ordered “spring-like” supramolecular self-assembly and significant diminish in charge trapping due to 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 15672 cd/m2, 9.30 cd/A and 7.98 lm/W, respectively. The DFT and TD-DFT analyses of BPPTA-gen and copolymer model systems have strongly typified the presence of an intramolecular charge transfer (ICT) characteristics. This is hitherto one of the best polymer system for dopant-host non-doped single layer two color polymer white organic light-emitting devices (PWOLEDs).