High-Contrast Handedness Inversion in Circularly Polarized Organic Ultralong Phosphorescence Enabled by an...

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.