Enhancing Photon Upconversion with Thermally Activated Sensitization and Singlet Energy Collection

Photon upconversion microcrystals based on triplet-triplet annihilation (TTA) were developed involving thermally activated energy transfer and singlet energy collection mechanism. Efficient solid-state upconversion with apparent anti-Stokes shift of 0.8 eV was achieved and the upconversion quantum yield was increased by 40% by the singlet energy collector which inhibited the back energy transfer from the upconverted annihilator to the sensitizer. The improvement in the upconversion microcrystals practically benefited upconversion-driven photoproduction of hydrogen, demonstrating potentials of solid-state TTA upconversion materials in optoelectronics and photocatalysis.