Compact and efficient RGB to RGBW data conversion method and its application in OLED microdisplays

In many electronic information displays, a colour pixel comprises three spatially distinct sub‐pixels containing red, green and blue (RGB) colour filters. The option of adding a fourth white (W) sub‐pixel that allows light to pass through unfiltered can significantly improve the optical efficiency of the pixel that, in turn, increases the power efficiency of the display. Such a display is called an RGBW display, and the required transformation of data format from incoming RGB to pixel RGBW is termed as “RGB to RGBW conversion.” This paper reports a method of RGB to RGBW conversion that is highly compact and efficient in terms of system resources while retaining image quality. It processes incoming data through a new colour space conversion algorithm in order to reduce the average power consumption with no noticeable visual artefacts. We explain the method and demonstrate its cost‐effective and power‐effective implementation for the specific case of an organic light emitting diode microdisplay.     

Micro‐cavity design of bottom‐emitting AMOLED with white OLED and RGBW color filters for 100% color gamut

Abstract— Two optical structures used for a bottom‐emitting white organic light‐emitting diode (OLED) is reported. An RGBW color system was employed because of its high efficiency. For red, green, and blue (RGB) subpixels, the cavity resonance was enhanced by the use of a dielectric mirror, and for the white (W) subpixel, the mirror was removed. The optical length of the cavities was controlled by two different ways: by the thickness of the dielectric filter on top of the mirror or by the angle of oblique emission. With both methods, active‐matrix OLEDs (AMOLEDs) that reproduced a color gamut exceeding 100% of the NTSC (National Television System Committee) standard were fabricated. More importantly, the transmission of a white OLED through R/G/B color filters was significantly higher (up to 50%) than that of a conventional structure not employing a mirror, while at the same time as the color gamut increased from ～75 to ～100% NTSC.     

Organic polymer thick film light emitting diodes (PTF-OLED)

A guest–host approach was used to fabricate a one-layer organic light emitting diode (OLED). The thick film ink approach allows the two-dimensional OLED to be processed using traditional methods such as silk-screen printing. The I–V–L characteristics of the polymer thick film (PTF)-OLED were studied as a function of the device chemical compositions and physical configurations. Different polymers, hole and electron transporters, and emitters at different weight ratios were studied for its composition dependence. Device configuration also plays a significant role on its overall performance. Dependence on film thickness, electrode type, and the usage of additional charge injection layers were also investigated. The simplified one-layer device allows a straightforward interpretation for the charge-transport and recombination phenomena which shed light for its future improvement.     

White stacked OLED with 38 lm/W and 100,000‐hour lifetime at 1000 cd/m2 for display and lighting applications

Abstract— The three critical parameters in determining the commercial success of organic light‐emitting diodes (OLEDs), both in display and lighting applications, are power efficiency, lifetime, and price competitiveness. PIN technology is widely considered as the preferred way to maximize power efficiency and lifetime. Here, a high‐efficiency and long‐lifetime white‐light‐emitting diode, which has been realized by stacking a blue‐fluorescent emission unit together with green‐ and red‐phosphorescent emission units, is reported. Proprietary materials have been used in transport layers of each emission unit, which significantly improves the power efficiency and stability. The power efficiency at 1000 cd/m² is 38 lm/W with CIE color coordinates of (0.43, 0.44) and a color‐rendering index (CRI) of 90. An extrapolated lifetime at an initial luminance of 1000 cd/m² is above 100,000 hours, which fulfils the specifications for most applications. The emission color can also be easily tuned towards the equal‐energy white for display applications by selecting emitting materials and varying the transport‐layer cavities.