What They Say
A group of researchers from CSOT in China published an open access article in Nature Communications explaining how they had used a ‘selective electrophoretic deposition (SEPD) technique’ to deposit QDs on a large area substrate with more than 1,000 pixels per inch. The dots could be selectively deposited and had a precisely controlled thickness, the group said.
The QDs QDs themselves tend to have surface charge makes them suitable for the process. The novel EPD process uses a high-accuracy microelectrode created by photolithography to rapidly (a few seconds) fabricate QD patterns only on selective polarity electrodes. The deposited QD films with controlled, uniform feature sizes down to 2?µm and precisely modulated thickness can be patterned into pixel array with arbitrary yet predefined shapes beyond 1,000 pixels per inch (PPI). The surface morphology, packing density, and refractive index of deposited QD films are tunable by changing the electric field, enabling the tailoring of the performance of QD devices and achieving higher luminous efficiency than conventional solution-processed methods.
The group peresented results of creating QD patterns with RGB QDs at densities from 252 to 1093 ppi.
As well as demonstrations using photo-luminescence, the group said that it the method ‘shows promise in fabricating EL devices’ and a proof of concept emissive display was made.
50 pages of additional information was published including a table comparing the methods for depositing QDs.
What We Think
This is an interesting paper – much of which is beyond my pay grade, but clearly the researchers have really done a lot of work to get to this point and the method certainly, on the face of it, looks attractive. The table highlights that there is a challenge to get a very uniform electric field and, just like the intractable issues of inkjet printing, those could be a barrier to commercialisation. Still, it’s interesting to see innovative approaches to the challenges of making large displays with this resolution. I don’t think this is the last we’ll hear of SEPD and I think I’ll set up a tag on the website for it. (BR)
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