Surface Engineering of Quantum Dots for Remarkably High Detectivity Photodetectors

Ternary alloyed CdSe x Te 1– x colloidal QDs trap-passivated by iodide-based ligands (TBAI) are developed as building blocks for UV–NIR photodetectors. Both the few surface traps and high loading of QDs are obtained by in situ ligand exchange with TBAI. The device is sensitive to a broad wavelength range covering the UV–NIR region (300–850 nm), showing an excellent photoresponsivity of 53 mA/W, a fast response time of ≪0.02s, and remarkably high detectivity values of 8 × 10 13 Jones at 450 nm and 1 × 10 13 Jones at 800 nm without an external bias voltage. Such performance is superior to what has been reported earlier for QD-based photodetectors. The photodetector exhibits excellent stability, keeping 98% of photoelectric responsivity after 2 months of illumination in air even without encapsulation. In addition, the semitransparent device is successfully fabricated using a Ag nanowires/polyimide transparent substrate. Such self-powered photodetectors with fast response speed and a stable, broad-band response are expected to function under a broad range of environmental conditions.