Sunlight‐Activated Hour‐Long Afterglow from Transparent and Flexible Polymers

Abstract Afterglow materials featuring long emission durations ranging from milliseconds to hours have garnered increasing interest owing to their potential applications in sensing, bioimaging, and anti‐counterfeiting. Unfortunately, polymeric materials rarely exhibit afterglow properties under ambient conditions because of the rapid nonradiative decay rate of triplet excitons. In this study, hour‐long afterglow (HLA) polymer films are fabricated using a facile molecular doping strategy. Flexible and transparent polymer films emitted a bright afterglow lasting over 11 h at room temperature in air, which is one of the best performances among the organic afterglow materials reported to date. Intriguingly, HLA polymer films can be activated by sunlight, and their cyan afterglow in air can be readily observed by the naked eye. Moreover, the HLA color of the polymer films could be tuned from cyan to red through the Förster resonance energy transfer mechanism. Their application in flexible displays and information storage has also been demonstrated. With remarkable advantages, including an hour‐long and bright afterglow, tunable afterglow colors, superior flexibility and transparency, and ease of fabrication, the HLA polymer paves the way for the practical application of afterglow materials in the engineering sector.