A Hierarchical Self-Assembly-Induced Solid-State White-Light Emission from a Solution-Processed Single Polymer

Abstract

Researchers worldwide have invested significant effort in developing organic light-emitting diodes (OLEDs) for future display and lighting applications. However, achieving efficient and optimized white OLEDs by integrating diverse organic emitters across the visible spectrum is challenging. This study demonstrates the efficient operation of nondoped white OLEDs triggered by molecular tuning of copolymers (PTNAA 0.1 to PTNAA 50), thereby enriching the aggregation-induced emission (AIE) characteristics in a solution-processed single polymer. Remarkably, the synthesized copolymer, PTNAA 0.1, generates a bright and stable dual-band white light with a solid-state photoluminescence quantum yield (PLQY) of 87.7%, displaying a unique "nanoring-like" hierarchical self-assembly potentially driven by J-aggregate formation. Furthermore, PTNAA-based copolymers effectively diminish charge carrier trapping owing to their ambipolar charge transport characteristics, enabling efficient electroluminescence (EL). A solution-processed single-polymer-based OLED device fabricated with PTNAA 0.1 exhibited bright white light luminescence with an external quantum efficiency (EQE) of 6.75% with CIE coordinates of (0.33, 0.32), and maximum luminescence, current, and power efficiencies of 10553 cd m-2, 9.68 cd A-1, and 4.34 lm W-1, respectively. Moreover, theoretical (DFT and TD-DFT) studies confirm the competent energy transfer from fluorene to the PTNAA-gens. Our results corroborate materials design for solution-processed WOLEDs and concrete advances in solid-state lighting and display technologies.