Simultaneously High Upconversion Efficiency and Large Anti‐Stokes Shift by Using Os(II) Complex Dyad as Triplet Photosensitizer

Abstract To extend the triplet lifetime of photosensitizer, two new osmium complex dyads, with Os(phen)₃ as triplet energy donor and 9,10‐diphenylanthracene (DPA) as energy acceptor, namely Os(phen)₃‐DPA and Os(phen)₃‐BDPA, are synthesized and characterized. The triplet lifetime of Os(phen)₃‐DPA dyad is significantly extended to 1.1 μs by introducing triplet energy acceptor DPA to activate the intramolecular triplet energy transfer from the Os(phen)₃ to DPA units. By developing the triplet–triplet annihilation upconversion piars of Os(phen)₃‐DPA and 9‐phenyl‐10‐(p‐tolyl)anthracene, the deep‐red light (at 663 nm) is upconverted to the blue‐violet emission (at 415 nm) in 1,2‐dichloroethane solution, and the highest upconversion quantum yield of 9.7% is achieved with a large anti‐Stokes shift of 1.12 eV.