Synthesis of Core–Shell Te@Se Quantum Dots and Their Broadband Photodetector Performance in Low Concentration Electrolytes

Along with the increased attention of core–shell heterojunction quantum dots (QDs), there have been recent strong efforts to improve their practical applications by developing the synthetic approaches. In this work, uniform Te@Se core–shell QDs have been successfully fabricated via combining liquid-phase exfoliation and epitaxial growth methods, where the similar lattice structures of the materials from the same main group can effectively solve the lattice mismatch issue. Theoretical calculations reveal that the Te@Se material is a Type-I heterojunction with favorable initial electron transfer from core Te to shell Se upon formation. The photo-response performance of Te@Se QDs is systematically investigated by producing photoelectrochemical type photodetectors in low concentration electrolytes (0.1–10 mM), for which optimized photocurrent density (32.63 µA/cm 2 ) and photoresponsivity (1564 µA/W) could be achieved. The device also exhibits fast response and excellent stability, which could overcome instability issues in high-concentration electrolytes and expand the practical applications.