Mixed-dimensional heterojunctions (MDHJs) combine materials of different dimensionality to take advantage of the desirable properties of the individual components. For example, composites of strongly absorbing zero-dimensional materials with two-dimensional (2D) nanosheets that possess high charge carrier mobility are promising candidates for light-responsive electronic components such as field effect transistors. Previous research has shown that physioadsorption of phthalocyanine (Pc) chromophores to 2D semiconducting materials increases the composite’s light sensitivity via electron transfer from the photoexcited state of Pc to the underlying 2D material. However, little is known about covalently bound Pc-2D material systems. The possibility for more robust composites with enhanced charge transfer warrants further investigation into covalent attachment of MDHJs. This research focuses on the impact of molecular bridge identity on charge transfer between covalently bound Zn-phthalocyanine (Zn-Pc) and molybdenum disulfide (MoS2) nanosheets. A series of Zn-Pc/MoS2 heterojunctions with covalent bridges of variable functionalization chemistry, length, conjugation, and rigidity were synthesized. Electronic coupling and charge transfer between the components were probed by photoluminescence, UV-Vis, and transient absorption spectroscopy. By characterizing the influence of bridge composition on charge transfer dynamics, this study will inform the design of future mixed-dimensional heterojunctions.

Impact of bridge chemistry on charge transfer between covalently bound zinc-phthalocyanine and MoS2 nanosheets

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ACS Fall 2022

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