Broadband photodetector material senses visible light to long-wave infrared, simplifying device design

A research team in South Korea has developed a next-generation sensor material capable of integrating the detection of multiple light wavelengths.

A joint research team led by Dr. Wooseok Song at the Korea Research Institute of Chemical Technology (KRICT) and Professor Dae Ho Yoon at Sungkyunkwan University successfully developed a new broadband photodetector material that can sense a wider range of wavelengths compared to existing commercial materials, and achieved cost-effective synthesis on a 6-inch wafer-scale substrate.

This research is published in ACS Nano.

Photodetectors are typically divided into different categories depending on the wavelength range they detect, serving applications in smart devices, security, environmental monitoring, and health care.

Until now, separate sensors for visible, near-infrared (NIR), mid-infrared (MWIR), and long-wave infrared (LWIR) were required. For example, autonomous vehicles or military drones need to mount multiple sensors for different functions. Broadband photodetectors, however, integrate multiple wavelength ranges into a single sensor.

Conventional broadband sensors based on two-dimensional (2D) materials could only detect from visible to NIR wavelengths, while MWIR and LWIR detection was limited, and their poor stability under humidity and temperature variations hindered outdoor or defense applications.

The newly developed broadband photodetector material detects the full spectrum from visible to LWIR and maintains stability even under high-temperature and high-humidity conditions. This allows product designs to be simplified and production costs reduced by replacing multiple sensors with a single integrated device.

For instance, an autonomous vehicle or military drone could integrate visible-light sensors (for daytime imaging and recognition), NIR sensors such as LiDAR (for distance measurement), and MWIR/LWIR sensors (for night-time human detection) into one.

The team utilized a topological crystalline insulator (SnSe₀.₉Te₀.₁), derived from the 2D semiconductor tin selenide (SnSe) with tellurium (Te) substitution.

As a quantum material, TCIs exhibit a narrow band gap, enabling detection of long-wavelength light such as MWIR and LWIR, while also maintaining high stability.

Unlike conventional 2D semiconductors that cannot detect low-energy photons due to a wide band gap, the TCI structure allows electrons to move freely on the surface states, enabling broadband and highly sensitive detection—including subtle LWIR thermal radiation such as that emitted by human fingers.

As a result, this new material achieves broadband detection over an ~8× wider range (0.5–9.6 μm), compared to conventional 2D semiconductors (0.4–1.2 μm). It is also thin, lightweight, and highly stable under high temperature, humidity, and even underwater conditions.

Another key advantage is the simplified and low-cost fabrication process.

While traditional TCI synthesis required expensive ultra-high-vacuum equipment such as molecular beam epitaxy (MBE), the research team designed SnSe₀.₉Te₀.₁ to retain topological properties while being less sensitive, enabling cost-efficient solution-based thermal decomposition synthesis. This allowed uniform production on a palm-sized 6-inch wafer, which is compatible with existing semiconductor processes, making it favorable for large-scale manufacturing.

The team is now extending this technology to 8-inch or larger wafers and integrating sensor arrays and circuits to develop complete sensor modules.

Dr. Wooseok Song explained, “This sensor can cover applications ranging from autonomous vehicles and military drones to smartwatches and home IoT security systems.”

KRICT President Young-Kuk Lee emphasized, “This breakthrough will mark a turning point in replacing expensive imported broadband sensors and usher in an era of high-performance, domestically produced broadband sensors.”