OLED SEMINAR REPORT PDF
“OLED TECHNOLOGY” A Seminar Report Submitted in partial fulfillment of The requirements for the award of the Degree of BACHELOR OF TECHNOLOGY IN. pdf, report, presentation, source code, abstract, seminar, project idea, seminar topics, project, project topics,latest technology,Organic LED Display-OLED idea. OLED. Seminar Report On OLED. ABSTRACT. OLED is a solid state device composed of thin OLEDs can have either two layers or three layers of organic.
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oled seminar report - Free download as Word Doc .doc /.docx), PDF File .pdf), Text File .txt) or read online for free. this report describe oled technology for. Seminar Report On OLED - Download as Word Doc .doc), PDF File .pdf), Text File .txt) or read online. Organic LED full report - Download as Word Doc .doc), PDF File .pdf), Text File ( .txt) Organic LED Seminar Report ' OLED based flat panel displays as.
Furthermore, plastic substrates are shatter-resistant, unlike the glass displays used in LCD devices. This also provides a deeper black level , since a black OLED display emits no light. Better power efficiency and thickness LCDs filter the light emitted from a backlight , allowing a small fraction of light through. Thus, they cannot show true black. However, an inactive OLED element does not produce light or consume power, allowing true blacks. Emission intensity is enhanced when the IML thickness is 1.
The refractive value and the matching of the optical IMLs property, including the device structure parameters, also enhance the emission intensity at these thicknesses. Due to their extremely fast response time, OLED displays can also be easily designed to be strobed, creating an effect similar to CRT flicker in order to avoid the sample-and-hold behavior seen on both LCDs and some OLED displays, which creates the perception of motion blur.
This is lower than the typical lifetime of LCD, LED or PDP technology; each currently is rated for about 25,—40, hours to half brightness, depending on manufacturer and model. One major challenge for OLED displays is the formation of dark spots due to the ingress of oxygen and moisture, which degrades the organic material over time whether or not the display is powered. Please help improve it to make it understandable to non-experts , without removing the technical details. April Degradation occurs because of the accumulation of nonradiative recombination centers and luminescence quenchers in the emissive zone.
In particular: Lifespan info is 11 years old.
Please update this section to reflect recent events or newly available information. Thus, the cathode gives electrons to the emissive layer and the anode withdraws electrons from the conductive layer; in other words, the anode gives electron holes to the conductive layer.
Soon, the emissive layer becomes negatively charged, while the conductive layer becomes rich in positively charged holes. Electrostatic forces bring the electrons and the holes towards each other and recombine. This happens closer to the emissive layer, because in organic semiconductors holes are more mobile than electrons unlike in inorganic semiconductors. The recombination causes a drop in the energy levels of electrons, accompanied by an emission of radiation whose frequency is in the visible region.
That is why this layer is called emissive. The device does not work when the anode is put at a negative potential with respect to the cathode. In this condition, holes move to the anode and electrons to the cathode, so they are moving away from each other and do not recombine.
Indium tin oxide is commonly used as the anode material. It is transparent to visible light and has a high work function which promotes injection of holes into the polymer layer. Metals such as aluminium and calcium are often used for the cathode as they have low work functions which promote injection of electrons into the polymer layer.
The organic light emitting diode OLED is a p-n diode, in which charge-carriers e-h pairs recombine to emit photons in an organic layer. The thickness of this layer is approximately nm experiments have shown that 70 nm is an optimal thickness. When an electron and a hole recombines, an excited state called an exciton is formed. Depending on the spin of the e-h pair, the exciton is either a singlet or a triplet.
An electron can have two different spins, spin up and spin down. When the spin of two particles is the same, they are said to be in a spin-paired, or a triplet state, and when the spin is opposite they are in a spin-paired singlet state. On the average, one singlet and three triplets are formed for every four electronhole pairs, and this is a big inefficiency in the operation of the diodes.
