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Nanoelectronics: Basic Concepts, Approaches, and Applications
Published in Rakesh K. Sindhu, Mansi Chitkara, Inderjeet Singh Sandhu, Nanotechnology, 2021
Balwinder Kaur, Radhika Marwaha, Subhash Chand, Balraj Saini
People are experiencing a serious shortage of energy resources due to the increasing population and the consumption of a large amount of energy. Many researches have been performed to achieve efficient and low-energy light sources. Inorganic LEDs and organic light-emitting diodes (OLEDs) are the result of these continuous efforts to achieve solid-state light source [6]. The use of polymers and organic molecules as emissive layers to improve the characteristics of LEDs is the latest research in this area. The OLEDs display flexibility (tendency to deposit on plastic substrate), very thin displays, and transparency. An OLED is constructed by introducing a thin film of carbon-based material between an electron-emitting cathode and an electron-removing side anode, thereby considering one of electrodes transparent. The thin film of organic material called emitter is electroluminescent; it emits light upon excitation using electric current. The organic materials have conductivity between the conductors and insulators, so they behave like organic semiconductors. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) behave like valence band and conduction band. OLEDs have advantage over both LCDs and LEDs for being a thinner, lighter, more flexible, and brighter substrate.
Real-Time Alarm Clock Using Arduino
Published in Anudeep Juluru, Shriram K. Vasudevan, T. S. Murugesh, fied!, 2023
Anudeep Juluru, Shriram K. Vasudevan, T. S. Murugesh
OLEDs are generally more power-efficient compared to LCDs. OLEDs consume power depending on the content displayed on the screen whereas LCDs consume almost the same power irrespective of the content displayed on the screen. When displaying content with more black colour, OLEDs consume the least power as they need to just switch OFF the pixels at the places where the content is black. But, when displaying content with more white colour, OLEDs require more power as they need to switch ON most of the pixels whereas LCDs consume constant power irrespective of the content as it uses the same backlight for any type of content. Each pixel in an OLED has an organic component whereas pixels in LCD don’t. So, the life of OLEDs tends to be low compared to LCDs.
Vapor-Deposited Organic Light-Emitting Devices
Published in Zhigang Rick Li, Organic Light-Emitting Materials and Devices, 2017
One of the most obvious markets for thin-film vapor-deposited organic materials is in flat-panel displays [135], a market currently dominated by LCDs. During the last two decades, a great improvement in the lifetime and efficiency of OLEDs has been achieved. Today, OLED displays can be found in many applications, such as automobile stereos, mobile phones, digital cameras, and TVs. However, to exploit the advantages of the technology fully, it is necessary to pattern the OLEDs to form monochrome, or more preferentially, full-color displays. This section will consider the difficulties involved in addressing such displays (either passively or actively) and the variety of patterning methods that can be used to produce full-color displays.
Rising advancements in the application of PEDOT:PSS as a prosperous transparent and flexible electrode material for solution-processed organic electronics
Published in Journal of Information Display, 2020
Gunel Huseynova, Yong Hyun Kim, Jae-Hyun Lee, Jonghee Lee
OLEDs are flat self-light-emitting optoelectronic devices commonly applied for display and solid-state lighting technologies [11,33,65]. The simple structure of OLEDs consists of multilayers formed from organic materials functioning as an HTL, a light-emitting active layer, and an electron transport layer (ETL) stacked between two transparent and reflective electrodes called ‘anode’ and ‘cathode,’ respectively [33]. The main parameters defining the efficiency of OLED devices include the external quantum efficiency (EQE), turn-on voltage (VT), current density, current efficiency, power efficiency, color quality, and lifetime [33,66]. OLEDs are ultra-thin, ultra-light, flexible, and simple in design, as well as suitable for large-area electronics [11]. OLED displays are more efficient than liquid crystal displays (LCDs), and they deliver better image quality for lower power consumption. In addition, they do not require a backlight, as LCDs do [85]. OLEDs can also be a safe and excellent light source. They are both transparent and color-tuneable [86]. Although the first practical OLED appeared a little more than 30 years ago, the flexible OLEDs have been on the market for many years, and are the important components for the realization of the future flexible, wearable, foldable, and even biodegradable optoelectronic applications [85–87].
DFT-based study of the impact of transition metal coordination on the charge transport and nonlinear optical (NLO) properties of 2-{[5-(4-nitrophenyl)-1,3,4-thiadiazol-2-ylimino]methyl}phenol
Published in Molecular Physics, 2019
Christelle Herliette Atchialefack Alongamo, Nyiang Kennet Nkungli, Julius Numbonui Ghogomu
An OLED is a device component which emits light when an external voltage is applied. It is made up of an emissive layer (EL) comprised of a film of organic compounds, a hole-transport layer (HTL) and an electron-transport layer (ETL), all of which are situated between two electrodes [4]. For the HTL materials, properties such as efficient hole injection and high hole mobility are necessary for effective delivery of charge carriers towards the emissive or active layer [3,5]. Other important properties of an HTL material are: an appropriate HOMO energy level (5.4 eV) to ensure a low potential barrier for hole injection from the anode into the EL, and a suitable LUMO energy level to block electron injection from the EL to the HTL [3]. One of the most commonly used hole-transport materials is N,N′-diphenyl-N,N′-bis(3-methylphenyl)(1,1′-biphenyl)-4,4′-diamine (TPD) [5]. For a substantially enhanced OLED performance, the ETL material should possess the following qualities: suitable Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energy levels to allow minimisation of the potential barrier for electron injection, low turn-on/operating voltage and effective hole blocking ability [3]. On the other hand, tris(8-hydroxyquinolinato)aluminium (Alq3) is the commonest material that is used for the electron-transport layer [5].
Recent progress of organic light-emitting diode microdisplays for augmented reality/virtual reality applications
Published in Journal of Information Display, 2022
OLED microdisplays have been used in various electronic devices such as TVs, mobile phones, tablets, laptops, and automotive displays due to their fast response time, small thickness, light weight, high contrast ratio, rich colors, and small form factor. Because OLED microdisplays have superior performance compared with LCoS and DMD microdisplays, many AR/VR devices use OLED microdisplays [1,2]. However, even though OLED microdisplays have been released commercially, they need much higher luminance, resolution, and efficiency to improve the device quality. Since the first OLED microdisplays were developed in the late 1990s [8,9], OLED microdisplay technology has been rapidly improving. After the company eMagin, which pioneered OLED microdisplays, released its SVGA+ product in the market in 2001, many companies such as MicroOled (France), Sony (Japan), OlighTek (China), Kopin (USA), Seeya (Chian), and LG Display (South Korea) emerged and researched and sold OLED microdisplays. To increase the applications and market share of OLED microdisplays, their device architectures, materials, and fabrication processes should be improved. In addition, the size of the OLED microdisplay panel must be expanded for a wide field of view (FoV) in AR/VR glasses. A stepper is generally used for high-resolution pixel patterning in microdisplays, and its one-shot size is approximately 1 inch diagonally. Therefore, a stitching process is required for over 1-inch microdisplay panels, but it is a very difficult process for achieving high image quality. Consequently, some innovative technologies are required for large and high-resolution microdisplay panels.