Aerosol-Jet Printed, High Performance MoS₂ Nanosheet Photodetectors Enabled by Megasonic Exfoliation

Printing solution-processed inks of 2D materials offers a scalable and cost-effective path towards mechanically flexible optoelectronics. In particular, aerosol jet printing (AJP) is a promising means to achieve all-printed circuits and systems, offering micrometer-scale resolution and broad ink processing capabilities. In this work, I will present aerosol-jet-printed, ultrahigh-responsivity photodetectors that consist of well-aligned, percolating networks of semiconducting MoS₂ nanosheets paired with printed graphene electrodes on flexible polyimide substrates. An MoS₂ ink containing high-aspect-ratio nanosheets with a large fraction of monolayers is obtained by electrochemical exfoliation, followed by megasonic atomization during AJP, which not only aerosolizes the inks but also further exfoliates the nanosheets during printing. The ink is also formulated with terpineol, a high-boiling-point solvent that is critical for achieving aligned nanosheets in uniform morphology. After printing, the devices undergo photonic annealing, which removes insulating residues from the film and yields quasi-ohmic contacts between MoS2 and graphene. The resultant photodetectors have responsivities exceeding 10³ A W⁻¹ in the visible range (515.6 nm), outperforming previously reported all-printed photodetectors by over three orders of magnitude. These photodetectors are also mechanically robust, withstanding over 1,000 bending cycles with negligible changes in device metrics. Overall, this work demonstrates that megasonic exfoliation coupled with modular design of AJP ink formulation not only preserves superlative optoelectronic properties of individual MoS₂ nanosheets, but also offers a scalable additive manufacturing scheme for mechanically flexible optoelectronics.