CleanEnergyWIKI - User contributions [en]

What is a Light Emitting Diode?

2009-06-24T21:29:09Z

128.95.39.55:

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==p-type and n-type Materials==
Inorganic Light emitting diodes have become very common in the last decade, used in everything from traffic lights to taillights. Inside these devices there is a very small inorganic multi-layer diode material that is driven in forward bias. Light is emitted isotropically, and a cone is used to focus the light in a single direction. In the last decade, inexpensive green and blue LEDs have become readily available in addition to the more common red.

Simplified structure of a diode:
*A piece of ''p''-type semiconductor material is created from silicon with excess dopants such as boron.
*An ''n''-type semiconductor is created from silicon doped with phosphorous.
*Joining the two pieces forms a ''p-n'' diode, and creates the the potential for charge transfer between the two materials.
*The ''n'' part of interfacial area of electrons is depleted
*The ''p'' part of the interface of holes is depleted.
*This creates a built-in potential, Vbi.

==Properties of Diodes==
Diodes provide rectification. Current only flows in one direction. When voltage is applied and current passes through a resistor you get a linear plot known as Ohms law. When current passes through a diode you get an asymmetry in the voltage current response. Increasing the positive bias causes an exponential increase in the current. Conversely, with a reverse bias, the current flow decreases. A good diode should have very low turn-on voltage (Vd) with exponential increase, and very low current with negative bias.

The Shockley equation describes the current through the diode at any bias. ([http://en.wikipedia.org/wiki/Diode#Shockley_diode_equation See Wikipedia article]). Applying voltage results in current flowing across the depletion layer region.

<swf width="600" height="500">http://depts.washington.edu/cmditr/media/pndiode.swf</swf>

This is an energy level diagram as a function of distance across a PN diode. The system is at equilibrium therefore the Fermi level in both the N region and the P region are exactly the same. This is the definition of equilibrium in the condensed phase. We can think of the Fermi level as the average level of an electron entering or leaving the solid. There is significant energy difference as we move from the N region to the P region for both electrons and holes because the depletion of the majority carriers that have occurred in that system.

In the case of reverse bias we make that depletion even more significant. We increase the built-in voltage by Vd . The deplete region thickness increases. As long as it is a purified material we see very little current flowing.

In reverse bias the Fermi levels are no longer aligned because the system is not in equilibrium. There is an energy barrier that makes it very difficult for electrons in the N region to transit to the P region and similarly it is difficult for the holes to move from the P region to the N region. This is exactly the region in a organic photovoltaic cell where the application of light causes absorbs energy and causes the charge to move. However in LEDs or OLEDs you do not want current flow when there is reverse bias.

==Forward Bias in a LED==
In the forward biased diode the current flows and the depletion region is narrowed or eliminated. Majority carriers move from one region to the other. The energy bands are not in equilibrium and the energy level of the P region is lower than the N region. Electrons move from the N region to the P region and holes move from P region to N region. Forward bias in an LED moves the electron and holes. Recombination events occur at the junction and excess free energy is dissipated as light coming out of the center region. The color of light from an inorganic diode is controlled by the band gap energy for those semiconductors. The first LED were gallium arsenside that has a low bandgap that gives the red light of early calculators. As people began to tailor the bandgap of 3-5 semiconductors they have achieved orange, green and most recently blue color emission.

<swf width="600" height="500">http://depts.washington.edu/cmditr/media/led.swf</swf>
[[category:organic LED]]

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Metal Complex Dopants

2009-06-24T19:50:38Z

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==Decreasing triplet lifetime==
[[Image:oled10_tripletlife.JPG|thumb|400px]]
One of the key advances to the modern OLED was rediscovering heavy metal complexes that had very high phosphorescent quantum yields and short lifetimes. This class of compound has an iridium at the center with both an iridium nitrogen and an iridium carbon bond. It had the characteristics of an ortho-metalated Iridium Carbon bond. It readily forms a bridged dimer. The ppy ligand is a strong sigma donor and pi acceptor. The metal to ligand charge transfer excited state is a triplit with a lifetime of about 1 microsecond.

This led to other orthometalated compounds such as iridium tris ppy sytem first discovered in the 1980s. It has 3 complexing groups around the center. The emission spectrum shows a nice big stokes shift from its absorption band and narrow emission in the green which is where we want some of these OLED to operate.

==Ortho-Metallated Ir Complexes==

These represent a new class of phosphor. They are related to these tris bby complexes that are known for a number of metals, where you have interactions with two nitrogens and the two bipyramidines. The metal carbon bond turns out to be important and has impact on the redox properties. The Ir(ppy)3 form is much easier to oxidize than the Ru(bby)3 system.
The PtOEP was one of the first triplet scavengers that were used in OLEDs. This can be compared with the fac-IR(ppy)3. PtOEP has an emission wavelength farther in to the red which is not a bad thing. Both have a high quantum efficiency for phosphorescence. The PtOEP has a much longer lifetime. The external quantum yields are 1-2% for PtOEP while fac-IR(ppy)3 has an efficiency of 8%. This was exciting.

This is most efficient at this time shows external efficiency is 13% at 1000 candelas which is quite bright. It is a green emitter. These are the relevant quantum efficiency versus current density for this compound above compared to PtOEP below. These were impressive numbers. The quantum efficiency was pretty constant from 1 mA to 100 mA the. This important if you are going run devices at a variable intensity. Eventually you get a drop off at high current densities, you are probably never going to drive displays at these current densities.

Other phosphorescent dopants include iridium compounds with both ir –N and ir-C bonds. As you change the constituents of the other complex agents you go from all the way from red to green to blue. The line widths could be narrower to get purer colors.

See Sprouse 1984 <ref>Sprouse et al. J. Am. Chem. Soc. 1984, 106, 6674-6653</ref>

==Future Directions for OLEDs: Color Purity==
[[Image:Ciecolorpurity.jpg|thumb|400px|Broad emission limits color purity. Graph shows the colors possible by mixing CIE x and y coordinates]]

The idea of color purity is important. The CIE color chart shows the coordinates that you must hit if you want to get pure red, pure blue or pure green. If you want to combine them you must be in the central region. This is based on the eye’s sensitivity to these colors. If you are in the display business this is something you look at a lot. The PtOEP is a good red. The green could be better and the blue not a pure blue. Subsequent to this other compounds have been developed that hit the CIE color coordinates nicely.

Lanthanides give extremely narrow line shapes for both emission and absorption. Unfortunately these are not very efficient compared to the heavy metal complexes. The color purity is attributed to their f-f transitions.

The efficiency of blue emitters lags behind red and green due to the lack of suitable hosts. Blue emission is harder to get because it requires radical anions and radical cations which are the most positive and the most negative in terms of electrochemical potentials, and the highest excess free energy in the recombination reaction that leads to the excited state. That means you are generating the least stable radical species, the ones that are most likely to react with oxygen and water, etc. There aren’t as many compounds that emit well into the blue. These are silicon based compounds with photo luminescent emission spectrum well into the ultraviolet, that could be used as host materials for phosphorescent blue dopants. These are still being developed.

We can build very thin light sources. There are lots of things that limit efficiency which include the interface between the transparent conductor and the hole transport layer and the cathode interface with the electron transport layer. As these devices have improved in their efficiency we are seeing multilayer devices with 4 or 5 heterojunctions each with their own dopants so you can get full red, green and blue emission.

