Compositionally Tunable 2D PtSe <i> _x </i> Te <i> _y </i> Alloys Synthesized via Thermally Assisted Conversion for Mid‐Wave Infrared Photodetection

Abstract Mid‐wave infrared (MWIR) photodetectors play a crucial role in thermal imaging, environmental monitoring, and medical diagnostics due to their ability to detect subtle thermal signatures. However, advancements in this field have been limited by the scarcity of suitable semiconductor materials and the high cost of epitaxial growth techniques. 2D materials have emerged as a promising new class of candidates for MWIR photodetectors, offering tunable optical properties and compatibility with scalable, cost‐effective fabrication methods. While band gap tuning in the MWIR range has thus far been achieved through thickness modulation and defect engineering, compositional engineering remains largely unexplored. Here, broadband band gap tuning across the MWIR spectrum is demonstrated via compositional engineering in a 2D PtSe x Te y system synthesized through direct thermally assisted conversion. Optical characterization reveals a strong correlation between composition and band gap. As the Te content increases and the band gap narrows, a photodetector based on a p‐type PtSe x Te y /n‐type Si heterojunction exhibits significantly enhanced response to 800 °C blackbody radiation, indicating improved MWIR detection capability. These findings underscore the potential of compositional engineering as a straightforward and effective strategy for developing next‐generation MWIR photodetectors for advanced optoelectronic applications.