Defect-engineering of liquid-phase exfoliated 2D semiconductors: stepwise covalent growth of electronic lateral hetero-networks.

Two-dimensional (2D) in-plane heterostructures display exceptional optical and electrical properties well beyond those of their pristine components. However, they are usually produced by tedious and energy-intensive bottom-up growth approaches, not compatible with scalable solution-processing technologies. Here, we report a new stepwise microfluidic approach, based on defect engineering of liquid-phase exfoliated transition metal dichalcogenides (TMDs), to synthesize 2D hetero-networks. The healing of sulfur vacancies in MoS and WS is exploited to controllably bridge adjacent nanosheets of different chemical nature with dithiolated conjugated molecular linkers, yielding solution-processed nm-scale thick networks with enhanced percolation pathways for charge transport. In-plane growth and molecular-driven assembly synergistically lead to molecularly engineered heterojunctions suppressing the formation of tightly bound interlayer excitons that are typical of conventional TMD blends, promoting faster charge separation. Our strategy offers an unprecedented route to chemically assemble solution-processed heterostructures with functional complexity that can be further enhanced by exploiting stimuli-responsive molecular linkers.