Here is summary of the kidns of molecules that have used to span the spectrum, just a small sampling.
*Aluminum quinolate was one of OLED compounds was a green emitter.
*Eu(TTA)3 is a red emitter
*Platinum ocoethyl porphyrin PtOEH was a red phosphorescent dopant
*DCM2 was a laser dye used by the Kodak group to shift the emission into the red region
*Coumarin -6 is a dopant to create green.
*Alq2 OPH was used changes slightly to get blues.

White light for room lighting is an important application.

This is a picture of Neal Armstrong at the OLED fabrication line at the Fraunhofer Institute in Dresden. A glass substrate is loaded at the back and the conductive layer is put down. Each vacuum stage allows you to put down a different layer. The next version was going to be about three times this size. Typically you load the sublimation sources with something in range of 5-50 grams so some organic chemists have had to labor long and hard to manufacture that much.
[[Image:OLED_Fabrication_Line.jpg|thumb|300px|Neal Armstrong at Fraunhofer Institute Fabrication Line]]
[[category:organic LED]]

 

== References ==

<references/>

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Light Emitting Electrochemical Processes

2009-06-24T19:47:20Z

128.95.39.55:

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This article serves as an introduction to the design and chemistry of organic light emitting diodes (OLEDs).

== Light Emission from Recombination==
Light emission in the OLED arises from recombination (electron transfer) reactions of the cation and anion radical of conjugated aromatic molecules.
Several decades ago it was noted that poly(acenes) and related poly-aromatic hydrocarbons, in very dry nonaqueous (non-polar) solvents can be reduced by one electron (chemically or electrochemically) to produce an energetic radical anion state (D-.). These same molecules can often be oxidized by one electron to produce a cation radical state (A+.).
Should A+. and D-. encounter each other in solution, a “recombination” electron transfer reaction occurs. The excess free energy in this reaction can be deposited in one of the molecular species to form its lowest excited state (singlet), or in some cases, its lowest triplet excited state. These states are the same as those created by photoexcitation of the molecule. Emission from this state occurs with a lifetime of nanoseconds, with [[Definition: Quantum Yield|quantum yields]] approaching 100% in some cases.
These “electrogenerated chemiluminescence” (ECL) processes are direct analogues of the charge recombination processes which occur in the condensed phase in an OLED. They are also closely related to the chemiluminescence and bioluminescence processes which occur in living organisms such as fireflies.

It was quickly realized that in order to create the emissive state by injection charge the following processes took place:
<embed_document width=40% height=300 >http://depts.washington.edu/cmditr/images/OLEDredox.pdf</embed_document>

[[Image:Ecl-redox.gif‎|400px|The complete sequence.]]
 

We can write this from the point of view of a homogenous electrochemical process. At the same time this was being done in the condensed phase people were beginning to explore this process in solution. Rudy Marcus used this as a central tenant in his development of electron transfer theory between small molecule systems.

== The Jablonski Diagram==
The [[Jablonksi]] diagram is a simple way to describe what is happening with small molecules and small conjugated aromatic systems. It describes the energy (wavelength) of absorbance and luminescence for aromatic molecules.
<gallery heights=200px widths=300px perrow =3>
Image:Oled1 8 jablonski.png|First, a photon is absorbed. Excited singlets are created with different vibronic excited levels. These are the vibronic levels associated with the population of the the ν=1, ν=2 levels.
Image:Oled1 10 absorbance.png|This shows the absorption spectra with its associated fine structure. This is the lowest energy of the absorption bands.
Image:Oled1_9_relaxation.png|That is followed by very fast non-radiative relaxation.
Image:Oled1_13_fluoresence.png|Finally there is fluorescence decay which gives back the energy in the form of an emissive state. The lifetime for fluorescence is on the order of nanoseconds.
Image:Oled1_14_abs-lum-graph.png|The spectral response for this molecule looks like a mirror image of the absorption spectrum. There is a small shift called the Stokes shift which is typical for planar aromatic compounds such as anthracene.
Image:Oled1_15_phosphor.png| This diagram shows both the vibronic excited state and the ground state. Once the excited singlet state has been formed there is the possibility of intersystem crossing to a triplet state. This change in spin is a forbidden process (an energy transition not normally allowed by quantum mechanics), causing triplet states to be much longer-lived.
</gallery>
Most molecules have lifetimes of 1-100 microseconds. Compounds that are most useful for OLEDs have lifetimes closer to 1 microsecond. Most people are familiar with molecules that phosphoresce with much longer lifetimes and have emission events at much longer wavelengths, making them less useful for displays.

==Color of Absorption and Emission ==
The color of absorption and emission in simple molecular systems is controlled by the structure of the molecule and by the degree of conjugation in the aromatic system.
As the number of aromatic rings increases in these molecular systems, the energy for both the absorption and emission events goes down, shifting them to the red side of the spectrum. The same can be said for the carotenoid-like assemblies where increasing the number of double bonds in the system changes both the energy of absorption and emission.
For most polyacine-like systems, there is an absorption and emission event, a small Stokes shift, and a change of wavelength of these two depending on the degree of conjugation in the aromatic system.

== The Ratio of Singlet State to Triplet ==
The ratio of singlet state to triplet state formations helps determine OLED efficiency.
[[Image:Oled1_18_spinstatics.png|thumb|left|400px|right|Singlet recombination]]
[[Image:Oled1_19_spinstatics.png|thumb|right|400px|right|Triplet recombination]]
 
<gallery widths=400 heights=300>

Image:Oled1_15_phosphor.png|Phosphorescence with linked systems
Image:Oled1_19_jablonski ratio.png|During electrochemical excitation of these systems, 25% of the energy is deposited as singlet states, and 75% of the energy is deposited as triplet states. This significantly impacts the optimization of OLEDs which use either fluorescent molecules or phosphorescent dopants to create light. The use of phosphorescent dopants has increased efficiency to the near fluorescent lighting levels.
</gallery>

The following is a simplified description of the spin statistics of recombination. We start with a molecule in which an electron has been removed. The spin of the remaining electron in the two-level diagram can either be up or down. The electron in the donor molecular can either be spin-up or spin-down. During the process of electron transfer we create either an excited singlet state of the acceptor and a neutral donor, or excited singlet state of the donor and a neutral acceptor.

During the electron transfer event, a contact ion pair (or solvent-separated ion pair if in solution) is formed. It is a single entity, so by exchanging electrons, either a singlet of the donor or singlet of the acceptor is created. Typically, the molecule with the lowest emissive energy will receive the excess energy during this process. In an actual OLED, the lowest band gap molecule will be the emissive species.

There are three types of triplets which can be formed, making it 3 times more likely to form a triplet state than a singlet state. This accounts for the 3:1 triplet to singlet ratio. Consequently, when optimizing a light source, it is important to harvest as much energy as possibly from the triplet state.

 

== Electrogenerated Chemiluminescence Studies==
Small molecules are used in electrogenerated chemiluminescence (ECL) studies to help elucidate these light emitting processes in condensed phases.
[[Image:Oled1 23 threeECLmolecules.png|center|400px]]
Several other molecular species are now known to provide stable one-electron reduced states and one-electron oxidized states in dry, non-polar solvents. These recombination charge transfer processes produce blue-emitting states (diphenylanthracene, [[DPA]]), green-emitting states (di-isoamylquinacridone, DIQA, and other N,N’ dialkyl derivatives of quinacridone), yellow-emitting states (rubrene), and red-emitting states (ruthenium-trisbypryidine, Ru(bpy)+3). The emissive states of these molecules can be produced by charge transfer reactions between their reduced and oxidized forms. The separation in formal potentials for oxidation by one electron and reduction by one electron, expressed in electron volts, slightly exceeds the energy needed to directly excite the molecule to its lowest singlet state (S0 → S1).
[[category:organic LED]]

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Light Emitting Electrochemical Processes

2009-06-24T19:46:49Z

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This article serves as an introduction to the design and chemistry of organic light emitting diodes (OLEDs).

