Quantum dots: time of growth and change: Page 2 of 6

July 27, 2018 //By Dr Khasha Ghaffarzadeh
Quantum dots: time of growth and change
Quantum dots (QDs) are no longer a young technology. Even their commercialization process is not new since the pioneering companies were formed in the 2001-2005 period. The QDs are also not commercially novice: they have been employed in LCD displays as remote phosphors for several years.  

This gap is hard to rapidly fill because controlling the shape and size monodispersity of InP particles is challenging.   QDs have also become more stable. This has already relaxed barrier requirements in film type implementation and is anticipated to continue to do so. This trend therefore leads to simpler and lower cost barrier films. Efforts to improve production either via larger scales or via innovative processes such as low-temperature molecular seedings, continuous reactions in microcapillaries or one-pot synthesis process all seek to lower per Kg production costs.

Increased QD brightness will also result in lower per sqm consumption. All these factors are driving down total QD implementation costs.  In turn, this is opening new pricing strategies to display makers. This has led to an interesting dynamic in which some, including many in China, are expanding product range to cover a spectrum of prices, whereas others are struggling to maintain the high-priced ultra-premium aura of QD displays in defiance of new cost realities.

 

Quantum dots: Advanced material innovators' dream

InP chemistry is not the only alternative to Cd QDs. There is also the perovskite QDs (PeQDs). These QDs offers emission wavelength (color) control via size and composition. For example, varying the X from iodide to bromide and chloride in organic MPbX or inorganic CsPbX shifts the emission from red to green and blue.   PeQDs also exhibit a higher tolerance of disorder, making it easier to achieve narrowband emission. They are however still a young technology with significant drawbacks. The red PeQDs are chemically highly stable, restricting the choice mainly to inorganic green today (CsPbBr3) which gives <20nm FWHM.

As such, their future, at least in the medium term, will likely be hybrid with QDs used in conjunction with red phosphor or non-perovskite QDs. The work on materials does not end with this transition away from Cd QDs. In fact, the opposite: it is just entering an exciting time with many directions of development. Indeed, further material developments will dictate the fate of various QD implementation methods in displays.


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