In the last issue, we talked about how the liquid crystal display works. Today we are talking about another technology, called OLED. So, how does the display work on organic light-emitting semiconductors – about this in today's issue!
The main difference between the OLED display and LCD is that in the second case, the pixels are highlighted, and in OLED they emit their own light. At the same time, the brightness of the OLED display can be controlled per-pixelly.
The OLED display consists of several very thin organic films enclosed between two conductors. A small voltage is applied to these conductors (2 to 8 volts) and causes the display to emit light and, as a result, display images. To create organic light-emitting diodes thin-film structures are used, consisting of layers of several polymers. One of them is called emission, because in it processes occur, leading to the emission of light waves. And the other layer is called conductive. To control each pixel of the OLED display, a control voltage must be applied to each of them. When the voltage is applied to the layers, the motion of the electrons begins. In the emission layer, the energy of the electrons changes when they meet other charges, and radiation appears in the visible spectrum of the waves.
In the active matrix for pixel control, thin-film transistors are used, which are arranged in the form of a matrix, as in LCD displays. By feeding a control signal to individual transistors, you can control specific pixels.
There are three schemes of color OLED-displays. The most common option and the most efficient use of energy is a standard three-color model, called a model with separate emitters. Three organic materials emit light from the base colors – red, green and blue.
The second option is to use three identical white emitters that emit light through the color filters, but this model loses the first option for energy efficiency.
In the third case, blue emitters and special luminescent materials are used to convert short-wave blue radiation into longer wavelengths, red and green.
In all versions, OLED displays provide good color rendering, high contrast and brightness, have less weight and dimensions compared to LCD-displays. Of the advantages also can be allocated low power consumption, which is directly proportional to the brightness and area of the luminescence. OLED displays do not burn the screen when the static image is displayed for a long time. In addition, the image is clearly visible from any angle (up to 180 degrees).
As for the flaws, the main problem with OLED displays is the short lifetime of diodes of some colors, which is on the order of 2-3 years. Especially it concerns the blue color. But if you use only white LEDs, then their lifespan reaches 100,000 hours. Another drawback of OLED displays is the high cost.
It is expected that OLED-displays can be replaced by more efficient and economical TMOS-displays (with an optical gate of time multiplexing). This technology uses the inertia of the retina of the human eye. Also there are developments of Organic TFT-displays – working on the technology of organic transistors.