In a groundbreaking development, researchers from ICFO and Qurv have collaborated to fabricate a high-performance shortwave infrared (SWIR) image sensor based on non-toxic colloidal quantum dots. Their study, recently published in Nature Photonics, introduces a novel method for synthesizing functional, high-quality quantum dots compatible with complementary metal-oxide-semiconductor (CMOS) technology.

Figure 1. Non-Toxic Quantum Dots Sample and The Fabricated Photodevices. (Credit: ICFO)

Figure 1 shows Yongjie Wang (left) and Julian Schreier (right) holding non-toxic quantum dots sample and the fabricated photodevices.

The Potential of SWIR Technology

Shortwave infrared (SWIR) light, invisible to the human eye, holds immense potential for applications in service robotics, automotive, and consumer electronics. SWIR-sensitive image sensors can operate reliably under challenging conditions such as bright sunlight, fog, haze, and smoke. Additionally, the SWIR range offers eye-safe illumination and the ability to detect material properties through molecular imaging.

Overcoming Roadblocks with Quantum Dots

While colloidal quantum dots (CQDs) present a promising platform for SWIR image sensors, traditional heavy-metal-containing quantum dots face regulatory challenges due to substances like lead and mercury. The researchers focused on developing non-toxic colloidal quantum dots, specifically phosphine-free silver telluride (Ag2Te) quantum dots, to address these concerns and pave the way for mass-market applications.

Synthesis Breakthrough

During their exploration of silver bismuth telluride (AgBiTe2) nanocrystals, the team serendipitously discovered silver telluride (Ag2Te) as a by-product with strong quantum confined absorption properties. Recognizing its potential for SWIR photodetectors, the researchers devised a new process to synthesize phosphine-free silver telluride quantum dots, achieving well-controlled size distribution and excitonic peaks over an unprecedented range.

Laboratory-Scale Success

After fabricating phosphine-free quantum dots, the researchers faced the challenge of integrating them into a laboratory-scale photodetector on an Indium Tin Oxide (ITO)-coated glass substrate. Overcoming initial performance issues, they enhanced the SWIR photodiode's capabilities through strategic redesign, achieving a spectral range from 350nm to 1600nm and outstanding performance metrics.

Towards Mass-Market SWIR Image Sensors

Encouraged by the success of the heavy-metal-free quantum dot photodetector, the researchers collaborated with Qurv to demonstrate its potential in constructing a SWIR image sensor. The integrated photodiode, along with a CMOS-based read-out integrated circuit (ROIC) focal plane array (FPA), marked a significant milestone—a non-toxic, room temperature-operating SWIR quantum dot-based image sensor.

Applications and Future Directions

The implications of this breakthrough extend to diverse applications, including improved vision systems for the automotive industry, long-range light detection and ranging (LiDAR), and advancements in augmented reality and virtual reality. Moving forward, the researchers aim to enhance photodiode performance by engineering device layers and exploring new surface chemistries for Ag2Te quantum dots, ensuring their viability for market integration. The successful development of non-toxic SWIR image sensors opens doors to safer and more accessible technology across various industries.

Source: ICFO

Cite this article:

Hana M (2023), Non-Toxic Quantum Dot Technology Powers Breakthrough in SWIR Image Sensors, AnaTechMaz, pp. 136