== Light Emission from Recombination==
Light emission in the OLED arises from recombination (electron transfer) reactions of the cation and anion radical of conjugated aromatic molecules.
Several decades ago it was noted that poly(acenes) and related poly-aromatic hydrocarbons, in very dry nonaqueous (non-polar) solvents can be reduced by one electron (chemically or electrochemically) to produce an energetic radical anion state (D-.). These same molecules can often be oxidized by one electron to produce a cation radical state (A+.).
Should A+. and D-. encounter each other in solution, a “recombination” electron transfer reaction occurs. The excess free energy in this reaction can be deposited in one of the molecular species to form its lowest excited state (singlet), or in some cases, its lowest triplet excited state. These states are the same as those created by photoexcitation of the molecule. Emission from this state occurs with a lifetime of nanoseconds, with [[Definition: Quantum Yield|quantum yields]] approaching 100% in some cases.
These “electrogenerated chemiluminescence” (ECL) processes are direct analogues of the charge recombination processes which occur in the condensed phase in an OLED. They are also closely related to the chemiluminescence and bioluminescence processes which occur in living organisms such as fireflies.

It was quickly realized that in order to create the emissive state by injection charge the following processes took place:
<embed_document width=40% height=300 >http://depts.washington.edu/cmditr/images/OLEDredox.pdf</embed_document>

[[Image:Ecl-redox.gif‎|400px|The complete sequence.]]
 

We can write this from the point of view of a homogenous electrochemical process. At the same time this was being done in the condensed phase people were beginning to explore this process in solution. Rudy Marcus used this as a central tenant in his development of electron transfer theory between small molecule systems.

== The Jablonski Diagram==
The [[Jablonksi]] diagram is a simple way to describe what is happening with small molecules and small conjugated aromatic systems. It describes the energy (wavelength) of absorbance and luminescence for aromatic molecules.
<gallery heights=200px widths=300px perrow =3>
Image:Oled1 8 jablonski.png|First, a photon is absorbed. Excited singlets are created with different vibronic excited levels. These are the vibronic levels associated with the population of the the ν=1, ν=2 levels.
Image:Oled1 10 absorbance.png|This shows the absorption spectra with its associated fine structure. This is the lowest energy of the absorption bands.
Image:Oled1_9_relaxation.png|That is followed by very fast non-radiative relaxation.
Image:Oled1_13_fluoresence.png|Finally there is fluorescence decay which gives back the energy in the form of an emissive state. The lifetime for fluorescence is on the order of nanoseconds.
Image:Oled1_14_abs-lum-graph.png|The spectral response for this molecule looks like a mirror image of the absorption spectrum. There is a small shift called the Stokes shift which is typical for planar aromatic compounds such as anthracene.
Image:Oled1_15_phosphor.png| This diagram shows both the vibronic excited state and the ground state. Once the excited singlet state has been formed there is the possibility of intersystem crossing to a triplet state. This change in spin is a forbidden process (an energy transition not normally allowed by quantum mechanics), causing triplet states to be much longer-lived.
</gallery>
Most molecules have lifetimes of 1-100 microseconds. Compounds that are most useful for OLEDs have lifetimes closer to 1 microsecond. Most people are familiar with molecules that phosphoresce with much longer lifetimes and have emission events at much longer wavelengths, making them less useful for displays.

==Color of Absorption and Emission ==
The color of absorption and emission in simple molecular systems is controlled by the structure of the molecule and by the degree of conjugation in the aromatic system.
As the number of aromatic rings increases in these molecular systems, the energy for both the absorption and emission events goes down, shifting them to the red side of the spectrum. The same can be said for the carotenoid-like assemblies where increasing the number of double bonds in the system changes both the energy of absorption and emission.
For most polyacine-like systems, there is an absorption and emission event, a small Stokes shift, and a change of wavelength of these two depending on the degree of conjugation in the aromatic system.

== The Ratio of Singlet State to Triplet ==
The ratio of singlet state to triplet state formations helps determine OLED efficiency.
[[Image:Oled1_18_spinstatics.png|thumb|left|400px|right|Singlet recombination]]
[[Image:Oled1_19_spinstatics.png|thumb|right|400px|right|Triplet recombination]]
 
<gallery widths=400 heights=300>

Image:Oled1_15_phosphor.png|Phosphorescence with linked systems
Image:Oled1_19_jablonski ratio.png|During electrochemical excitation of these systems, 25% of the energy is deposited as singlet states, and 75% of the energy is deposited as triplet states. This significantly impacts the optimization of OLEDs which use either fluorescent molecules or phosphorescent dopants to create light. The use of phosphorescent dopants has increased efficiency to the near fluorescent lighting levels.
</gallery>

The following is a simplified description of the spin statistics of recombination. We start with a molecule in which an electron has been removed. The spin of the remaining electron in the two-level diagram can either be up or down. The electron in the donor molecular can either be spin-up or spin-down. During the process of electron transfer we create either an excited singlet state of the acceptor and a neutral donor, or excited singlet state of the donor and a neutral acceptor.

During the electron transfer event, a contact ion pair (or solvent-separated ion pair if in solution) is formed. It is a single entity, so by exchanging electrons, either a singlet of the donor or singlet of the acceptor is created. Typically, the molecule with the lowest emissive energy will receive the excess energy during this process. In an actual OLED, the lowest band gap molecule will be the emissive species.

There are three types of triplets which can be formed, making it 3 times more likely to form a triplet state than a singlet state. This accounts for the 3:1 triplet to singlet ratio. Consequently, when optimizing a light source, it is important to harvest as much energy as possibly from the triplet state.

 

== Electrogenerated Chemiluminescence Studies==
Small molecules are used in electrogenerated chemiluminescence (ECL) studies to help elucidate these light emitting processes in condensed phases.
[[Image:Oled1 23 threeECLmolecules.png|center|400px]]
Several other molecular species are now known to provide stable one-electron reduced states and one-electron oxidized states in dry, non-polar solvents. These recombination charge transfer processes produce blue-emitting states (diphenylanthracene, [[DPA]]), green-emitting states (di-isoamylquinacridone, DIQA, and other N,N’ dialkyl derivatives of quinacridone), yellow-emitting states (rubrene), and red-emitting states (ruthenium-trisbypryidine, Ru(bpy)+3). The emissive states of these molecules can be produced by charge transfer reactions between their reduced and oxidized forms. The separation in formal potentials for oxidation by one electron and reduction by one electron, expressed in electron volts, slightly exceeds the energy needed to directly excite the molecule to its lowest singlet state (S0 → S1).
[[category:organic LED]]

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The OLED Test Cell

2009-06-24T19:36:48Z

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==Solution Electrogenerated Chemiluminescence Example Molecules==
[[Image:OLED2 ECL.PNG|thumb|300px]]
The following examples will focus on Diphenylanthracene since so much is known about its electrogenerated chemiluminescence ([[ECL]]). Diphenylanthracene (DPA), Di-iosamyl quinacridone, and Rubrene have the following characteristics:
*Absorbance spectra in solution with vibronic fine structure
*A small Stokes shifts
*Luminescence spectra with corresponding vibronic fine structure

 

==Prototype Emissive Devices==
[[Image:OLED2 prototype.JPG|thumb|300px]]
Interest in ECL was so strong that in the 1970s several investigators decided it might be a usable way to create light. An electrochemical cell can be built with two electrodes separated by a narrow space filled with solution in which both acceptors (A) and donors (D) are located. A and D could be two different chemicals, or the same (as with [[diphenylanthracene]]). By independently controlling the potential of the two electrodes using a potentiostat, the cation radical form of A+. is generated at the anode at a diffusion-controlled rate. At the cathode you generate the radical anion form of D-. at a diffusion controlled rate. These molecules will diffuse away from the electrode at which they are produced into the solution between the electrodes. Where they meet at the center of the device the electron transfer reaction between the donor and the acceptor occurs, causing an emissive state to occur.

