Tuning interfacial charge transfer in atomically precise nanographene-graphene heterostructures by engineering van der Waals interactions

Combining strong light absorption and outstanding electrical conductivity, hybrid nanographene-graphene (NG-Gr) van der Waals heterostructures (vdWHs) represent an emerging material platform for versatile optoelectronic devices. Interfacial charge transfer (CT), a fundamental process whose full control remains limited, plays a paramount role in determining the final device performance. Here, we demonstrate that the interlayer vdW interactions can be engineered by tuning the sizes of bottom-up synthesized NGs to control the interfacial electronic coupling strength and, thus, the CT process in NG-Gr vdWHs. By increasing the dimensions of NGs from 42 to 96 sp(2) carbon atoms in the polyaromatic core to enhance the interfacial coupling strength, we find that the CT efficiency and rate in NG-Gr vdWHs display a drastic increase of one order of magnitude, despite the fact that the interfacial energy driving the CT process is unfavorably reduced. Our results shed light on the CT mechanism and provide an effective knob to tune the electronic coupling at NG-Gr interfaces by controlling the size-dependent vdW interactions. (C) 2022 Author(s).

Automated summary

Hybrid nanographene-graphene (NG-Gr) van der Waals heterostructures offer a versatile material platform for optoelectronic devices. This study demonstrates that the interlayer vdW interactions can be engineered by tuning the sizes of bottom-up synthesized NGs, resulting in enhanced interfacial charge transfer efficiency and rate. The findings shed light on the charge transfer mechanism and provide a means to control the electronic coupling at NG-Gr interfaces.