The fluorescence dyes were dominant species of the near-infrared (NIR) dyes, but the energy gap of the NIR dyes between S1 state and S0 state is generally small to induce the ultrafast internal conversion dynamics to quench the NIR emission of the fluorescence dyes. Therefore, the quantum yield of the fluorescence NIR dyes is usually low. On the other hand, the organic dyes with room-temperature phosphorescence (RTP) in the NIR region could prevent the ultrafast internal conversion dynamics quenching because of the T1 state and S0 state the organic molecules are spin forbidden.
Recently, scientists in China reported a new assumption to construct efficient NIR materials based on the energy gap law on the National Science Review. In addition, a series of metal-free RTP films with NIR emission was constructed based on the assumption, and the first phosphorescence-based half-subtractor operation was also developed based on the stimuli-responsive properties of the dyes.
