Non-Toxic CuInS₂ /ZnS Colloidal Quantum Dots for Near-Infrared Light-Emitting Diodes

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Ternary copper indium sulfide (CuInS2) quantum dots (QDs) offer tunable photoluminescence from visible to near-infrared (NIR) wavelengths.
• CuInS2 QDs are attractive for consumer electronics due to their lack of toxic heavy metals like lead (Pb), cadmium (Cd), or arsenic (As).
• Existing research on NIR-emitting CuInS2 QDs shows limited efficiency, especially beyond 900 nm.

Purpose of the Study:

• To develop an efficient synthesis method for NIR-emitting CuInS2/ZnS quantum dots.
• To achieve high photoluminescence quantum efficiency (PLQE) and external quantum efficiency (EQE) in the NIR region.
• To demonstrate the potential of these eco-friendly QDs for advanced optoelectronic devices.

Main Methods:

• Facile synthesis of CuInS2/ZnS quantum dots using a dual sulfur precursor approach (1-dodecanethiol and hexamethyldisilathiane).
• Utilizing reactive hexamethyldisilathiane to promote faster nucleation and enhance emissive copper-deficiency sites.
• Fabrication of NIR light-emitting diodes (LEDs) using the synthesized CuInS2/ZnS QDs.

Main Results:

• Achieved high PLQE of 65% at a 920 nm emission wavelength.
• Demonstrated NIR LEDs with an EQE of 8.2%, comparable to state-of-the-art PbS and InAs QD LEDs.
• The emission wavelength surpasses that of lead iodide perovskites.

Conclusions:

• This work presents one of the first reports of efficient NIR LEDs based on environmentally benign CuInS2 QDs.
• The developed synthesis method overcomes previous limitations in NIR emission efficiency for CuInS2 QDs.
• These findings open promising avenues for novel applications in consumer electronics and optoelectronics.