Display device having a plurality of pixels each comprising sub-pixels
An organic light emitting diode (OLED) display device is described, the display device having a plurality of pixels each comprising at least two sub-pixels of different types, a first sub-pixel type comprising an OLED device including a first type of OLED material and a second sub-pixel type comprising an OLED device including a second type of OLED material, and wherein at least one of said first and second types of sub-pixel comprises a plurality of series-connected OLED devices. Employing series-connected sub-pixels where different types of OLED material are used for a display such as a color, active matrix OLED display facilitates balancing sub-pixel drive voltages and hence enables the production of display devices with improved efficiency.
1. An organic light emitting diode (OLED) display device, the display device having a plurality of pixels each comprising at least two sub-pixels of different types, a first sub-pixel type comprising an OLED device including a first type of OLED material and a second sub-pixel type comprising an OLED device including a second type of OLED material, wherein the OLED device including said first type of OLED material has a lower drive voltage than the OLED device including said second type of OLED material and a said pixel has a common power supply line for supplying power to said at least two sub-pixels, and wherein the first and second sub-pixel types comprise different number of series connected devices.
2. An OLED display device as claimed in claim 1 wherein each of said series connected devices of a given type has substantially the same light emissive area.
3. An OLED display device as claimed in claim 1 wherein said first and second types of OLED material have different peak emission wavelengths.
4. An OLED display device as claimed in claim 1 wherein a said pixel comprises three sub-pixels of different types, a said pixel including a third sub-pixel type comprising an OLED device including a third type of OLED material.
5. An OLED display device as claimed in claim 4 wherein at least two of said sub-pixel types comprise a plurality of series-connected OLED devices.
6. An OLED display device as claimed in claim 1 further comprising a drive transistor associated with each sub-pixel.
7. An OLED display device as claimed in claim 1 wherein said first type of OLED material comprises a fluorescent material.
8. An OLED display device as claimed in claim 7 wherein said second type of OLED material comprises a phosphorescent OLED material.
9. An OLED display device as claimed in claim 1 wherein said first type of OLED material comprises a polymer material.
10. An OLED display device as claimed in claim 9 wherein said second type of OLED material comprises a dendrimer OLED material or small molecule OLED material.
11. An active matrix color display incorporating the display device of claim 1 .