Large‐area, Ultra‐thin Organic Films with Both Photochromic and Phosphorescence Properties

Polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC) are the most commonly used polymers in plastic products. Therefore, endowing these polymers with unique optical properties would significantly enhance their overall technological value. Herein, we synthesized a phosphorescent molecule, 2,2'‐diphenyl‐3,3'‐bibenzofuran (DBF), with notable reversible photochromic properties (switching between colorless and deep red) as the guest and constructed a doped system with the above polymers as the hosts. All doped materials exhibited both room‐temperature phosphorescence and reversible photochromic properties. The guest molecule exhibited strong reversible cyclization activity and small conformational changes during the reaction process, as well as moderate rigidity of the host matrix, which enabled the uncommon coexistence of these two properties in the doped system. Finally, DBF/PET was successfully formed into a transparent and uniform film with a length of 200 m, a width of 20 cm, a thickness of only 60‐70 μm. This film exhibited excellent thermal‐stability, sensitivity, and resistance to photo‐fatigue, indicating its applicability in industrial production.