A singlet state decays very quickly, within a few nanoseconds, and thereby emits a photon in a process called fluorescence. A triplet state, however, is much more long-lived 1 ms - 1 s , and generally just produce heat.
One method of improving the performance is to add a phosphorescent material to one of the layers in the OLED.
This is done by adding a Organic Light Emitting Diodes www. The exciton can then transfer it's energy to a phosphorescent molecule which in turn emits a photon. It is however a problem that few phosphorescent materials are efficient emitters at room temperature. Figure 1: Two different ways of decay. There have been devices manufactured which transforms both singlet and triplet states in a host to a singlet state in the fluorescent dye.
This is done by using a phosphorescent compound which both the singlets and triplets transfer their energy to, after which the compound transfer its energy to a fluorescent material which then emits light.
Using one organic layer has some problems associated with it. The electrodes energy levels have to be matched very closely, otherwise the electron and hole currents will not be properly balanced. This leads to a waste in energy since charges can then pass the entire structure without recombining, and this lowers the efficiency of the device. With two organic layers, the situation improves dramatically.
Now the different layers can be optimized for the electrons and holes respectively. The charges are blocked at the interface of the materials, and waits there for a partner. Considerably better balance can be achieved by using two organic layers one of which is matched to the anode and transports holes with the other optimized for electron injection and transport.
Each sign of charge is blocked at the interface between the two organic layers and tend to "wait" there until a partner is found.
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Recombination therefore occurs with the exciton forming in the organic material with the lower energy gap. The fact that it forms near the interface is also beneficial in preventing quenching of the luminescence that can occur when the exciton is near one of the electrodes. Another improvement is to introduce a third material specifically chosen for its luminescent efficiency. Now the three organic materials can be separately optimized for electron transport, for hole transport and for luminescence.
Holes and electrons are injected from opposite contacts into the organic layer sequence and transported to the emitter layer.
Recombination leads to the formation of singlet excitons that decay radiatively. In more detail, electroluminescence of organic thin film devices can be divided into five processes that are important for device operation: a Injection: Electrons are injected from a low work function metal con-tact, e. Ca or Mg. The latter is usually chosen for reasons of stability. A wide-gap transparent indium-tin-oxide ITO or polyaniline thin film is used for hole injection.
In addition, the efficiency of carrier injection can be improved by choosing organic hole and electron injection layers with a low HOMO high occupied molecular orbital or high LUMO lowest unoccupied molecular orbital level, respectively. Therefore, preferentially hole or electron transporting organic compounds with sufficient mobility have to be used to transport the charge carriers to the re-combination site.
Since carriers of opposite polarity Organic Light Emitting Diodes www. Thin electron or hole blocking layers can be inserted to improve the selective carrier transport. Recombination of filled traps and free carriers may also attribute to the formation of excited states. Energy barriers for electrons and holes to both sides of the emitter layer allow to spatially confine and improve the recombination process.
Embedding the emitter layer into transport layers with higher singlet excitation energies leads to a confinement of the singlet excitons and avoids non-radiative decay paths. Doping of the emitter layer with organic dye molecules allows to transfer energy from the host to the guest molecule in order to tune the emission wavelength or to increase the luminous efficiency.
Factors Influencing Performance Various factors influence the quality of the OLED, including the choice of materials, thickness, geometry, purity of samples, and contamination from air or other sources.
Different combinations will emit different colors and have different lifetimes. The two most important factors are electron mobility and energy levels of the highest unoccupied molecular orbital HOMO and the lowest unoccupied molecular orbital LUMO. A small energy gap enhances the conditions for electron flow. The same is true for the holes as they travel in the opposite direction. The energy gap between successive levels is on the order 0.
When they meet, they emit a quantum of light or travel as an exciton. Materials are chosen so that the energy levels match in going from one level to another.
In general, the absolute value of the energy level increases in going from the anode to the to HTL and in going from the cathode to the ETL including any layers in between. Often buffer Organic Light Emitting Diodes www. The buffers work by the same mechanism, aiding electron flow. Hole and Electron Mobility Another major factor influencing performance is hole and electron mobility.
