title: Ultrafast Charge Transfer and Hybrid Exciton Formation in 2D/0D Heterostructures.
abstract: Photoinduced interfacial charge transfer is at the heart of many applications, including photovoltaics, photocatalysis, and photodetection. With the emergence of a new class of semiconductors, i.e., monolayer two-dimensional transition metal dichalcogenides (2D-TMDs), charge transfer at the 2D/2D heterojunctions has attracted several efforts due to the remarkable optical and electrical properties of 2D-TMDs. Unfortunately, in 2D/2D heterojunctions, for a given combination of two materials, the relative energy band alignment and the charge-transfer efficiency are locked. Due to their large variety and broad size tunability, semiconductor quantum dots (0D-QDs) interfaced with 2D-TMDs may become an attractive heterostructure for optoelectronic applications. Here, we incorporate femtosecond pump-probe spectroscopy to reveal the sub-45 fs charge transfer at a 2D/0D heterostructure composed of tungsten disulfide monolayers (2D-WS2) and a single layer of cadmium selenide/zinc sulfide core/shell 0D-QDs. Furthermore, ultrafast dynamics and steady-state measurements suggested that, following electron transfer from the 2D to the 0D, hybrid excitons, wherein the electron resides in the 0D and the hole resides in the 2D-TMD monolayer, are formed with a binding energy on the order of ∼140 meV, which is several times lower than that of tightly bound excitons in 2D-TMDs.
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Abdelaziz
authors.initials: A
authors.lastname: Boulesbaa
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: Wang
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Masoud
authors.initials: M
authors.lastname: Mahjouri-Samani
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Mengkun
authors.initials: M
authors.lastname: Tian
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Puretzky
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Ilia
authors.initials: I
authors.lastname: Ivanov
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Rouleau
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: Xiao
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Bobby G
authors.initials: BG
authors.lastname: Sumpter
authors.affiliation: Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: David B
authors.initials: DB
authors.lastname: Geohegan