High‐Contrast Handedness Inversion in Circularly Polarized Organic Ultralong Phosphorescence Enabled by an Antagonistic Chirality‐Offset Helical Superstructure

Abstract

ABSTRACT Dynamic and reversible control of circularly polarized ultralong room‐temperature phosphorescence (CP‐OURTP) is highly desirable for time‐gated chiroptical photonics. Yet, the simultaneous realization of handedness inversion and large dissymmetry factors remains challenging because inversion typically occurs near a net‐chirality cancellation point where the photonic bandgap (PBG) collapses. Here, we report a decoupled bilayer CP‐OURTP film that couples a room‐temperature phosphorescent polymer emitter with a photoresponsive chiral helical superstructure (CHS) engineered by an antagonistic chirality‐offset design. By pairing a high‐HTP chiral photoswitch with an oppositely handed static dopant, the net HTP reversibly crosses zero while remaining comparable in magnitude in the two photostationary states, thereby maintaining a robust PBG‐emission overlap on both sides of inversion. Consequently, the film delivers reversibly switchable g lum up to ±1.0 under alternating 365 and 530 nm irradiation, together with a phosphorescence quantum yield of 21.4%, an ultralong lifetime up to 388 ms, and stable operation over 50 switching cycles. The combined CP‐OURTP and selective circular‐polarization reflection enable high‐fidelity rewritable anti‐counterfeiting labels. This CHS‐engineering strategy provides a general route to CP‐OURTP materials with on‐demand chiroptical control for multi‐level information encryption and smart photonic devices.