*Layers must be very thin so they can be filled electrochemically in a very short period of time.
*The possibility of interaction for the two molecules must be high.
*The cation and anion radicals of the molecule must have long lifetimes, and must be carefully purified.
*One of these electrodes must allow light to leave the system, otherwise there is no display.

[[image:OLED2_energetics.JPG|thumb|400px]]
The solution ECL experiment is simple to construct. A flowing solution containing both D and A is passed in front of a Pt or Au microelectrode surrounded by a reference and counter electrode in a small solution cavity. The potential of the Au or Pt electrode is alternatively pulsed positive (to generate A+.) and negative (to generate D-.) with a typical frequency of several KHz. The products of these heterogeneous electron transfer reactions diffuse away from the electrode, where they are likely to encounter each other (on the time scale of microseconds). The resultant recombination reactions generate the emissive state of one pair of these molecules. The light from that emission event is coupled out to a multi-channel detector spectrophotometer which records the emission spectrum.

One example is this non-display application used by Neal Armstrong (University of Arizona) and Mark Wightman (University of North Carolina) to study the dynamics of electron transfer and light emission. The setup has a very small solvent-containing cavity. A window in the center is positioned opposite a photomultiplier tube or some photodetector. There are three electrodes. A 5-50 micron diameter working electrode is positioned in the center, typically a small microband or microdisc electrode. The counter and reference electrodes are poised on either side. The solution cavity is able to flow in fresh solution periodically.

 

==Characterization of the Energetics of Charge Recombination==
The potential of the working electrode is modulated with respect to the reference electrode between two extremes. At one extreme it generates the cation radical (A+.) and at the other extreme it generates the anion radical (D-.).
The potential of the these two extremes is cycled at frequencies of a kilohertz or more. By quickly flipping the potential back and forth, both species are generated in the diffusion layer volume next to the electrode surface, where they can interact and give off a photon which is counted with the detector. Wightman was able to monitor single photons and single electron transfer events with this system. Further studies of the light emitting process can be conducted using spectroscopy to compare with results from the device.

==Cross Reactions==
[[Image:OLED2_ecl_cross.JPG|thumb|400px]]
This an example of a voltamogram obtained at the microelectrode for Diphenylanthracene (DPA) in a low dielectric constant solvent. The negative scan shows the microelectrode response for a one-electron reduction of DPA to its radical anion. The positive scan shows the one-electron oxidation of DPA to its radical cation form. The difference between the midpoint potentials is called the halfway potential. This shows the energy difference of the two forms, and hints at the amount of excess free energy that will be generated by the redox reaction that follows. In this reaction there is more than 3 electron volts of excess free energy. DPA's excited state easily forms and re-emits with a peak wavelength of about 450 nm. If you calculate the energy, this corresponds to 3-3.1 eV. So the electro-chemical event generated more than enough excess free energy to create the excited singlet state of DPA.

Now compare the yield of the DPA excited states while systematically changing the redox event that occurs. First generating the DPA anion with one pulse and the DPA cation with another pulse, the ΔE1/2 is about 3.33 electron volts. This forms the excited singlet state known as the “S-route” .

Next, add a second species of Methoxybenzophonone, which reduces at a slightly less negative potential. It generates an anion radical at 3.24 electron volts. Spectroscopy shows that the DPA excited state is still formed, but slightly less efficiently. It is still an S-route process.

With Benzophonone, it has a less negative potential with an excess free energy of 3.15 volts, and is still an S-route.

<embed_document width="55%" height="400">http://depts.washington.edu/cmditr/media/OLED2_ecl_redoxpairs.pdf</embed_document>

==Marcus Theory for Electron Transfer==
<embed_document width="55%" height="400">http://depts.washington.edu/cmditr/media/OLED2_marcustheory.pdf</embed_document>

The Marcus Theory for electron transfer provides some predictability to describe both probability of light emission from an ECL cross reaction, and the probability of light emission in an OLED at the interface between two dissimilar charge transporting layers.

<math>k_{et}\quad \alpha\quad exp\bigg[\frac{-(\Delta G-\lambda)^2}{4 \lambda k_BT}\bigg]\,\!</math>

All electron transfer reactions proceed through a transition state whose energy is defined primarily by the “reorganization energy” (λT). This energy can be divided into an “internal reorganization” energy (λi -- the energy needed to reorganize the internal molecular environment in going from the initial to the final state), and the “external reorganization energy" (λo – the energy needed to reorganize the solvent or condensed phase environment surrounding the molecule in proceeding from the initial to the final state).

In general as the excess Gibbs free energy (ΔE α ΔG) in the system is increased (Points a, b, c in the slides above) so that ΔE (ΔG) is close to or exceeds λT = λi + λo in magnitude, the reaction rate accelerates exponentially. For light-emitting electrochemical processes this reaction rate enhancement leads directly to greater production of emissive states. The output of the ECL process is controlled by the difference in reduction and oxidation potentials of the two reacting components.

This provides some guidance in the design of two-layer OLEDs when trying to maximize the excess free energy in the critical charge recombination process.

First, we maximize free energy at point C. Then by changing the identity of the two pairs of the redox reaction we see less free energy at point B, and then finally point A. The excited state is generated at a lower overall rate.

The rate at which the excited state occurs is proportional to the output of photons. This gives an underlying principal for the design of OLED systems. The goal is to maximize the free energy and minimize the reorganization energies for those redox events. By maximizing the rate of electron transfer, we maximize the rate of light output.

Unfortunately the design is never that simple.

*The DPA+ + BP- is shown in point A.

*The DPA+ + MOPA- is shown in point B

*The DPA+ + DPA- system is shown in point C.

By changing which species gets reduced, the excess free energy in the redox reaction is also changed.
It is possible to create an excess free energy which exceeds the reorganization energy (point D). In this case the reaction enters the “inverted region” and the reaction rate decreases. A few examples of this phenomenon have been observed in solutions and glasses, but it has not yet been reported in OLEDs.

In the “Marcus inverted region”, the excess free energy is much larger than the reorganization energy. In this case the rate of reaction may decrease. To date this has not been discovered in OLEDs. It may have occurred but it is difficult to prove.
[[category:organic LED]]

<table id="toc" style="width: 100%">
<tr>
<td style="text-align: left; width: 33%">[[Light Emitting Electrochemical Processes|Previous Topic]]</td>
<td style="text-align: center; width: 33%">[[Main_Page#Organic_Light_Emitting_Diodes|Return to OLED Menu]]</td>
<td style="text-align: right; width: 33%">[[What is a Light Emitting Diode?|Next Topic]]</td>
</tr>
</table>

OLED Device Applications

2009-05-06T20:11:21Z

128.95.39.55:

[[Main_Page#Organic_Light_Emitting_Diodes_-_OLED|Return to OLED Menu]] |
[[Light Emitting Electrochemical Processes|Next Topic]]

Organic Light Emitting Diodes (OLEDs) are just are just beginning to appear in the commercial market. These products represent the fruition of 50 years of research, building first on the principles of silicon LEDS.

