Black Phosphorus (bP) is a highly promising host material for future optoelectronic devices operating in the mid-wavelength infra-red (MWIR) regime of 3-5 um. bP is the most stable allotrope of phosphorous with a bulk direct bandgap of 0.3 eV that is highly tunable by alloying, applying strain, and varying the thickness, and with many remarkable electronic and optical properties ranging from low surface recombination velocity to high carrier mobility. Both MWIR LEDs and photodetectors based on mechanically exfoliated bP flakes operating at room temperature have shown superior performance to counterparts based on II-VI and III-V semiconductors with comparable bandgaps. However, scaling up these devices has been challenged by the limited lateral dimension of exfoliated bP flakes and the inherent difficulty of synthesizing wafer-scale monocrystalline bP film.
We report the formulation of a 2D ink consisting of bP particles dispersed in an organic solvent and the synthesis of a pinhole-free, centimeter-scale bP film based on this ink. We find that this bP film largely retains the optical properties of exfoliated flakes and exhibits strong PL emission in the MWIR. Furthermore, we report the potential to synthesize inks that emit at different wavelengths by changing bP particle size and the consequent effective bandgap. This paves the way for further developments in a plethora of sensing, spetroscopy, and imaging technologies based on multi-colored, highly-efficient MWIR light sources.
Project is currently funded by: Federal