AMOLED Screens

Construction and Working:-

Let's consider OLED first. Each OLED consists of a cathode, an anode and an organic layer between them. The organic layer is divided into 2 parts – the emissive layer which is closer to the cathode and the conductive layer which is closer to the anode. These 2 layers can conduct electricity. When a voltage is applied to the electrodes (cathode and anode), the cathode gets charged negatively, while the anode gets charged positively. In other words, electrons flow and accumulate at the cathode. There is a depletion of electrons at the anode, causing it to be more positive. As a result of this, the emissive layer, which is closer to the cathode, also becomes negatively charged, with plenty of electrons. On the other hand the conductive layer, which is closer to the anode, becomes positively charged. An electron is a negative charge. When there is depletion of an electron, the absence of it, is said to be a positive charge or a hole. Hence a hole does not physically exist. It is just the absence of an electron.

This charging of the emissive and conductive layers, causes the excess electrons in the emissive layer to be attracted to the positively charged holes in the conductive layer. Hence, these electrons flow into the conductive layer from the emissive layer. They recombine with the holes in the conductive layer producing energy. The recombination happens closer to the emissive layer. The energy is in the form of visible light in the emissive layer. Different colour lights are produced by using appropriate organic material.

Active Matrix OLED has a similar set-up. The pixels are built on a platform that has a TFT (thin film transistor) circuit array. Each pixel has 2 TFTs associated with it. These TFTs take care of the charging and discharging of the set-up and also maintain the voltage level to create the current required. Depending on the current intensity, the light emitted will also vary in intensity.

Advantage over LCD screens:-

OLED and hence AMOLED screens too, do not require backlight, as they directly emit light themselves. Thus power consumption is much less compared to LCD displays (which require backlights for visibility in dim light conditions). The absence of the backlight set-up has one more advantage – OLED and AMOLED screens can be thinner than LCD screens. Moreover, the light emitted from OLED and AMOLED can be clearly seen from any angle. Thus, AMOLED screens offer clear images and colours when seen from an angle as well. The next advantage is that response times of OLED and AMOLED screens are faster than that of LCD screens. Therefore changing of frames in videos will be faster with OLED and AMOLED displays. OLED and AMOLED screens can also produce deeper black levels and thus have bright displays. This is because, for producing a black shade, the OLED and AMOLED simply will not glow or emit light at all.

The disadvantage of OLED and AMOLED screens is that, one has to be careful while handling them. Water can damage such displays easily. Although, they are rugged, they should not be bent beyond a certain point, which might result in intermittent display line failures. However these disadvantages seem less weighty than the advantages.

Many of the mobile phone makers like Nokia and Samsung have adopted AMOLED technology in their mobile phones. Samsung I7500 and Nokia N85 mobile phones are 2 examples.