The first OLED devices include TVs, computer monitors, electronic control displays, cameras, phones, and lighting.

==Advantages of OLEDs==
*Superior viewing angle- Monitors and TV screens are visible from side angles, unlike many LCD monitors.
*Color Rendition- New dopants and dyes are being developed to give OLEDs a larger range and flexibility of color rendition.
*Brightness- OLED pixels produce light rather than block light with polarizers as an LCD display does.
*Faster Response- OLED devices typically have response time of .01 ms compared to 2 ms for LEDs.
*Energy Efficiency- The OLED is an efficient, low heat light source
*Cost- New polymers and coatings will allow LEDs to be produced by printing and spin coating techniques
*Flexibility- Polymer backing and thin coatings permit OLED to flex without breaking.
*Thin- A OLED display could be paper thin.

==Device Construction==
An OLED consists of a thin transparent electrode, two or more organic transport/ emitting layers and metal cathode. When power is applied to the electrodes light is emitted from the central layer.

Individual red, green and blue emitting OLEDs are arranged in a grid with individual power supplies for each pixel. This is called a passive display. This is being replaced with active thin film transistor display that uses a transistor to control each pixel. This is called an active matrix display.

==Commercial OLED Products==
[http://www.sonystyle.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10551&storeId=10151&langId=-1&categoryId=8198552921644539854| Sony OLED TV]

http://www.universaldisplay.com/

http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=1473&pq-locale=en_US&_requestid=204

http://www.cdtltd.co.uk/

http://www.novaled.com/

[http://www.ewh.ieee.org/soc/cpmt/presentations/cpmt0401a.pdf Osram Opto Semiconductors]
[[category:organic LED]]

OLED Device Applications

2009-05-06T20:10:51Z

128.95.39.55:

[[Main_Page#Organic_Light_Emitting_Diodes_-_OLED|Return to OLED Menu]] |
[[Light Emitting Electrochemical Processes|Next Topic]]

Organic Light Emitting Diodes (OLEDs) are just are just beginning to appear in the commercial market. These products represent the fruition of 50 years of research, building first on the principles of silicon LEDS.

The first OLED devices include TVs, computer monitors, electronic control displays, cameras, phones, and lighting.

==Advantages of OLEDs==
*Superior viewing angle- Monitors and TV screens are visible from side angles, unlike many LCD monitors.
*Color Rendition- New dopants and dyes are being developed to give OLEDs a larger range and flexibility of color rendition.
*Brightness- OLED pixels produce light rather than block light with polarizers as an LCD display does.
*Faster Response- OLED devices typically have response time of .01 ms compared to 2 ms for LEDs.
*Energy Efficiency- The OLED is an efficient, low heat light source
*Cost- New polymers and coatings will allow LEDs to be produced by printing and spin coating techniques
*Flexibility- Polymer backing and thin coatings permit OLED to flex without breaking.
*Thin- A OLED display could be paper thin.

==Device Construction==
An OLED consists of a thin transparent electrode, two or more organic transport/ emitting layers and metal cathode. When power is applied to the electrodes light is emitted from the central layer.

Individual red, green and blue emitting OLEDs are arranged in a grid with individual power supplies for each pixel. This is called a passive display. This is being replaced with active thin film transistor display that uses a transistor to control each pixel. This is called an active matrix display.

==Commercial OLED Products==
[http://www.sonystyle.com/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10551&storeId=10151&langId=-1&categoryId=8198552921644539854| Sony OLED TV]

http://www.universaldisplay.com/

http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=1473&pq-locale=en_US&_requestid=204

http://www.cdtltd.co.uk/

http://www.novaled.com/

[http://www.ewh.ieee.org/soc/cpmt/presentations/cpmt0401a.pdf Osram Opto Semiconductors]
[[category:organic LED]]

Main Page

2009-05-06T20:06:25Z

128.95.39.55:

<big>'''Center for Materials and Devices for Information Technology Research'''</big> 
This wiki is a reference collection on photonics. Most of the text has been captured from a series of lectures recorded in 2005-2008 by Center faculty Jean-Luc Bredas (Georgia Tech), Neal Armstrong (University of Arizona) and Seth Marder (Georgia Tech). You may also want to search the
[http://depts.washington.edu/cmditr/cwis/SPT--Home.php CMDITR Photonics Digital Libary] for individual learning objects.

(check out the OLED section below- the first we are building out)

GRADUATE COURSE MODULES OUTLINE

== Thrust 1: Organic Electro-Optic and All-Optical Materials and Devices ==

=== Propagation of Light (Brédas) ===

*Light Propagation in Materials
*Optical Fibers
*[[Total Internal Reflection]]
*Planar Dielectric Waveguides
*Optical Fiber Waveguides
*Dispersion and Attenuation Phenomena
*Optical Fiber Materials
*Optical Communication Systems
*Materials (Carl Bonner)

===Quantum Mechanical and Perturbation Theory of Polarizability (Brédas, Robinson, Rehr)===

===Second-order Processes, Materials & Characterization ===

*Second-order Processes (Marder)
*Structure-Property Relationships for Second-order Nonlinear Optics
*Second-order NLO Materials (Marder)
*Second-order Material Design (Jen)
*Characterization of Molecular Properties of Second-order Materials (Reid)
*Characterization of Electro-optic Materials (Norwood)
*[http://thzpolymers.pbwiki.com/ THz Polymers Wiki (Hayden)]

===Third-order Processes, Materials & Characterization ===

*Introduction to Third-order Processes and Materials (Marder)
*Two Photon Absorption (Marder)
*Advanced Concepts in Third-order Processes
*Characterization of Third-order Materials (Perry)

===Synthesis of Organic Semiconductors (Luscombe, Reid) ===

===Techniques for Fundamental Processes (Ginger) ===

===Design of n-type Semiconductors for Organic Electronic Applications ===

===Lasers (Brédas) ===

===Integrated Si Photonics (Hochberg) ===

== Thrust 2: Light Sources and Organic Electronics ==

===Center Overview ===
*Photonic Integration (Dalton)

===Basics of Light (Brédas) ===

*Propagation of Light
*Reflection and Refraction
*Total Internal Reflection
*Dispersion and Scattering of Light
*Diffraction of Light

===Luminescence and Color (Brédas)===
[[Image:Cie chromaticity diagram wavelength.png|thumb|100px|]]
*[[Luminescence Phenomena]]
*[[Electromagnetic Radiation]]
*[[Electromagnetic Spectrum]]
*[[Color]]
*[[Chromaticity]]
*[[Additive and Substractive Color Mixing]]

===Molecular Orbitals (Marder, Brédas)===
*Atomic Orbitals and Nodes
*Electronegativity and Bonding between Atoms
*Sigma and Pi Orbitals
*Electronic Coupling between Orbitals
*Donors and Acceptors

===Electronic Band Structure of Organic Materials (Brédas)===
*Introduction
*Electronic Structure of Hydrogen
*The Polyene Series, Part 1
*The Polyene Series, Part 2
*Bloch's Theorem, Part 1
*Bloch's Theorem, Part 2
*Electrical Properties
*Electronic States versus Molecular Levels

