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intro_oled [2026/06/05 16:36] – [Structure types] yusufabdillahintro_oled [2026/06/05 16:45] (current) – [Other topics] yusufabdillah
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-The characteristic of this structure is that light is directed from the emissive layer **towards the anode** and the substrate: they have to be **transparent** in the physics meaning if the term (i.e. not interact with a wave, and hence not absorb light rays). Usually, the transparent electrode is made of **ITO (indium-tin oxide)** and the substrate is made of **glass**.+The characteristic of this structure is that light is directed from the emissive layer **towards the anode** and the substrate: they have to be **transparent** in the physical sense of the term (i.e. not interact with a wave, and hence not absorb light rays). Usually, the transparent electrode is made of **ITO (indium-tin oxide)** and the substrate is made of **glass**.
  
-Because the emissive layer emits in all space direction, the cathode has to be made of a **reflective material** (e.g. silver) to redirect rays towards the anode. +Because the emissive layer emits light in all directions, the cathode has to be made of a **reflective material** (e.g. silver) to redirect rays towards the anode. 
  
-The main disadvantage of the bottom-emission structure is that light has to pass through the pixel control circuit (the TFT matrix in the case of an AMOLED) that cannot be fully transparent. This implies a lower quantity of light that can actually get out of the device. It is in this context that the top-emission structure emerged, to compensate for this drawback.+The main disadvantage of the bottom-emission structure is that light has to pass through the pixel control circuit (the TFT matrix in the case of an AMOLED) that cannot be fully transparent. This implies a lower amount of light that can actually get out of the device. It is in this context that the top-emission structure emerged, to compensate for this drawback.
  
 <figure center |bottom_emission_OLED> <figure center |bottom_emission_OLED>
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-In this structure, light is emitted from the emissive layer **towards the cathode**, it must therefore be transparent. Conversely, the **anode must be reflective** to redirect light towards the cathode. ITO is not a great fit for the cathode material due to technical constraints during the material deposition, and preferably a **thin-film silver** or **magnesium-silver alloys** is used. The cathode is however **semi-transparent** rather than transparent (some part of the incident rays are transmitted by the material and another part is reflected) which is not a problem if the material have **great transmittance** and **conductivity**. +In this structure, light is emitted from the emissive layer **towards the cathode**, it must therefore be transparent. Conversely, the **anode must be reflective** to redirect light towards the cathode. ITO is not a great fit for the cathode material due to technical constraints during the material deposition, and preferably a **thin-film silver** or **magnesium-silver alloys** is used. The cathode is however **semi-transparent** rather than transparent (some part of the incident rays are transmitted by the material and another part is reflected) which is not a problem if the material has **great transmittance** and **conductivity**. 
  
 <figure center |top_emission_OLED> <figure center |top_emission_OLED>
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-This structure has **two transparent electrodes**: it is a combination of both bottom- and top-emission structures. This helps obtaining **higher contrast levels** and make it particularly adapted for **outdoor devices**. +This structure has **two transparent electrodes**: it is a combination of both bottom- and top-emission structures. This helps obtaining **higher contrast levels** and makes it particularly suitable for **outdoor devices**. 
  
  
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 - **AMOLED (Active-Matrix OLED)** - **AMOLED (Active-Matrix OLED)**
  
-**AMOLEDs** include complete layers of cathode, organic components and anode. The layers of anode consist of **TFT (thin film transistors)** in parallel to form a matrix, which helps in switching each pixel to its on or off state as required hence, forming an image. When the pixels are not needed, they turn off or a black image on display occurs. This is least power consuming type and has quick refresh rates. They are best used in computer monitors, electronic signs or big TV screens. +**AMOLEDs** include complete layers of cathode, organic components, and anode. The layers of anode consist of **TFT (thin film transistors)** in parallel to form a matrix, which helps switch each pixel to its on or off state as required hence, forming an image. When the pixels are not needed, they turn off or a black image on display occurs. This is the least power-consuming type and has quick refresh rates. They are commonly used in computer monitors, electronic signs or big TV screens. 
 [([Q. Liu and T. Zhang, ‘Comparison between AMOLED and Traditional Display Technology and Application of AMOLED’, SID Symp. Dig. Tech. Pap., vol. 53, no. S1, pp. 1018–1021, 2022, doi: 10.1002/sdtp.16179.](https://www.researchgate.net/publication/364399984_P-1314_Comparison_between_AMOLED_and_Traditional_Display_Technology_and_Application_of_AMOLED))] [([Q. Liu and T. Zhang, ‘Comparison between AMOLED and Traditional Display Technology and Application of AMOLED’, SID Symp. Dig. Tech. Pap., vol. 53, no. S1, pp. 1018–1021, 2022, doi: 10.1002/sdtp.16179.](https://www.researchgate.net/publication/364399984_P-1314_Comparison_between_AMOLED_and_Traditional_Display_Technology_and_Application_of_AMOLED))]
  
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 **Types of rigidity: flexible vs. rigid OLED screens ** **Types of rigidity: flexible vs. rigid OLED screens **
  
-Flexible OLED based products aren’t always bendable or foldable  +Flexible OLED-based products aren’t always bendable or foldable  
-[(P. Samorì and V. Palermo, [Flexible Carbon-based Electronics](https://books.google.fr/books?id=c_x0DwAAQBAJ). John Wiley & Sons, 2018)]. Flexibility is used to provide the display with a non-traditional form factor, but it is then bonded to a rigid glass cover in the product. e.g.: some smartphones (Samsung Galaxy Note, LG G Flex), some smartwatches (Apple Watch, LG watch urbane). 1st smartphone using AMOLED flexible tehcnology = 2013. +[(P. Samorì and V. Palermo, [Flexible Carbon-based Electronics](https://books.google.fr/books?id=c_x0DwAAQBAJ). John Wiley & Sons, 2018)]. Flexibility is used to provide the display with a non-traditional form factor, but it is then bonded to a rigid glass cover in the product. e.g.: some smartphones (Samsung Galaxy Note, LG G Flex), some smartwatches (Apple Watch, LG watch urbane). The first smartphone using flexible AMOLED technology was introduced in 2013. 
  
-The difference in the manufacturing of flexible and rigid OLEDs remains in two processes steps: substrate and encapsulation ([[screen_manufacturing|check this page]] for more information).+The difference in the manufacturing of flexible and rigid OLEDs lies in two processes steps: substrate and encapsulation ([[screen_manufacturing|check this page]] for more information).