Black phosphorus ink formulation for inkjet printing of optoelectronics and photonics

Black phosphorus is a two-dimensional material of great interest, in part because of its high carrier mobility and thickness dependent direct bandgap. However, its instability under ambient conditions limits material deposition options for device fabrication. Here we show a black phosphorus ink that can be reliably inkjet printed, enabling scalable development of optoelectronic and photonic devices. Our binder-free ink suppresses coffee ring formation through induced recirculating Marangoni flow, and supports excellent consistency (<2% variation) and spatial uniformity (<3.4% variation), without substrate pre-treatment. Due to rapid ink drying (<10 s at <60 degrees C), printing causes minimal oxidation. Following encapsulation, the printed black phosphorus is stable against long-term (>30 days) oxidation. We demonstrate printed black phosphorus as a passive switch for ultrafast lasers, stable against intense irradiation, and as a visible to near-infrared photodetector with high responsivities. Our work highlights the promise of this material as a functional ink platform for printed devices.