A high-performance long-wave infrared photodetector based on a WSe 2 /PdSe 2 broken-gap heterodiode.

Layered narrow bandgap quasi-two-dimensional (2D) transition metal dichalcogenides (TMDs) demonstrated excellent performance in long-wave infrared (LWIR) detection. However, the low light on/off ratio and specific detectivity ( D *) due to the high dark current of the device fabricated using a single narrow bandgap material hindered its wide application. Herein, we report a type-III broken-gap band-alignment WSe ₂ /PdSe ₂ van der Waals (vdW) heterostructure. The heterodiode device has a prominently low dark current and exhibits a high photoresponsivity ( R ) of 55.3 A W ^-1 and a high light on/off ratio >10 ⁵ in the visible range. Notably, the WSe ₂ /PdSe ₂ heterodiode shows an excellent uncooled LWIR response, with an R of ∼0.3 A W ^-1 , a low noise equivalence power (NEP) of 4.5 × 10 ^-11 W Hz ^-1/2 , and a high D * of 1.8 × 10 ⁸ cm Hz ^1/2 W ^-1 . This work provides a new approach for designing high-performance room-temperature operational LWIR photodetectors.