Near-Infrared Room Temperature Phosphorescence from Single Polymers Containing Benzoselenadiazole Groups

Polymeric room temperature phosphorescence (RTP) materials have attracted increasing attention in advanced optoelectronic applications because they not only possess fantastic advantages of good flexibility and easy processing but can also be used as a rigid matrix to suppress nonradiative decay. However, limited by the energy gap law, it remains an enormous challenge to achieve near-infrared (NIR) RTP from a single polymer. Here, we demonstrate that a couple of polymers (UP2–1 and UP2–100) containing benzo-2,1,3-selenadiazole and ureidopyrimidinone (UPy) segments emit RTP in the NIR (731–768 nm) spectral range with a long lifetime of 1.19 ms. Theoretical calculations illustrate that the NIR RTP emissions stem from the lower-lying T1 level of the monomer with a donor–acceptor structure and electron-withdrawing benzo-2,1,3-selenadiazole acceptor, and the strong spin–orbital coupling between S1 and Tn facilitates the intersystem crossing process. Benefiting from the delayed emission characteristics, this emitter can exhibit decent electroluminescence performance. This work paves an avenue for the design of a simple single-polymer system with NIR RTP emission.