===Absorption and Emission of Light (Brédas, Marder)===
*Introduction
*Changes in Absorption Spectra
*Jablonski diagram
*Absorption, Internal Conversion, Fluorescence, Intersystem Crossing, and Phosphorescence Processes
*Spectroscopy, Extinction Coefficient, Oscillator Strength, Transition Dipole Moment
*Absorption and Emission
*Photochromism
*Interchain Interactions

===Transport Properties (Brédas)===
*Introduction
*Band Regime versus Hopping Regime
*Electronic Coupling
*Model Calculations of Electronic Coupling, Part 1
*Model Calculations of Electronic Coupling, Part 2
*Small Electronic Couplings and Marcus Theory
*Intramolecular Reorganization Energy
*Electron-Phonon Coupling

===Liquid Crystals and Displays (Marder)===
*Introduction to Liquid Crystals
*Double Refraction and Birefringence
*History of Liquid Crystals
*Director – Degrees of Order in Liquid Crystals
*Classification and Examples of Liquid Crystals, Part 1
*Classification and Examples of Liquid Crystals, Part 2
*Alignment
*Freederickz Transition and Dielectric Anisotropy
*Liquid Crystal Displays

===Organic Light Emitting Diodes===
[[Image:PNNL_Light_Lab_041.jpg|thumb|200px|Blue phosphorescent OLED developed by Pacific Northwest National Laboratory.]]
*[[OLED Device Applications]]
*[[Light Emitting Electrochemical Processes]]
*[[The OLED test cell]]
*[[What is a Light Emitting Diode?]]
*[[The first OLEDs]]
*[[Organic/Organic Heterojunctions in OLEDs]]
*[[OLED Charge Mobilities]]
*[[Organic Heterojunctions]]
*[[Fluorescent/Phosphorescent Dopants]]
*[[Metal Complex Dopants]]

===Organic Solar Cells===
[[Image:Organicphotovoltaic_testcell2_800.jpg|thumb|200px|OPV Test Cell]]
*[[Organic Solar Cells|Definition]]
*[[Energy Needs]]
*[[Solar Technologies]]
*[[Major Processes in Organic Solar Cells]]
*[[Materials used in Organic Solar Cells]]
*[[Organic Heterojunctions in Solar Cells]]
*[[Physics of Solar Cells]]
*[[Energy vs Charge Transfer at Heterojunctions]]
*[[Current OPV Research Directions]]

===Organic Photonics Applications in Information Technology ===
*Modulators for Fiber Communication

===Recent Results of “State-of-the-Art” STC Research===
== Research Equipment and Devices ==
*[[Photoelectron Spectrometer XPS and UPS]]
*[[Conducting Tip Atomic Force Microscopy]]
*[[Organic Photovoltaic Fabrication and Test Apparatus]]
*[[Two-Photon Spectroscopy]]

== Research Methods ==
*[[How to Keep a Lab Notebook]]
*[[How to Give a Research Presentation]]
*[[Writing a Scientific Paper]]
*[[Writing a Successful Proposal]]
*[[Mentoring]]

==[[External Photonics Education Links]]==

==[[Acronyms and Unit Abbreviations]]==

Main Page

2009-05-06T20:04:02Z

128.95.39.55:

<big>'''Center for Materials and Devices for Information Technology Research'''</big> 
This wiki is a reference collection on photonics. Most of the text has been captured from a series of lectures recorded in 2005-2008 by Center faculty Jean-Luc Bredas (Georgia Tech), Neal Armstrong (University of Arizona) and Seth Marder (Georgia Tech). You may also want to search the
[http://depts.washington.edu/cmditr/cwis/SPT--Home.php CMDITR Photonics Digital Libary] for individual learning objects.

(check out the OLED section below- the first we are building out)

GRADUATE COURSE MODULES OUTLINE

== Thrust 1 Organic Electro-Optic and All-Optical Materials and Devices ==

=== Propagation of Light (Brédas) ===

*Light Propagation in Materials
*Optical Fibers
*[[Total Internal Reflection]]
*Planar Dielectric Waveguides
*Optical Fiber Waveguides
*Dispersion and Attenuation Phenomena
*Optical Fiber Materials
*Optical Communication Systems
*Materials (Carl Bonner)

===Quantum Mechanical and Perturbation Theory of Polarizability (Brédas, Robinson, Rehr)===

===Second-order Processes, Materials & Characterization ===

*Second-order Processes (Marder)
*Structure-Property Relationships for Second-order Nonlinear Optics
*Second-order NLO Materials (Marder)
*Second-order Material Design (Jen)
*Characterization of Molecular Properties of Second-order Materials (Reid)
*Characterization of Electro-optic Materials (Norwood)
*[http://thzpolymers.pbwiki.com/ THz Polymers Wiki (Hayden)]

===Third-order Processes, Materials & Characterization ===

*Introduction to Third-order Processes and Materials (Marder)
*Two Photon Absorption (Marder)
*Advanced Concepts in Third-order Processes
*Characterization of Third-order Materials (Perry)

===Synthesis of Organic Semiconductors (Luscombe, Reid) ===

===Techniques for Fundamental Processes (Ginger) ===

===Design of n-type Semiconductors for Organic Electronic Applications ===

===Lasers (Brédas) ===

===Integrated Si Photonics (Hochberg) ===

== Thrust 2 Light Sources and Organic Electronics ==

===Center Overview - ===
*Photonic Integration (Dalton)

===Basics of Light (Brédas) ===

*Propagation of Light
*Reflection and Refraction
*Total Internal Reflection
*Dispersion and Scattering of Light
*Diffraction of Light

===Luminescence and Color (Brédas)===
[[Image:Cie chromaticity diagram wavelength.png|thumb|100px|]]
*[[Luminescence Phenomena]]
*[[Electromagnetic Radiation]]
*[[Electromagnetic Spectrum]]
*[[Color]]
*[[Chromaticity]]
*[[Additive and Substractive Color Mixing]]

===Molecular Orbitals – (Marder, Brédas)===
*Atomic Orbitals and Nodes
*Electronegativity and Bonding between Atoms
*Sigma and Pi Orbitals
*Electronic Coupling between Orbitals
*Donors and Acceptors

===Electronic Band Structure of Organic Materials (Brédas)===
*Introduction
*Electronic Structure of Hydrogen
*The Polyene Series, Part 1
*The Polyene Series, Part 2
*Bloch's Theorem, Part 1
*Bloch's Theorem, Part 2
*Electrical Properties
*Electronic States versus Molecular Levels

===Absorption and Emission of Light (Brédas, Marder)===
*Introduction
*Changes in Absorption Spectra
*Jablonski diagram
*Absorption, Internal Conversion, Fluorescence, Intersystem Crossing, and Phosphorescence Processes
*Spectroscopy, Extinction Coefficient, Oscillator Strength, Transition Dipole Moment
*Absorption and Emission
*Photochromism
*Interchain Interactions

===Transport Properties (Brédas)===
*Introduction
*Band Regime versus Hopping Regime
*Electronic Coupling
*Model Calculations of Electronic Coupling, Part 1
*Model Calculations of Electronic Coupling, Part 2
*Small Electronic Couplings and Marcus Theory
*Intramolecular Reorganization Energy
*Electron-Phonon Coupling

===Liquid Crystals and Displays (Marder)===
*Introduction to Liquid Crystals
*Double Refraction and Birefringence
*History of Liquid Crystals
*Director – Degrees of Order in Liquid Crystals
*Classification and Examples of Liquid Crystals, Part 1
*Classification and Examples of Liquid Crystals, Part 2
*Alignment
*Freederickz Transition and Dielectric Anisotropy
*Liquid Crystal Displays

