In general, WOLED involves depositing many layers. The RGB color effect comes from color filters. As such, the system has low efficiency (filters waste 2/3 of light). In turn, this demands higher brightness, leading to harsher drive conditions and shorter lifetimes. The primary advantage of this approach is that it can be scaled to large areas. This is why it is the technology of choice for OLED TVs. Reducing production cost however thus far has proven complicated although steady progress is being made.
Both approaches rely upon evaporated materials. An immediate question then is why is printing not being used. This way direct RGB patterning over large areas with high material utilization could be achieved. In the remainder of this article we will cover the progress and prospects of printing OLEDs.
Printed OLED displays: are the materials good enough yet?
Developing solution processible OLED materials has not been easy. At first, only polymeric materials could be solubilized. In the early generations, this would give very low EQEs and lifetimes. With time, polymer/small molecule and even solution-processible small molecule OLED materials were developed. The polymeric-only products also improved tremendously.
The upshot is that today after three decades of global research and development effort solution-processible OLEDs are becoming a viable proposition. Finally, the performance gap in Cd/A between leading printable OLEDs and commercial evaporated ones has been nearly bridged. This is true for green and red materials, and it is also the case for the blue with appropriate colour coordinates commonly used in displays.