Generating Triplets in Organic Semiconductor Tetracene upon Photoexcitation of Transition Metal Dichalcogenide ReS₂

Abstract

We studied the dynamics of transfer of photoexcited electronic states in a bilayer of the two-dimensional transition metal dichalcogenide ReS 2 and tetracene, with the aim to produce triplets in the latter. This material combination was used as the band gap of ReS 2 (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 2 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.

Unraveling the Photophysics of Liquid-Phase Exfoliated Two-Dimensional ReS2 Nanoflakes

“…24−26 An in-depth study of the synthesis of crystalline few-layered ReS 2 flakes through liquid-phase exfoliation has been reported recently, and first reports indicate their promising potential for PV applications. 27,28 Although high-quality ReS 2 nanoflakes obtained through such exfoliation procedures are clearly promising materials, the nature and dynamics of elementary optical excitations in these novel materials are not yet known, limiting their potential use in applications such as light emission or photovoltaics.…”

“…Similar to other layered semiconductors, ReS 2 can be produced either through vacuum epitaxial growth, exfoliation from high-quality crystals, or direct colloidal synthesis. − Exfoliation, particularly through liquid-phase methods, is a cost-effective means to produce flakes of ReS 2 as it combines the advantages of solution processing (low cost and upscaling) while preserving high crystallinity, a persistent issue in direct colloidal synthesis methods. − An in-depth study of the synthesis of crystalline few-layered ReS 2 flakes through liquid-phase exfoliation has been reported recently, and first reports indicate their promising potential for PV applications. , Although high-quality ReS 2 nanoflakes obtained through such exfoliation procedures are clearly promising materials, the nature and dynamics of elementary optical excitations in these novel materials are not yet known, limiting their potential use in applications such as light emission or photovoltaics.…”

Two‐dimensional Transition metal Dichalcogenides as an Emerging Platform for Singlet Fission Solar Cells

“…In another study, Maiti et al demonstrated that 2D ReS 2 with a bandgap energy of 1.5 eV was able to sensitize the triplet state of tetracene (1.25 eV) within 5 ps, thus increasing the triplet quantum yield by up to 38% in tetracene (Figure 7b). [50]…”

“…Reproduced with permission. [50] 2021, American Chemical Society. (c) Band bending controlled by the thickness of MoS 2 changes the spatial extension of interlayer excitons at the heterojunction with ZnPc.…”

“…(b) The triplet transfer from ReS 2 to tetracene is indicated by the arrow. Reproduced with permission [50] . 2021, American Chemical Society.…”