PPI

Samsung Display has developed a 18.2" 2560x1440 202 PPI inkjet-printed OLED display, that features the highest current efficiency of any inkjet-printed OLED, with the brightness at 350 cd/m² (full white).

Samsung Display says that the high brightness was achieved by tuning the top-emission device structure with high performance soluble materials. The high pixel resolution was achieved by modulating the jetting waveform for ejecting ink drops and improving the drop placement accuracy by selecting the right ink formulations in terms of viscosities and surface energies.

In 2012, we first heard that eMagin is developing direct emission (or direct patterning, as the company calls it) OLED microdisplays. Fast forward into 2020, and the company is aiming to soon start producing such displays (it already launched its first such panel, see more below). In this article we'll look into the technology and the latest updates from eMagin.

All current OLED microdisplays on the market from all producers use a white OLED with color filter. This is a simple design, but it is wasteful in energy, as the filters block around 80% of the light, and in addition to achieve the white color one needs to use a blue OLED emitter (in addition to a yellow one, or red and green ones) - and blue is the least efficient color for OLED emission.

In January 2019 Taiwan-based INT Tech unveiled its proprietary glass-based high pixel density OLED technology, and the company now announced that its first prototype display was produced and successfully tested.

INT Tech's display is a 0.7" 2,300 PPI real RGB side-by-side AMOLED display. INT Tech says that its technology enables larger displays with higher brightness, lower power consumption and a wider color gamut compared to currently available OLED microdisplays which are produced on silicon.

Researchers from the Holst Center has applied spatial atomic layer deposition (sALD) to create both the semiconductor and dielectric layer in a thin-film transistor (TFT) Oxide-TFT (IGZO) display backplane - for the first time ever.

The researchers created a 200 PPI QVGA OLED display prototype on a thin PEN foil. This shows how TFTs can be produced in a low temperature process (below 200 degrees Celsius) using sALD on a cheap transparent plastic foil. The TFTs achieved a mobility of 8 cm²/V2 with channel lengths down to 1 um.