===Organic Light Emitting Diodes===
[[Image:PNNL_Light_Lab_041.jpg|thumb|200px|Blue phosphorescent OLED developed by Pacific Northwest National Laboratory.]]
*[[OLED Device Applications]]
*[[Light Emitting Electrochemical Processes]]
*[[The OLED test cell]]
*[[What is a Light Emitting Diode?]]
*[[The first OLEDs]]
*[[Organic/Organic Heterojunctions in OLEDs]]
*[[OLED Charge Mobilities]]
*[[Organic Heterojunctions]]
*[[Fluorescent/Phosphorescent Dopants]]
*[[Metal Complex Dopants]]

===Organic Solar Cells===
[[Image:Organicphotovoltaic_testcell2_800.jpg|thumb|200px|OPV Test Cell]]
*[[Organic Solar Cells|Definition]]
*[[Energy Needs]]
*[[Solar Technologies]]
*[[Major Processes in Organic Solar Cells]]
*[[Materials used in Organic Solar Cells]]
*[[Organic Heterojunctions in Solar Cells]]
*[[Physics of Solar Cells]]
*[[Energy vs Charge Transfer at Heterojunctions]]
*[[Current OPV Research Directions]]

===Organic Photonics Applications in Information Technology ===
*Modulators for Fiber Communication

===Recent Results of “State-of-the-Art” STC Research===
== Research Equipment and Devices ==
*[[Photoelectron Spectrometer XPS and UPS]]
*[[Conducting Tip Atomic Force Microscopy]]
*[[Organic Photovoltaic Fabrication and Test Apparatus]]
*[[Two-Photon Spectroscopy]]

== Research Methods ==
*[[How to Keep a Lab Notebook]]
*[[How to Give a Research Presentation]]
*[[Writing a Scientific Paper]]
*[[Writing a Successful Proposal]]
*[[Mentoring]]

==[[External Photonics Education Links]]==
==[[Acronyms and Unit Abbreviations]]==

Main Page

2009-05-06T20:02:13Z

128.95.39.55:

<big>'''Center for Materials and Devices for Information Technology Research'''</big> 
This wiki is a reference collection on photonics. Most of the text has been captured from a series of lectures recorded in 2005-2008 by Center faculty Jean-Luc Bredas (Georgia Tech), Neal Armstrong (University of Arizona) and Seth Marder (Georgia Tech). You may also want to search the
[http://depts.washington.edu/cmditr/cwis/SPT--Home.php CMDITR Photonics Digital Libary] for individual learning objects.

(check out the OLED section below- the first we are building out)

GRADUATE COURSE MODULES OUTLINE

== Thrust 1 Organic Electro-Optic and All-Optical Materials and Devices ==

=== Propagation of Light (Bredas) ===

*Light Propagation in Materials
*Optical Fibers
*[[Total Internal Reflection]]
*Planar Dielectric Waveguides
*Optical Fiber Waveguides
*Dispersion and Attenuation Phenomena
*Optical Fiber Materials
*Optical Communication Systems
*Materials (Carl Bonner)

===Quantum Mechanical and Perturbation Theory of Polarizability (Bredas, Robinson, Rehr)===

===Second-order Processes, Materials & Characterization ===

*Second-order Processes (Marder)
*Structure-Property Relationships for Second-order Nonlinear Optics
*Second-order NLO Materials (Marder)
*Second-order Material Design (Jen)
*Characterization of Molecular Properties of Second-order Materials (Reid)
*Characterization of Electro-optic Materials (Norwood)
*[http://thzpolymers.pbwiki.com/ THz Polymers Wiki (Hayden)]

===Third-order Processes, Materials & Characterization ===

*Introduction to Third-order Processes and Materials (Marder)
*Two Photon Absorption (Marder)
*Advanced Concepts in Third-order Processes
*Characterization of Third-order Materials (Perry)

===Synthesis of Organic Semiconductors (Luscombe, Reid) ===

===Techniques for Fundamental Processes (Ginger) ===

===Design of n-type Semiconductors for Organic Electronic Applications ===

===Lasers (Bredas) ===

===Integrated Si Photonics (Hochberg) ===

== Thrust 2 Light Sources and Organic Electronics ==

===Center Overview - ===
*Photonic Integration (Dalton)

===Basics of light– (JLB) ===

*Propagation of Light
*Reflection and Refraction
*Total Internal Reflection
*Dispersion and Scattering of Light
*Diffraction of Light

===Luminescence and Color===
[[Image:Cie chromaticity diagram wavelength.png|thumb|100px|]]
*[[Luminescence Phenomena]]
*[[Electromagnetic Radiation]]
*[[Electromagnetic Spectrum]]
*[[Color]]
*[[Chromaticity]]
*[[Additive and Substractive Color Mixing]]

===Molecular Orbitals – (Marder & JLB)===
*Atomic Orbitals and Nodes
*Electronegativity and Bonding between Atoms
*Sigma and Pi Orbitals
*Electronic Coupling between Orbitals
*Donors and Acceptors

===Electronic Band Structure of Organic Materials (Brédas)===
*Introduction
*Electronic Structure of Hydrogen
*The Polyene Series, Part 1
*The Polyene Series, Part 2
*Bloch's Theorem, Part 1
*Bloch's Theorem, Part 2
*Electrical Properties
*Electronic States versus Molecular Levels

===Absorption and Emission of Light – (JLB & Marder)===
*Introduction
*Changes in Absorption Spectra
*Jablonski diagram
*Absorption, Internal Conversion, Fluorescence, Intersystem Crossing, and Phosphorescence Processes
*Spectroscopy, Extinction Coefficient, Oscillator Strength, Transition Dipole Moment
*Absorption and Emission
*Photochromism
*Interchain Interactions

===Transport Properties (Bredas)===
*Introduction
*Band Regime versus Hopping Regime
*Electronic Coupling
*Model Calculations of Electronic Coupling, Part 1
*Model Calculations of Electronic Coupling, Part 2
*Small Electronic Couplings and Marcus Theory
*Intramolecular Reorganization Energy
*Electron-Phonon Coupling

===Liquid Crystals and Displays – (Marder)===
*Introduction to Liquid Crystals
*Double Refraction and Birefringence
*History of Liquid Crystals
*Director – Degrees of Order in Liquid Crystals
*Classification and Examples of Liquid Crystals, Part 1
*Classification and Examples of Liquid Crystals, Part 2
*Alignment
*Freederickz Transition and Dielectric Anisotropy
*Liquid Crystal Displays

===Organic Light Emitting Diodes - OLED ===
[[Image:PNNL_Light_Lab_041.jpg|thumb|200px|Blue phosphorescent OLED developed by Pacific Northwest National Laboratory.]]
*[[OLED Device Applications]]
*[[Light Emitting Electrochemical Processes]]
*[[The OLED test cell]]
*[[What is a Light Emitting Diode?]]
*[[The first OLEDs]]
*[[Organic/Organic Heterojunctions in OLEDs]]
*[[OLED Charge Mobilities]]
*[[Organic Heterojunctions]]
*[[Fluorescent/Phosphorescent Dopants]]
*[[Metal Complex Dopants]]

