Fundamental Structure of OLED
OLED stands for Organic Light-emitting Diode and is based on a process whereby electrical energy is converted into light. Solar cells, for example, absorb light and generate electricity, but with OLED the exact opposite occurs. OLED displays are based on component devices containing organic electroluminescent material that emits light when stimulated by electricity.

An OLED component device consists of several layers of organic electroluminescent film with each layer measuring a mere 100nm. These layers are sandwiched between two electrodes. The electrodes create a flow of electrons and electron holes. These electrons and electron holes flow to the emissive layer (EML) inside the films and recombine. This activates the organic electroluminescent material in the EML to emit light. These OLED component devices are marked by high contrast, rapid response, a fully sealed structure and wide viewing angle.

Light-Emitting Mechanism
The organic electroluminescent film consists of HTL (Hole Transport Layer) + EML(Emissive Layer)+ ETL (Electron Transport Layer.) Two electrodes are placed on either side of the film. Voltage is applied to these electrodes and they send electrons (from the cathode) and electron holes (from the anode) into the organic electroluminescent film . The electrons and electron holes recombine in the presence of the EML's light-emitting molecules , and light is emitted .

The term OLED(Organic Light-emitting Diode)is used because electric current generates light and because it features typical diode properties and relationships of voltage and electric current.

Top Emission---Efficient Use of Organic Electroluminescent Light
With OLED panels, there are two methods of utilizing light produced by the organic layer---top emission and bottom emission. In bottom emission, which has a comparatively simpler manufacturing process, the structure causes light, generated by the organic material, to travel downward toward the TFT. However, the presence of opaque pixel driver circuits partially block and therefore limit the amount of light, reducing brightness. Therefore, this method is comparatively inefficient in terms of utilizing light. By contrast, with top emission (the method used by Sony), the structure causes light to travel to the "top" side where there are no pixel circuits to limit the light. This is a much more efficient means of utilizing the light produced by the organic material and this method offers lower power consumption and longer life.

Fully Stabilized Sealing Offers Greater Potential for Slimmer Panels
Organic electroluminescent materials are easily degraded by moisture and oxygen. If organic electroluminescent film is exposed to air, its functionality and performance rapidly decline. Therefore, organic electroluminescent films need to be completely sealed from the surrounding atmosphere. Previously, a metal cover was used for sealing, which meant that light could not penetrate the sealing side, and thus the bottom emission method was the only viable option. However, Sony enhanced the top emission method by using a resin-based adhesive agent to stabilize the sealing substrate by attaching it directly to the OLED substrate. Additionally, the elimination of the hollow section creates the potential for larger devices. Further, the sealing glass is not as thick, making it possible to manufacture larger panels. At the same time, utilizing plastic film sealing opens up the prospect of ultra-slim panels.

Microcavity Structure
In addition to the unique OLED panel structure described above, Sony's Super Top Emission technology (Fig. 4) utilizes a microcavity structure and color filters to simultaneously enhance color purity, attain higher contrast and achieve lower power consumption.

The microcavity structure utilizes light resonance effects between the two electrodes. Red, Green and Blue all have different light wavelengths. Therefore the thickness of the organic film corresponding to each color is adjusted to produce the spectral peak wavelength (the optimum light) for each color. Only light that possesses the same wavelength as the distance between the "cathode electrode semitransparent film" and the "anode electrode reflective film" resonates. Light wavelengths that do not match are weakened. As a result, the spectrum of the extracted light is sharpened while brightness and color purity are enhanced. This ensures the strongest light from each color.

In conventional panels, a circular polarizer (retardation film and polarizer) is installed on the panel surface to prevent the reflection of ambient light. However this structure also reduces the amount of electroluminescent light emitted by less than half. Sony rejected the circular polarizer and instead created a microcavity structure combined with color filters. This both prevents the reflection of ambient light and enhances color purity. The results are lower power consumption with longer life and advanced picture quality.

Figure 6 shows the effects of reducing ambient light achieved by the microcavity structure and the color filters. When the organic layer optical path length is matched to the wavelength of green electroluminescent light, the internally generated green light is strengthened, while the green component of the ambient reflected light is cut. At the same time, the color filter removes non-green colors from the ambient reflected light. High contrast can therefore be achieved without using a circular polarizer, and power consumption is reduced by half.
* This figure shows green as an example, but the same applies to red and blue.