Dual-Mode White Light Emissions from a Single Copolymer with an Ultralong Phosphorescence Lifetime

Polymeric white-light-emitting materials have received extensive attention due to their excellent flexibility, easy processing, and good thermal stability. However, to develop a kind of polymer with dual-mode white light emissions, especially those accompanying ultralong afterglows, remains greatly challenging. In this work, two copolymers with different feeding ratios of carbazole-dibenzofuran, 4-bromo-1,8-naphthalimide, and N-isopropylacrylamide are designed and synthesized through photo-polymerization upon ultraviolet (UV) irradiation. The obtained polymer P1 films exhibit an ultralong phosphorescence lifetime of 1.86 s with decent quantum efficiency. Notably, cold white light emissions are obtained under UV irradiation with different excitation wavelengths. After removing the irradiation source, excitation-dependent and time-dependent afterglows are engendered, including warm white afterglows with Commission Internationale de l’éclairage (CIE) coordinates of (0.31, 0.37). Interestingly, after introducing fluorine (F) atoms into the polymer films, standard white afterglows with CIE coordinates of (0.34, 0.33) are achieved, which originate from the blue delayed fluorescence and yellow phosphorescence. The dual-mode multicolor emission properties of the polymers hold great promise for advanced anti-counterfeiting applications.