===Organic Solar Cells===
[[Image:Organicphotovoltaic_testcell2_800.jpg|thumb|200px|OPV Test Cell]]
*[[Organic Solar Cells|Definition]]
*[[Energy Needs]]
*[[Solar Technologies]]
*[[Major Processes in Organic Solar Cells]]
*[[Materials used in Organic Solar Cells]]
*[[Organic Heterojunctions in Solar Cells]]
*[[Physics of Solar Cells]]
*[[Energy vs Charge Transfer at Heterojunctions]]
*[[Current OPV Research Directions]]

===Organic Photonics Applications in Information Technology ===
*Modulators for Fiber Communication

===Recent results of “state-of-the-art” STC research===
== Research Equipment and Devices ==
*[[Photoelectron Spectrometer XPS and UPS]]
*[[Conducting Tip Atomic Force Microscopy]]
*[[Organic Photovoltaic Fabrication and Test Apparatus]]
*[[Two-Photon Spectroscopy]]

== Research Methods ==
*[[How to Keep a Lab Notebook]]
*[[How to Give a Research Presentation]]
*[[Writing a Scientific Paper]]
*[[Writing a Successful Proposal]]
*[[Mentoring]]

==[[External Photonics Education Links]]==
==[[Acronyms and Unit Abbreviations]]==

Main Page

2009-05-06T19:58:13Z

128.95.39.55:

<big>'''Center for Materials and Devices for Information Technology Research'''</big> 
This wiki is a reference collection on photonics. Most of the text has been captured from a series of lectures recorded in 2005-2008 by Center faculty Jean-Luc Bredas (Georgia Tech), Neal Armstrong (University of Arizona) and Seth Marder (Georgia Tech). You may also want to search the
[http://depts.washington.edu/cmditr/cwis/SPT--Home.php CMDITR Photonics Digital Libary] for individual learning objects.

(check out the OLED section below- the first we are building out)

GRADUATE COURSE MODULES OUTLINE

== Thrust 1 Organic Electro-Optic and All-Optical Materials and Devices ==

=== Propagation of Light (Bredas) ===

*Light Propagation in Materials
*Optical Fibers
*[[Total Internal Reflection]]
*Planar Dielectric Waveguides
*Optical Fiber Waveguides
*Dispersion and Attenuation Phenomena
*Optical Fiber Materials
*Optical Communication Systems
*Materials (Carl Bonner)

===Quantum Mechanical and Perturbation Theory of Polarizability (Bredas, Robinson, Rehr)===

===Second-order Processes, Materials & Characterization ===

*Second-order Processes (Marder)
*Structure-Property Relationships for Second-order Nonlinear Optics
*Second-order NLO Materials (Marder)
*Second-order Material Design (Jen)
*Characterization of Molecular Properties of Second-order Materials (Reid)
*Characterization of Electro-optic Materials (Norwood)
*[http://thzpolymers.pbwiki.com/ THz Polymers Wiki (Hayden)]

===Third-order Processes, Materials & Characterization ===

*Introduction to Third-order Processes and Materials (Marder)
*Two Photon Absorption (Marder)
*Advanced Concepts in Third-order Processes
*Characterization of Third-order Materials (Perry)

===Synthesis of Organic Semiconductors (Luscombe, Reid) ===

===Techniques for Fundamental Processes (Ginger) ===

===Design of n-type Semiconductors for Organic Electronic Applications ===

===Lasers (Bredas) ===

===Integrated Si Photonics (Hochberg) ===

== Thrust 2 Light Sources and Organic Electronics ==

===Center Overview - ===
*Photonic Integration (Dalton)

===Basics of light– (JLB) ===

*Propagation of Light
*Reflection and Refraction
*Total Internal Reflection
*Dispersion and Scattering of Light
*Diffraction of Light

===Luminescence and Color===
[[Image:Cie chromaticity diagram wavelength.png|thumb|100px|]]
*[[Luminescence Phenomena]]
*[[Electromagnetic Radiation]]
*[[Electromagnetic Spectrum]]
*[[Color]]
*[[Chromaticity]]
*[[Additive and Substractive Color Mixing]]

===Molecular Orbitals – (Marder & JLB)===
*Atomic Orbitals and Nodes
*Electronegativity and Bonding between Atoms
*Sigma and Pi Orbitals
*Electronic Coupling between Orbitals
*Donors and Acceptors

===Electronic Band Structure of Organic Materials – (JLB)===
*Introduction
*Electronic Structure of Hydrogen
*The Polyene Series, Part 1
*The Polyene Series, Part 2
*Bloch's Theorem, Part 1
*Bloch's Theorem, Part 2
*Electrical Properties
*Electronic States versus Molecular Levels

===Absorption and Emission of Light – (JLB & Marder)===
*Introduction
*Changes in Absorption Spectra
*Jablonski diagram
*Absorption, Internal Conversion, Fluorescence, Intersystem Crossing, and Phosphorescence Processes
*Spectroscopy, Extinction Coefficient, Oscillator Strength, Transition Dipole Moment
*Absorption and Emission
*Photochromism
*Interchain Interactions

===Transport Properties– (JLB)===
*Introduction
*Band Regime versus Hopping Regime
*Electronic Coupling
*Model Calculations of Electronic Coupling, Part 1
*Model Calculations of Electronic Coupling, Part 2
*Small Electronic Couplings and Marcus Theory
*Intramolecular Reorganization Energy
*Electron-Phonon Coupling

===Liquid Crystals and Displays – (Marder)===
*Introduction to Liquid Crystals
*Double Refraction and Birefringence
*History of Liquid Crystals
*Director – Degrees of Order in Liquid Crystals
*Classification and Examples of Liquid Crystals, Part 1
*Classification and Examples of Liquid Crystals, Part 2
*Alignment
*Freederickz Transition and Dielectric Anisotropy
*Liquid Crystal Displays

===Organic Light Emitting Diodes - OLED ===
[[Image:PNNL_Light_Lab_041.jpg|thumb|200px|Blue phosphorescent OLED developed by Pacific Northwest National Laboratory.]]
*[[OLED Device Applications]]
*[[Light Emitting Electrochemical Processes]]
*[[The OLED test cell]]
*[[What is a Light Emitting Diode?]]
*[[The first OLEDs]]
*[[Organic/Organic Heterojunctions in OLEDs]]
*[[OLED Charge Mobilities]]
*[[Organic Heterojunctions]]
*[[Fluorescent/Phosphorescent Dopants]]
*[[Metal Complex Dopants]]

===Organic Solar Cells===
[[Image:Organicphotovoltaic_testcell2_800.jpg|thumb|200px|OPV Test Cell]]
*[[Organic Solar Cells|Definition]]
*[[Energy Needs]]
*[[Solar Technologies]]
*[[Major Processes in Organic Solar Cells]]
*[[Materials used in Organic Solar Cells]]
*[[Organic Heterojunctions in Solar Cells]]
*[[Physics of Solar Cells]]
*[[Energy vs Charge Transfer at Heterojunctions]]
*[[Current OPV Research Directions]]

===Organic Photonics Applications in Information Technology ===
*Modulators for Fiber Communication

===Recent results of “state-of-the-art” STC research===
== Research Equipment and Devices ==
*[[Photoelectron Spectrometer XPS and UPS]]
*[[Conducting Tip Atomic Force Microscopy]]
*[[Organic Photovoltaic Fabrication and Test Apparatus]]
*[[Two-Photon Spectroscopy]]

== Research Methods ==
*[[How to Keep a Lab Notebook]]
*[[How to Give a Research Presentation]]
*[[Writing a Scientific Paper]]
*[[Writing a Successful Proposal]]
*[[Mentoring]]

==[[External Photonics Education Links]]==
==[[Acronyms and Unit Abbreviations]]==