Today's infrared cameras are made by successively laying down multiple layers of semiconductors - a tricky and error-prone process that makes them too expensive to go into most consumer electronics.
The researchers instead turned to quantum dots - tiny nanoparticles just a few nanometers in size. At that scale they have odd properties that change depending on their size, which scientists can control by tuning the particle to the right size. In this case, quantum dots can be tuned to pick up wavelengths of infrared light.
This 'tunability' is important for cameras, because they need to pick up different parts of the infrared spectrum. "Collecting multiple wavelengths within the infrared gives you more spectral information - it's like adding color to black-and-white TV," said postdoctoral researcher Xin Tang, the first author. "Short-wave gives you textural and chemical composition information; mid-wave gives you temperature."
They tweaked the quantum dots so that they had a formula to detect short-wave infrared and one for mid-wave infrared. Then they laid both together on top of a silicon wafer.
The resulting camera performs extremely well and is much easier to produce, according to the researchers. "It's a very simple process," Tang said. "You take a beaker, inject a solution, inject a second solution, wait five to 10 minutes, and you have a new solution that can be easily fabricated into a functional device."
There are many potential uses for inexpensive infrared cameras, the scientists said, including autonomous vehicles, which rely on sensors to scan the road and surroundings. Infrared can detect heat signatures from living beings and see through fog or haze - a particuarly useful quality for the driverless car.
