Generating Triplets in Organic Semiconductor Tetracene upon Photoexcitation of Transition Metal Dichalcogenide ReS.

We studied the dynamics of transfer of photoexcited electronic states in a bilayer of the two-dimensional transition metal dichalcogenide ReS and tetracene, with the aim to produce triplets in the latter. This material combination was used as the band gap of ReS (1.5 eV) is slightly larger than the triplet energy of tetracene (1.25 eV). Using time-resolved optical absorption spectroscopy, transfer of photoexcited states from ReS to triplet states in tetracene was found to occur within 5 ps with an efficiency near 38%. This result opens up new possibilities for heterostructure design of two-dimensional materials with suitable organics to produce long-lived triplets. Triplets are of interest as sensitizers in a wide variety of applications including optoelectronics, photovoltaics, photocatalysis, and photon upconversion.