Universal Display files for hybrid OLED display patent
Universal Display (OLED) has filed a patent application for a hybrid OLED display that uses typical OLED materials for red, green, and yellow sub-pixels, and uses a micro-LED for generating blue. The pixel arrangement, as shown below, is one of a number specified in the application, but the concept of importance is the addition of the micro-LED, which, in the diagram below, represents a source of blue light, providing the requisite RGB display.
The use of a micro-LED in this case would seem to be as a substitution for a fluorescent blue OLED emissive material, which itself is a substitute for a blue phosphorescent emitter. Currently, deep blue phosphorescent emitters have lifetimes too short to be effective in most consumer devices, and as such fluorescent emitters have been used in their place. Unfortunately fluorescent emitters have far less of an emissive output than phosphorescent materials, leading to trade-offs, higher power consumption, and less optimal displays, or, in this case, the use of a secondary inorganic device to make up the output shortfall.
Micro-LEDs are being touted as a possible solution to the expensive and IP protected heavy-metal based phosphorescent emitters that are commonly used in OLED displays, however there remain a number of issues currently limiting their use. As the LEDs are microscopic (the tri-color micro-LED used in Sony’s (SNE) CLEDIS™ technology is .003mm2 or 4.65-6”), they are hard to place accurately, which is essential for consumer displays, and yields are relatively low compared to typical OLED metal mask deposition, which could cause dead pixels in such a display. Micro-LEDs also have issues with color purity, and while only a single color is being utilized in the IP herein, lessening the possible problems, color filters or other means of controlling the overall color balance of the display could be needed.
That said, the idea of a hybrid OLED display does make sense as an interim solution to the fact that deep blue OLED materials have yet to be fabricated for commercial displays. New techniques for micro-LED placement, such as directly printing the micro-LED in situ, are being developed, and should the development of blue phosphorescent material continue to elude display material suppliers, such a hybrid device may be an alternative solution.
The use of a micro-LED in this case would seem to be as a substitution for a fluorescent blue OLED emissive material, which itself is a substitute for a blue phosphorescent emitter. Currently, deep blue phosphorescent emitters have lifetimes too short to be effective in most consumer devices, and as such fluorescent emitters have been used in their place. Unfortunately fluorescent emitters have far less of an emissive output than phosphorescent materials, leading to trade-offs, higher power consumption, and less optimal displays, or, in this case, the use of a secondary inorganic device to make up the output shortfall.
Micro-LEDs are being touted as a possible solution to the expensive and IP protected heavy-metal based phosphorescent emitters that are commonly used in OLED displays, however there remain a number of issues currently limiting their use. As the LEDs are microscopic (the tri-color micro-LED used in Sony’s (SNE) CLEDIS™ technology is .003mm2 or 4.65-6”), they are hard to place accurately, which is essential for consumer displays, and yields are relatively low compared to typical OLED metal mask deposition, which could cause dead pixels in such a display. Micro-LEDs also have issues with color purity, and while only a single color is being utilized in the IP herein, lessening the possible problems, color filters or other means of controlling the overall color balance of the display could be needed.
That said, the idea of a hybrid OLED display does make sense as an interim solution to the fact that deep blue OLED materials have yet to be fabricated for commercial displays. New techniques for micro-LED placement, such as directly printing the micro-LED in situ, are being developed, and should the development of blue phosphorescent material continue to elude display material suppliers, such a hybrid device may be an alternative solution.
UDC 'Hybrid' OLED pixel arrangement - Source: US Patent Office
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