Ultrafast hole transfer from monolayer ReS2 to thin-film F8ZnPc

We report a combined experimental and computational study on the charge transfer properties of heterostructures formed by monolayer 1T′-ReS2 and fluorinated zinc phthalocyanine, F8ZnPc. Two-dimensional (2D) ReS2 monolayer flakes were exfoliated from bulk crystals, and an F8ZnPc film with a thickness of 4 nm was thermally deposited on ReS2. Density functional theory shows that the two materials form a type-II band alignment. In transient absorption measurements, photocarriers are selectively excited in ReS2 and monitored in F8ZnPc. We found that holes in ReS2 can transfer to F8ZnPc on a timescale shorter than 0.35 ps. The transferred holes have a long lifetime in F8ZnPc on the order of 1 ns, confirming the lack of electron transfer. The efficient charge transfer from a 1T′ transition metal dichalcogenide monolayer to an organic semiconductor illustrates the feasibility of developing 2D/organic heterostructures with in-plane anisotropic electronic and optoelectronic properties.