[ODCAD] Philips-High Effcient Polymer OLED
Improvement of power efficiency is critical for success of OLED display technology. Scientists from Philips claims that a breakthrough in that aspect has been made.
One development Philips made is using proper hole transportation layer (HTL) material. Usually, conductive polymer has more hole injected than electron, which results in waste of energy from extra hole. Choosing proper HTL material to reduce the hole injected can improve the power efficiency. (Sounds like anode junction barrier is increased) The quantum efficiency has been raised to 12% that is about 3 to 6 times higher than standard OLED devices.
Another development Philips made is dispersing a phosphorescent guest material into a light emitting polymer host. The polymer host used by Philips is carbazole-oxadiazole derivative. The guest material is iridium complex. A research fellow Meulenkamp from Philips presented the work on April 28, 2004 at the International Society for Optical Engineering's Photonics Europe conference in Strasbourg, France. Philips expects that these developments can significantly improve polymer OLED (PLED) device performance.
Copy right owned by OD Software Incorporated (ODSI)(http://www.odcad.com/)-the expert and toolkit provider of electronic material, device
Saturday, May 01, 2004
[ODCAD] Blue Color Life of OLED
The industry standard for display device life is 100,000 hrs. LCD and Plasma are two popular FPD technologies. All of them have reached this standard.
Color of OLED can be achieved by three elemental color materials. Each material gives one of the colors Red, Yellow and Blue. There are the other technologies to achieve full color of OLED, which will be covered later.
One of targets of OLED is to increase the life of each color material. This is particularly true for Blue color material. The longest life for this is 45,000 hr (this is my knowledge, you may share with us if you have the latest info). For chemist, material scientist, it is a great job ahead of them.
ODCAD from OD Software Incorporated (ODSI) (http://www.odcad.com/)-the expert, and tookit provider of electronic material and device.
The industry standard for display device life is 100,000 hrs. LCD and Plasma are two popular FPD technologies. All of them have reached this standard.
Color of OLED can be achieved by three elemental color materials. Each material gives one of the colors Red, Yellow and Blue. There are the other technologies to achieve full color of OLED, which will be covered later.
One of targets of OLED is to increase the life of each color material. This is particularly true for Blue color material. The longest life for this is 45,000 hr (this is my knowledge, you may share with us if you have the latest info). For chemist, material scientist, it is a great job ahead of them.
ODCAD from OD Software Incorporated (ODSI) (http://www.odcad.com/)-the expert, and tookit provider of electronic material and device.
Tuesday, April 27, 2004
[ODCAD] Charge Carrier Mobility and Future of Organic Semiconductor
This is comment about Eugen's reply of "Organic TFT Transistor:
Interface and Performance". Regarding the future of organic device,
Eugen is right. From science aspect, there is no
reason to stop this semiconductor technology to replace Si.
In the article "Organic TFT Transistor: Interface and Performance",
ODCAD does mention that there is one issue that is low
mobility of charge carrier. This doe not mean this kind of material
Cannot reach high mobility. As mentioned in the article, it is due to
disorder of the material structure, this is particularly true for
polymer semiconductor. However, once the engineers and scientists
know how to deposit the organic semiconductor in the way that the
material is good order. The mobility will not be issue at all.
One example to prove this is material C6 nanotube. No any adult, it
is organic. The carbon in the material is very ordered due to the
sigma bond. The conjugated p orbital of the carbon form excellent
conduction channel. Its charge carrier mobility is much higher than
all metal material because the charge carrier does have much less
chance to hit the carbon (electron-phonon interaction, plus the other
effect).
Overall, organic semiconductor has great future. At the current
technology level, it is already taking over Si technology in some
areas such as TFT, LED etc.
ODCAD from OD Software Incorporated (ODSI)(http://www.odcad.com/)-the expert and tool kit provider of electronic material, device
This is comment about Eugen's reply of "Organic TFT Transistor:
Interface and Performance". Regarding the future of organic device,
Eugen is right. From science aspect, there is no
reason to stop this semiconductor technology to replace Si.
In the article "Organic TFT Transistor: Interface and Performance",
ODCAD does mention that there is one issue that is low
mobility of charge carrier. This doe not mean this kind of material
Cannot reach high mobility. As mentioned in the article, it is due to
disorder of the material structure, this is particularly true for
polymer semiconductor. However, once the engineers and scientists
know how to deposit the organic semiconductor in the way that the
material is good order. The mobility will not be issue at all.
One example to prove this is material C6 nanotube. No any adult, it
is organic. The carbon in the material is very ordered due to the
sigma bond. The conjugated p orbital of the carbon form excellent
conduction channel. Its charge carrier mobility is much higher than
all metal material because the charge carrier does have much less
chance to hit the carbon (electron-phonon interaction, plus the other
effect).
Overall, organic semiconductor has great future. At the current
technology level, it is already taking over Si technology in some
areas such as TFT, LED etc.
ODCAD from OD Software Incorporated (ODSI)(http://www.odcad.com/)-the expert and tool kit provider of electronic material, device
Wednesday, April 14, 2004
[ODCAD] Mobility Effect :Junction of Organic Semiconductor, Electrode
The charge carrier mobility is critical information for the simulation (modeling) of electronic devices such as OLED, TFT etc. Its value of organic semiconductor is usually much lower than crystal Si material. This low mobility has impact to the transistor (see "Organic TFT Transistor: Interface and Performance"). Also, it has impact to the electrical behavior of the other device.
