Multi-band luminescence from a rare earth-based two-dimensional material

Photoluminescence (PL) emission in two-dimensional (2D) materials is of great interest for nanophotonics applications. While excitonic emission has been observed in numerous 2D materials, tunable multi-band luminescence is rare. Here, we present single-crystalline AgErP2Se6, a 2D material that exhibits bright, multi-band PL emission from Er3+ ions within the lattice. The emission bands cover a wide range (350- 1,550 nm), with ultra-narrow (as low as 0.5 nm at room temperature) emission peaks and room temperature lifetimes up to 4 ms. The intensities of the PL emission bands from the single crystals depend strongly on temperature and pressure, enabling sensing over a wide temperature and pressure range. Furthermore, the PL persists in exfoliated flakes down to at least 11 nm thick and demonstrates thickness-dependent Purcell enhancement. This work establishes 2D AgErP2Se6 as a multi-band luminescent emitter and sensor, poised to enable integration into a number of optoelectronic and nanophotonic applications.