LCDs with Quantum Dots are often seen as an alternative to OLED displays at a lower cost. The technology has been used for some years now (for example, by Sony) and is often marketed under a specific name for each brand. Nevertheless, quantum dots can provide a better color reproduction for LCDs, so far an inherent advantage of OLED displays.
Source: Sigma Aldrich
The advantage of quantum dots is that they are easily tuned to any desired color, as the emissive wavelength is only a function of the particle size. While quantum dots can be photoluminescent as well as electroluminescent, in today’s display application they are used as photoluminescent materials, as the excitation is done by a blue LED, that also provides the blue primary.
In a recent article, IHS DisplaySearch points out that the main reason for the slow adoption into consumer devices are the relatively high prices for quantum dot materials. The article quotes a cost of over $100 for a quantum dot sheet used in a 55″ TV. While this is more than a standard backlight, and makes QD technology a pricier option than LCD, it is still cheaper than OLED. DisplaySearch has seen a decrease in price in recent months, with some solutions falling below the $100 mark. Still, it believes that this is not enough to increase QD TV set sales into the millions of units as some suggest.
On the other hand many QD solutions are still using cadmium-based materials that require an exemption from many environmental regulations such as ROHS. While such exemptions have been granted, the use of heavy metals like cadmium are not easy to market, especially with cadmium-free alternatives available in the market.
Quantum Materials recently announced that it has started shipping Cd free QD materials to select customers. However, heavy metal free quantum dots are also available from other companies.
As DisplaySearch points out, at the moment quantum dot solutions are achieving lower emission efficiency than standard LCD. This disadvantage seems to be even more pronounced for heavy metal free solutions, requiring more LEDs. Of course, this also adds to the cost disadvantage. – Norbert Hildebrand
