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Optoelectronics/Displays??

Cree patents hybrid LED-OLED tech to generate white light

Posted: 27 Oct 2014 ?? ?Print Version ?Bookmark and Share

Keywords:Cree? LED? OLED? luminaire? patent?

Cree has gained approval for a patent application that integrates LED with OLED technology to generate white light. Granted by the United States Patent and Trademark Office (USPTO), the hybrid LED-OLED patent application could be an early sign of Cree's plan to change its product strategy.

The patent application describes a solid state lighting system and/or a luminaire that can generate white light by combining OLED lights with another solid state emitter, for instance a conventional LED. The OLED and other emitters are arranged spaced apart in a mixing chamber of the luminaire to cut colour hot spots that can be found in typical LED emitters when using two different colours in close proximity in a luminaire.

Cree offers four types of examples for how the proposed hybrid OLED-LED technology would function. In the first case the solid state emitter is a conventional LED packaged with phosphor to emit blue-shifted yellow light (BSY) as the first colour, while the OLED is operable to emit red light as the second colour of light. The two are combined to create white light with a colour rendering index (CRI) of 90. In some cases, the diffuser is placed adjacent to the substantially transparent substrate.

In the second example, the solid state emitters that emit the first colour of light are phosphor free LEDs that are used in combination with a remote phosphor. The remote phosphor is placed near the OLED substrate. LEDs that emit the first colour of light might be blue light, and the remote phosphor is used in combination with the LEDs to produce BSY light mixed with red light from OLED at the opening of the mixing chamber. A dichoric mirror is employed in the opening of the mixing chamber, and placed between the substrate and remote phosphor, for example, a red dichroic mirror. The mirror prevents absorption of the red light by the mixing chamber, and devices or structures within.

The third example, the lighting system is based on two types of emitters used to make a luminaire by providing the mixing chamber with the plurality of emitters to emit light of the first wavelength, whether these are BSY emitters using a local phosphor, blue emitters, or other colour emitting LEDs designed to work with a remote phosphor. The OLED on the transparent substrate is installed at the opening through which light exits the mixing chamber and the eventually the luminaire. The mixing chamber is connected to a heat sink and power connections are provided to all emitters, the finished luminaire may include a power supply or powered by a DC power system.

In the other example, the light from the blue-emitting LEDs in a luminaire has a dominant wavelength from 435-490nm, the light from the OLED has a dominant wavelength from 600-640nm and the light from the phosphor has a dominant wavelength from 540-585nm. In some examples, the light from the blue-emitting LEDs in a luminaire has a dominant wavelength from 440-480nm, the light from the OLED has a dominant wavelength from 605-630nm and the light from the phosphor has a dominant wavelength from 560-580nm.

- Paul Buckley
??EE Times Europe





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