The low electron mobility of most organic materials prevents their use as materials in an ETL layer. The success of their performance is due to the behavior of the -bonds.
They behave as semiconductors, due to the small energy gap between the highest unoccupied -orbital and the lowest unoccupied -orbital. Within the ring structures, the -orbitals overlap one another. This overlap of the adjacent -orbital wave functions makes the electrons relatively delocalized, i. In traditional OLEDs, the light emission is based on fluorescence, a transition from a singlet excited state of a material.
With the electro phosphorescent materials used as a dopant, which exploits both singlet and triplet excited states, this upper limit is virtually eliminated. OLED Fabrication OLEDs are typically fabricated on a transparent substrate on which the first electrode usually indium-tin-oxide which is both transparent and conductive is first deposited.
Then one or more organic layers are coated by either thermal evaporation in the case of small organic dye molecules, or spin coating of polymers. The total thickness of the organic layers is of order nm. Lastly, the metal cathode such as magnesium-silver alloy, lithium-aluminum or calcium is evaporated on top.
These metals are chosen for their low workfunctions in order that they provide efficient injection of electrons. The two electrodes add perhaps nm more to the total thickness of the device.
Therefore the overall thickness and weight of the structure is mostly due to the substrate itself. The OVPD production process utilizes a carrier gas stream in a hot walled reactor at very low pressure to precisely deposit the thin layers of organic materials used in OLED displays.
Conventional OLED fabrication equipment evaporates the organic molecules at high temperature and pressure. I express my heartfelt gratitude to all my teachers for his valuable suggestion and guidance, without their cooperation this report is incomplete.
I express my thanks to all my friends for his valuable suggestion and comments during my seminar preparation. No Topic Name Page No. Abstract 2 2. Introduction 3 3. History 4.
OLEDs structure 6 5. OLEDs working principle 5. Working 5.
Types of OLEDs 6. Applications of OLEDs 15 Current research on OLEDs 15 The organic future of OLEDs 16 Conclusion 17 Generation of OLED 0 4 2. Slight emitting diode 1 4 3. Multi layered OLED 2 5 4.
Structure of OLED 6 6 8. Working of OLED 7 7 9. Colour creation 8 8 Passive OLED 9 9 Active OLED 10 10 Transparent OLED 11 10 Top emitting OLED 12 11 Foldable OLED 13 12 White OLED 14 12 OLED can provide displays on electronic devices and use less power than conventional light emitting diodes i.
LED used today. Like an LED, an OLED is a solid state semiconductor device that is to nanometers thick and times smaller than the human hair.
OLED can have two layers or three layers of organic material. It emits light through a process called electrophosphorescene. The layers are made up of small organic molecules or macro polymers that conduct electricity. They have conductivity levels ranging from insulators to conductors, so OLEDs are considered as organic semiconductors. The layer of organic semiconductor material is formed between two electrodes, where at least one of the layers is transparent.
This layer of organic semiconductor material is formed between two electrodes, where at least one of the electrodes is transparent. Such devices can be used in television screens, computer monitors, small, portable system screens such as cell phones and PDAs, watches, advertising, information and indication. OLEDs can also be used in light sources for general space illumination, and large-area light-emitting elements.
Due to the younger stage of development, OLEDs typically emit less light per unit area than inorganic solid-state based LEDs which are usually designed for use as point-light sources. OLED displays do not require a backlight to function.No vacuum is required, and the emissive materials can also be applied on the substrate by a technique derived from commercial inkjet printing.
With our electro phosphorescent materials used as a dopant.
oled seminar report
A composite layer is formed on the handling substrate; a thin film transistor array is formed on the composite layer. The OVPD design should also be adaptable to the rapid.
Bulbs were used at that time. The technology has the potential to not only improve existing products. What is OLED? They also have the true-colour qualities of incandescent lighting. Vinzz Sagoo. Search inside document.
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