U.S. Researchers Utilize Eco-Friendly Colloidal Quantum Dots to Detect Infrared Light, Achieving Visual Sensing in Dark Environments

Infrared camera manufacturers are facing an increasingly severe issue: the toxic heavy metals in infrared detectors are increasingly being banned by environmental regulations, forcing companies to choose between performance and compliance. This regulatory pressure is slowing down the widespread application of infrared detectors in civilian fields, while at the same time, the demand in areas such as autonomous vehicles, medical imaging, and national security continues to grow.

According to foreign media reports, researchers at the NYU Tandon School of Engineering have unveiled a potential solution that uses environmentally friendly quantum dots to detect infrared light without relying on mercury, lead, or other restricted materials. The related research paper was published in the journal ACS Applied Materials & Interfaces.

Image Source: New York University Tandon School of Engineering

Researchers have used colloidal quantum dots to revolutionize the outdated, expensive, and cumbersome processing of infrared detectors. The manufacturing process of traditional devices is slow and precise, almost requiring the placement of atoms one by one onto the pixels of the detector—like assembling a puzzle piece by piece under a microscope.

Colloidal quantum dots are synthesized entirely in solution, resembling a modulated ink, and can be deposited using scalable coating techniques similar to those used in roll-to-roll manufacturing for packaging or newspapers. This shift from cumbersome assembly to solution-based processing significantly reduces manufacturing costs and opens the door to a wide range of commercial applications.

"The industry is facing a 'perfect storm': environmental regulations are becoming increasingly stringent, while the demand for infrared imaging is experiencing explosive growth," said Ayaskanta Sahu, a senior author of the study and an associate professor in the Department of Chemical and Biomolecular Engineering (CBE) at New York University Tandon School of Engineering. "This presents a real bottleneck for companies trying to scale up the production of thermal imaging systems."

Another challenge faced by researchers is to ensure that quantum dot inks have sufficient conductivity to transmit incoming light signals. They achieved this goal using a technique called solution-phase ligand exchange, which can adjust the surface chemistry of quantum dots to enhance the performance of electronic devices. Unlike traditional manufacturing methods that often leave cracked or uneven films, this solution-based process produces smooth and uniform coatings in just one step, making it highly suitable for large-scale production.

The devices produced exhibit exceptional performance: they have a response time to infrared light on the order of microseconds (in contrast, the blinking speed of the human eye is several hundred times slower) and are capable of detecting light signals as weak as nanowatts.

"What excites me is that we can modify a material that has long been considered difficult to use in practical devices, making it more competitive," said Shlok J. Paul, the lead author of the study and a graduate researcher. "Over time, this material has the potential to emit light deeper in the infrared spectrum, a task that very few materials can currently accomplish."

This study adds new content to the previous research conducted by the same group of principal investigators, who developed a novel transparent electrode using silver nanowires. These electrodes maintain high transparency to infrared light while efficiently collecting electrical signals, addressing an issue related to a component of infrared imaging systems.

Combining their early research on transparent electrodes, these advancements address two main components of infrared imaging systems. Quantum dots provide sensing capabilities that meet environmental requirements, while transparent electrodes are responsible for signal collection and processing.

This combination addresses the challenges of large-area infrared imaging arrays, which require high-performance detection over vast areas and the reading of signals from millions of independent detector pixels. The transparent electrode allows light to reach the quantum dot detectors while providing an electrical pathway for signal extraction.

Sahu stated, "Every infrared camera on Tesla or smartphones needs to have eco-friendly and cost-effective detectors. Our approach can help these technologies become more widely adopted."

In some measurements, its performance is still not as good as the best heavy metal detectors. However, researchers expect that ongoing advancements in quantum dot synthesis and device engineering can narrow this gap.