New Breakthrough In Quantum Dot Sensors

A Cardiff-led team has developed a high-performance near-infrared quantum dot sensor with record responsivity, paving the way for low-light biomedical imaging and next-gen optical communications.

An international research team led by Dr Bo Hou has developed a new type of high-responsivity image sensor that opens new avenues in low-dose near-infrared imaging and communication technologies.

The Cardiff team has created a solution-processed colloidal quantum dot phototransistor using lead sulfide (PbS) quantum dots modified with long-chain ligands. The resulting devices deliver exceptional responsivity of up to 20,000 A/W and demonstrate stable image communication under low-light conditions.

The study, published in Light: Science & Applications - a leading journal in Nature - is titled “High Responsivity Colloidal Quantum Dots Phototransistors for Low-Dose Near-Infrared Photodetection and Image Communication.”

“Locking” quantum dots to unlock performance
Near-infrared detectors are essential for applications in biomedical sensing, mobile health, automotive vision, and optical communication. However, traditional detectors based on materials like InGaAs and HgCdTe are expensive and energy-intensive to produce.

Colloidal PbS quantum dots are a promising low-cost alternative, but their performance has long been limited by charge leakage and trap-induced losses. To overcome this, the Cardiff team employed long-chain dithiol molecules, such as 1,10-decanedithiol (DDT), which act as molecular “locks” that restrict lateral electron movement between quantum dots while enhancing vertical charge injection into the device’s semiconductor channel.

Imaging in the dark
Systematic experiments confirmed the unique advantages of the approach:

• Lateral leakage currents were suppressed by four orders of magnitude compared to traditional short-chain ligands.
• Grazing-incidence X-ray diffraction (GIXRD) showed disrupted quantum dot alignment, minimizing unwanted conduction paths.
• Photoluminescence quenching and defect analysis demonstrated enhanced carrier injection and reduced recombination losses.

These improvements translated into a device with industry-leading detectivity of 10¹⁴ Jones, capable of transmitting grayscale images using low-light near-infrared signals—marking a significant advance toward real-time optical communication in dark environments.

It’s like a high-precision camera designed for ultra-low light, with clear potential for imaging through biological tissue or secure optical communication. Dr Bo Hou

Towards real-world impact
The technology holds promise for a range of applications, including:

• Low-dose medical imaging
• Night-vision automotive systems
• Optical communication in the Internet of Things (IoT)
• Security surveillance
• Wearable health devices

This discovery was made possible by funding from the UK’s Engineering and Physical Sciences Research Council (EPSRC), the Royal Society, the Welsh Government's Sêr Cymru programme —Enhancing Competitiveness Equipment Awards and the Leverhulme Trust.