Quantum Dots in Displays Get a New Tool

New method for measuring the spectral properties of quantum dots should improve manufacturing processes

2 min read
Quantum Dots in Displays Get a New Tool

Quantum dots are beginning to realize their promise for enabling the next generation of  computer displays and TVs. Just a few weeks ago, Sony put its LCD displays enabled by quantum dots provided by Massachusetts-based QD Vision on the market. And the partnership between California-based Nanosys Inc and 3M to market its Quantum Dot Enhancement Film (QDEF) technology should be on store shelves soon.

The fact that quantum dot technology has made it to market indicates just how far the technology has progressed. However, this is just their first introduction into the market so we should expect further refinements to the technology.

Some of those refinements are already in the offing. Researchers at the Massachusetts Institute of Technology say that they've developed a method that should serve to optimize quantum dots for display applications. 

The newly developed method--dubbed photon-correlation Fourier spectroscopy in solution—makes it possible to obtain the spectral properties of single particles in large groups. Up until now, if you wanted to get the spectral properties of single particles you had to look at them individually. With this new method it is possible to attain that data while looking at billions of particles at the same time.

The method, which was published in the journal Nature Chemistry ("Direct probe of spectral inhomogeneity reveals synthetic tunability of single-nanocrystal spectral line widths"),  starts by shining a laser into the quantum dots and then measuring the light that is emitted from the dots at very short time scales. This allows for dots that are not very far apart in space to be differentiated in time. Once the measurements are collected, it becomes possible to compare pairs of photons emitted by individual particles. This in itself does not provide the absolute color of particular particles, but it does allow for a statistical measure of the collection of quantum dots.

“We get the average single-particle line width in the solution, without any selection bias,” said Jian Cui, one of the authors of the paper, in a press release.

The method should make it possible to determine the quality of each quantum dot production method, serving as a kind of quality control check. This will also lead to being able to fine tune the production processes so that particular quantum dots can be synthesized for various applications.

The method has already determined that quantum dots synthesized from cadmium selenide, which are now widely used, do produce very pure colors. But it has also shown that indium phosphide is intrinsically suited for producing pure colors.

All of this should provide a useful tool in refining and improving the technology of quantum dots in displays.

Photo: Laren Aleza Kaye/MIT

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Digging Into the New QD-OLED TVs

Formerly rival technologies have come together in Samsung displays

5 min read
Television screen displaying closeup of crystals

Sony's A95K televisions incorporate Samsung's new QD-OLED display technology.

Sony
Blue
Televisions and computer monitors with QD-OLED displays are now on store shelves. The image quality is—as expected—impressive, with amazing black levels, wide viewing angles, a broad color gamut, and high brightness. The products include:

All these products use display panels manufactured by Samsung but have their own unique display assembly, operating system, and electronics.

I took apart a 55-inch Samsung S95B to learn just how these new displays are put together (destroying it in the process). I found an extremely thin OLED backplane that generates blue light with an equally thin QD color-converting structure that completes the optical stack. I used a UV light source, a microscope, and a spectrometer to learn a lot about how these displays work.

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