Multifunctional van der Waals PdSe2 for light detection, guiding and modulation.

Modern optoelectronic devices demand materials that can perform multiple, often conflicting functions, such as acting as metals for interconnects, dielectrics for waveguides, and semiconductors for light emission and detection. The integration of these materials is challenging, slowing industry progress and increasing costs. It inspired an intensive search for an optoelectronic response within a single material. Here, we reveal that palladium diselenide (PdSe2) provides an answer to this quest owing to its band structure. It exhibits a semimetallic band structure with a large bandgap for interband transitions responsible for semiconductor-metallic nature. This duality enables PdSe2 to function as both a photodetector and a waveguide, integrating two traditionally incompatible responses. As a result, our findings provide a full picture of PdSe2 optoelectronic properties, paving the way for its use in multifunctional optoelectronic applications.