Surface Engineering of Quantum Dots for Remarkably High Detectivity Photodetectors

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Colloidal quantum dots (CQDs) are promising for photodetector applications.
• Surface trap states in CQDs often limit device performance.
• Developing efficient passivation strategies is crucial for enhancing CQD photodetector capabilities.

Purpose of the Study:

• To develop ternary alloyed CdSeTe CQDs passivated with iodide-based ligands (TBAI) for UV-NIR photodetectors.
• To achieve few surface traps and high QD loading for improved device performance.
• To fabricate self-powered, broad-band photodetectors with enhanced sensitivity and stability.

Main Methods:

• Synthesis of ternary alloyed CdSeTe CQDs.
• In situ ligand exchange with tetrabutylammonium iodide (TBAI) for surface passivation and high QD loading.
• Fabrication of photodetector devices on semitransparent Ag nanowires/polyimide substrates.
• Characterization of device performance including photoresponsivity, response time, detectivity, and stability.

Main Results:

• CdSeTe CQDs passivated with TBAI exhibited significantly reduced surface trap states.
• The resulting photodetectors showed broad wavelength sensitivity from UV to NIR (300-850 nm).
• Devices achieved high photoresponsivity (53 mA/W), fast response time (<0.02s), and excellent detectivity (8 × 10^13 Jones at 450 nm).
• Exceptional stability was observed, retaining 98% responsivity after 2 months of air illumination without encapsulation.
• Self-powered operation was demonstrated without external bias voltage.

Conclusions:

• Ternary alloyed CdSeTe CQDs passivated with TBAI are effective building blocks for high-performance photodetectors.
• The developed photodetectors offer superior performance metrics compared to existing QD-based devices.
• These stable, self-powered, broad-band photodetectors are suitable for diverse environmental conditions and applications.