For a layered structure device, say a simple three layer DIODE device: bottom electrode, middle semiconductor, top electrode. Assume the bottom junction is ohmic, then the diode is due to the top junction. One popular approximate equation is Schottky junction model. The reversed current J0 measured for the junction is usually 6 order (or higher) less than what the model predicts (see "Reversed Current in Schottky Junction"). What is the reason to cause this?
There are quite few reasons for this. One important effect is due to the slow mobility of the charge carrier. A complete model considering charge injection and charge diffusion is Thermionic Emission-Diffusion model (Sze 2nd Edition). In this model, the mobility effect (drift velocity) is trivial if it is large enough compared with thermal charge carrier velocity. Otherwise, the injected current is proportion to the drift velocity that is the product of mobility and field. Dr. Scott from IBM lab in San Jose, CA) has done a set of experiments and the results have confirmed the mobility effect.
This does tell us that the current can be dependent on the mobility even it is at junction control. For device engineer, he (she) has to design (choose) the material to ensure the current obtained from the device can meet the requirements.
More related articles can be found in Electronic Devicess Group (click the link to join the group).
Copy right owned by OD Software Incorporated (ODSI)-the expert and tool kit provider of electronic material, device.
The charge carrier mobility is critical information for the simulation (modeling) of electronic devices such as OLED, TFT etc. Its value of organic semiconductor is usually much lower than crystal Si material. This low mobility has impact to the transistor (see "Organic TFT Transistor: Interface and Performance"). Also, it has impact to the electrical behavior of the other device.
For a layered structure device, say a simple three layer DIODE device: bottom electrode, middle semiconductor, top electrode. Assume the bottom junction is ohmic, then the diode is due to the top junction. One popular approximate equation is Schottky junction model. The reversed current J0 measured for the junction is usually 6 order (or higher) less than what the model predicts (see "Reversed Current in Schottky Junction"). What is the reason to cause this?
There are quite few reasons for this. One important effect is due to the slow mobility of the charge carrier. A complete model considering charge injection and charge diffusion is Thermionic Emission-Diffusion model (Sze 2nd Edition). In this model, the mobility effect (drift velocity) is trivial if it is large enough compared with thermal charge carrier velocity. Otherwise, the injected current is proportion to the drift velocity that is the product of mobility and field. Dr. Scott from IBM lab in San Jose, CA) has done a set of experiments and the results have confirmed the mobility effect.
This does tell us that the current can be dependent on the mobility even it is at junction control. For device engineer, he (she) has to design (choose) the material to ensure the current obtained from the device can meet the requirements.
More related articles can be found in Electronic Devicess Group (click the link to join the group).
Copy right owned by OD Software Incorporated (ODSI)-the expert and tool kit provider of electronic material, device.
Thursday, April 08, 2004
[ODCAD] Organic TFT Transistor: Interface and Performance
The transistor based on organic semiconductor may not be able to replace Si technology in fast response device product such as CPU. However, for many other applications such as in address cell circuit for display device such as OLED (PLED, LED), its performance is good enough.
The current from drain Id and transconductance gm are proportion to the charge carrier mobility. Both Id and gm are two important characters to show the performance of the device. Large Id means low resistance of the device, which result in small size of the device. Large gm means high amplifying capability that also result in the reduction of device size.
For organic semiconductor, its mobility is usually much smaller than crystal Si material. The best value obtained so far is 5 cm2/V-S (some lab claims that 10 cm2/V-s). This organic material is at crystal phase. For polymer semiconductor, the mobility is even lower. The best charge carrier mobility in polymer is 0.05 cm2/V-s.
The main reason for the low mobility of the organic semiconductor is due to lack of ordered material structure like Si crystal. For TFT transistor, the important area to decide the device performance is the interface between the dielectric and the organic semiconductor. It is about 10 A thickness of the interface whose charge carrier mobility is critical.
This gives a good task for engineers. They should design the method to manufacture the device in the way that can ensure highly ordered organic semiconductor at the junction (interface). For polymer semiconductor, the direction of the order (the conjugated bond direction) should be along the charge carrier transportation direction.
Copy right owned by OD Software Incorporated (ODSI)- the expert, and tool kit provider of electronic material, devices
The transistor based on organic semiconductor may not be able to replace Si technology in fast response device product such as CPU. However, for many other applications such as in address cell circuit for display device such as OLED (PLED, LED), its performance is good enough.
The current from drain Id and transconductance gm are proportion to the charge carrier mobility. Both Id and gm are two important characters to show the performance of the device. Large Id means low resistance of the device, which result in small size of the device. Large gm means high amplifying capability that also result in the reduction of device size.
For organic semiconductor, its mobility is usually much smaller than crystal Si material. The best value obtained so far is 5 cm2/V-S (some lab claims that 10 cm2/V-s). This organic material is at crystal phase. For polymer semiconductor, the mobility is even lower. The best charge carrier mobility in polymer is 0.05 cm2/V-s.
The main reason for the low mobility of the organic semiconductor is due to lack of ordered material structure like Si crystal. For TFT transistor, the important area to decide the device performance is the interface between the dielectric and the organic semiconductor. It is about 10 A thickness of the interface whose charge carrier mobility is critical.
This gives a good task for engineers. They should design the method to manufacture the device in the way that can ensure highly ordered organic semiconductor at the junction (interface). For polymer semiconductor, the direction of the order (the conjugated bond direction) should be along the charge carrier transportation direction.
Copy right owned by OD Software Incorporated (ODSI)- the expert, and tool kit provider of electronic material, devices
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