Red Room‐Temperature Afterglow Emissions of Polymer‐Based Doped Materials by Phosphorescence Förster‐Resonance Energy Transfer

Abstract A newly emerged and attractive strategy to obtain afterglow is the use of the Förster‐resonance energy transfer (FRET) from an energy donor with room‐temperature phosphorescence (RTP) to an energy acceptor with fluorescence. Due to the transfer of energy between molecules with different emissions, it is possible to develop the ultralong and long‐wavelength afterglow materials. However, there are few reports on red afterglow materials with emission wavelengths up to 650 nm because of the difficulty of accurate design of chemical structures. Herein, a series of red afterglow materials with emission wavelengths of 650 nm are constructed using polyvinylpyrrolidone as the host, multisubstituted isoquinolines as the guests, and triphenylamine‐based dicyanomethylene‐4H‐pyran derivative as the energy acceptor. Two‐component host‐guest materials exhibit yellow‐green, yellow, and orange RTP with delayed lifetimes of 205‐301 ms and phosphorescence quantum yields of 5.3‐13.2%, which originate from the guests in a rigid microenvironment provided by the host polymer. Three‐component doped materials exhibit red afterglow with a delayed lifetime of 11‐83 ms and an emission quantum yield of 16.2‐22.1%, which is determined to be delayed fluorescence caused by triplet‐to‐singlet FRET from isoquinolines to dicyanomethylene‐4H‐pyran derivative. This work provides inspiration for the development of doped materials with long‐wavelength room‐temperature afterglow.