The team also investigated quantum yield vs. shell size when the QD solution was assembled into a device to form a QD film (QDs in solid form). Fortunately, these two maximum occurred at a similar shell thickness. The film quantum yield is an indicator of how efficient the ELQDs can be in a closed packed format (like in a ELQD device) . These results were positive as well suggesting it is the device structure, not the ELQD materials that are the limiting factor in device EQE.
Similar studies were then done on green and blue ELQDs to deliver the EQE results summarized in figure 3 (red/green/blue at 16.9%/15.6%/12.4%).
Hartlove sees ELQD materials reaching commercial viability for red, green and blue in the 2022 time frame. Once the materials are ready, someone will need to build a factory to start to make actual ELQD-based products. IoT indicator type displays might be one of the first applications, for example, but such products will likely appear after 2022, Hartlove wanted to make clear.
Initial products will have to find niche applications where other display technology may not be as competitive, so smaller, sunlight readable may be one good focus area. But Hartlove also sees the need for these to be very inexpensive, which is why they are focused on solution-based processing which offers this potential. In addition, the capex for a solution-processing factory will be substantially less (millions) compared to an OLED of LCD fab (billions).
It is a long way to get there from where we are today, and I think Hartlove is being too optimistic, but he has a better view of developments than I do. We will see.
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