Leading U.S. LED manufacturer Cree’s patent application which integrates LED with OLED technology to generate white light was recently approved by the United States Patent and Trademark Office (USPTO).

Cree’s OLED application is a significant development in the lighting industry, and might be signaling the early signs of the company’s changing product strategy.

In the summary of the patent application, Cree explained the new invention provides solid state lighting system and or a luminaire to 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 minimize color hot spots that can be found in typical LED emitters when using two different colors in close proximity in a luminaire.

A drawing of Cree's latest OLED-LED patent. (Image Courtesy of USPTO)

Cree offers four types of embodiments for this new OLED-LED technology. 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 color, while the OLED is operable to emit red light as the second color of light. The two are combined to create white light with a Color Rendering Index (CRI) of 90. In some cases, the diffuser is placed adjacent to the substantially transparent substrate.

In the second embodiment, the solid state emitters that emit the first color 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 color 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.

In another 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 color 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 last embodiment, the light from the blue-emitting LEDs in a luminaire has a dominant wavelength from 435 to 490 nm, the light from the OLED has a dominant wavelength from 600 to 640 nm and the light from the phosphor has a dominant wavelength from 540 to 585 nm. In some embodiments, the light from the blue-emitting LEDs in a luminaire has a dominant wavelength from 440 to 480 nm, the light from the OLED has a dominant wavelength from 605 to 630 nm and the light from the phosphor has a dominant wavelength from 560 to 580 nm.

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