Circularly Polarized Room-Temperature Phosphorescence with an Ultrahigh Dissymmetry Factor from Carbonized Polymer Dots by Stacked Chiral Photonic Films

Developing circularly polarized room-temperature phosphorescent (CPRTP) materials with a high dissymmetry factor (g_lum) and long afterglow is very attractive but highly challenging. Here, a CPRTP emission featuring ultrahigh g_lum value and desired visualization characteristic in a bilayer composite photonic film is achieved for the first time. In the constructed system, N and P co-doped carbonized polymer dots (NP-CPDs) are dispersed into polyvinyl alcohol (PVA) as the phosphorescent emitting layer, and helically structured cholesteric polymer films are used as selective reflective layers to convert the unpolarized emission of NP-CPDs into circularly polarized emission. On the basis of the modulation of the helical structure period of the cholesteric polymer, the bilayer composite film enables NP-CPDs to obtain a high g_lum value. Notably, the optimized photonic film emits CPRTP with g_lum as high as 1.09 and a green afterglow lasting above 8.0 s. Moreover, the composite photonic array films featuring information encryption characteristics are developed by modulating the liquid crystal phase of the cholesteric polymer film and the dot coating position of the NP-CPDs/PVA layer, thus expanding the application of CPRTP materials in cryptography and anti-counterfeiting.