Highly Efficient Amorphous Polymer-Based Ultralong Phosphorescence Enabled by Intense Repulsive Interactions

Abstract

Amorphous polymer-based materials combining high optical transparency, mechanical flexibility, and the potential for low-cost scalability and processing, are attractive in the vibrant field of ultralong organic phosphorescence (UOP). However, developing amorphous polymer-based UOP materials with high quantum efficiency (Ф_P) remains a formidable challenge because the inherently loose polymer networks lead to the violent non-radiative transition and quenching processes of triplet excitons. Herein, a series of amorphous polymer-based UOP materials are fabricated by doping organic phosphors (SA, DA, and TA) composed of triphenylamine units modified with different numbers of carboxyl groups into polyvinyl alcohol (PVA) matrix. These experimental and computational results indicate that the resulting polymer films (SA/PVA, DA/PVA, and TA/PVA) exhibit the gradually enhanced UOP, which is attributed to the increased intermolecular hydrogen-bonded interactions, enabling incremental repulsive interactions between the isolated chromophores and PVA matrix, resulting in the reduced dissipation of triplet excitons through a non-radiative transition. Remarkably, TA/PVA has an optimal Ф_P of up to 77.5%, which is a record Ф_P among the reported heavy-atom-free amorphous polymer-based UOP materials. Given the bright afterglow emission and solution-processable properties, the promise of transparent, flexible, and large-area paints for display and illumination are demonstrated. This study will provide a design strategy to enhance the quantum efficiency of amorphous phosphorescent materials, showing great promise in flexible electronics.