Note in the lifetime data shown in figure 2 that the vertical axis is the time to reach 50% of the initial luminance, a common metric for determining commercial viability. This data is only at 100 nits, a level too low for most applications, however, to be fair, most groups report results at this level so it makes for better comparison. A more typical luminance level of 500 nits is more representative, but lifetime degrade much more quickly at this level – “and not in a linear way,” says Hartlove.
Hartlove didn’t say what the lifetime might be at elevated luminance levels but he references TADF developments for OLEDs where blue lifetimes are in the 5-30 hour range for higher luminance levels. He thinks their team can get to this level in about a year as well.
Nanosys is focused on developing a blue ELQD composed of a ZnTeSe alloy that allows for blue emission in the 450-460 nm range. InP-based QD can be pushed down to 460nm but with very low quantum yield (~40%). ZnSe quantum dots can be pushed upward to maybe 450 but with a similar low quantum yield. By building a quantum dot with a little Tellurium in the ZnSe core, transitioning to ZnSe and then to ZnS, Nanosys can achieve blue light at 451nm with 80% quantum yield and a FWHM of 21 nm – all very acceptable values.