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The State-of-the Art in IJP of OLEDs and QDs
 
This article appeared in Display Daily and has been modified by OLED-A for purposes of brevity and accuracy
 
Inkjet printing is used in the deposition of the organic layer in multi-layer thin-film encapsulation. Here, inkjet printed organics act as buffer layers separating PECVD-deposited inorganic layers. This is shown below. This is already an established process.

​The printing of the emissive RGB layers is more challenging. Polymeric solution-processed materials show performance levels that are almost on a par with evaporated small molecule emitters. The following charts compare printed OLED performance vs. evaporated materials (as of Q121) for red and green. The bottom right chart is from 2020 (Samsung) and compares evaporated vs printed blue while factoring in color coordinates. Here, TE and BE denote top and bottom emission, respectively. The three benchmarking charts- update as of Q1 2021- benchmark the performance levels for printed red, green, and blue vs evaporated versions. The performance gaps have now been largely bridged, paving the way for adoption without too much performance penalty. The lifetime, especially blue, needs further refinement as does the color point.

​The image below simply showcases some examples of inkjet printed OLED displays. JOLED is making OLED monitors some manufacturing. 

​In Samsung’s QD-OLED manufacturing process, multiple (4) blue layer stacks are vacuum deposited and the diver supplies 4x the voltage of a single layer, which is converted is converted to a standard current across each layer, generating higher luminance at the same current. The downside is the higher driving voltage, which increases the driver power consumption. Red and green, narrowband quantum dots (QDs) are then inkjet printed on each pixel, acting as a color converter. This approach provides a learning experience on the fully printed materials. 
 
BOE showed a 55-inch fully inkjet printed AMQLED (May 2021), but the manufacturing process is still being developed:

• Non-Cd containing QDs need to improve the EQE and lifetime,
• Better blue compositions need to be formulated,
• Stack materials including transport layers need to be advanced and optimized,
• Suitable device architecture developed 

 
Emissive QD material has lifetimes that are orders of magnitude lower than what is needed for a commercial product.