CNT OLEDs

Many corporations and researchers have been investing a lot of money in the development of OLEDs.   

Researchers in Canada have demonstrated OLEDs based on carbon nanotube anodes that are as efficient as comparable indium tin oxide (ITO) devices. While this part seems to be only JUST equal, there are several advantages that the CNTs provide, such as increased material flexibility and hardiness. This could make them an attractive alternative to transparent conducting oxides for OLEDs.

Amazingly, many researchers say this method of creating OLEDs with CNTs is cheaper than using ITO.  Another current limitation of OLEDs is the transistors that the electric currents run along.  Right now, the current has to run ALONG the transistors, which means that for the OLED to be bright, and visible, the display has to be small.  Many Android smart phones are beginning to employ OLED screens.  This is the extent though.  OLEDs made with ITO are also, fragile, somewhat rigid and one sided.  By applying the appropriate chemical treatment, nanotubes could also replace the metal cathodes found in OLEDs. This would allow the devices to emit light from both sides. Not to mention that the OLEDs would be completely transparent, and as thin as 1 to 8 mm.

Another similar development in CNT OLEDs comes from The University of Southern California Viterbi School of Engineering.   USC is one of many groups around the world trying to perfect the technology in applications such as affordable "head-up" car windshield displays; eyeglasses to watch videos for when you are sitting in an airport or train station and ultra thin, low-power "e-paper" capable of full color motion video.

Chongwu Zhou of USCs Ming Hsieh Department of Electrical Engineering has been working on transparent electronics for the past three years and last year developed a prototype devices in which transparent electronics were built on top of a flexible transparent base.   This was accdomplished using carbon nanotubes.  Earlier attempts at transparent devices used other semiconductor materials with disappointing electronic results, enabling one kind of transistor (n-type); but not p-types; both types are needed for most applications.

The critical improvement in performance, according to the research, came from the ability to produce extremely dense, highly patterned lattices of nanotubes, rather than random tangles and clumps of the material. These new aligned nanotube transistors are easy to fabricate and integrate, as compared to individual nanotube devices. The transfer printing process allows the devices to be fabricated through low temperature processes, which is important for realizing transparent electronics on flexible substrates.

Zhou believes that we may be 2 to 6 years away from mass production of transparent electronics. One barrier is the inertia of old existing technology.

NOTE:  Samsung has released the first nanotube based OLED screen called "BluePhase".

Presentation 10/19/10: Nanotube Composite: OPVs

Currently, photovoltaics are a new trend in the production of cheap, clean, and green energy.  There are multiple ways of producing a photovoltaic, however, one thing remains a hindrance that limits the desire for photovoltaics.  Efficiency.  A standard photovoltaic cell currently operates at an efficiency of 1-3%.  Remarkably, this is not a small amount of energy.  Unfortunately, to produce enough energy using only photovoltaics, the ratio of size to received energy is not feasible.  Very large arrays of photovoltaics are needed to produce large quantities of energy.  Therefore, intense research is being conducted to increase the efficiency of photovoltaics. 

One of the key developments is a nanotube suspension (Buckypaper) in a polymer to produce a photovoltaic at up to 15 times more efficient, and potentially up to 50 times more efficient.

Initial addition of carbon nanotubes to photovoltaics give them a new name: Organic photovoltaic devices (OPVs).  They are fabricated from thin films of organic semiconductors, such as polymers and small-molecule compounds, and are typically around 100 nm thick. Because polymer based OPVs can be made using a coating process such as spin coating or inkjet printing, they are an attractive option for inexpensively covering large areas as well as flexible plastic surfaces. A promising low cost alternative to silicon solar cells, there is a large amount of research being dedicated throughout industry and academia towards developing OPVs and increasing their power conversion efficiency.
In Short, indium tin oxide (ITO) is the primary suspended conductor in a photovoltaic.  This is the substance that conducts the solar rays into energy for use.  The problem with this material is that it is brittle and not very efficient.  It is until now the most efficient material used.  Nanotubes, though increadibly strong, allow the material to become flexible and very thin.  Of course, the efficiency is over times time more than what is currently used. 

Also, Due to the simple fabrication process, low production cost, and high efficiency, there is significant interest in dye-sensitized solar cells (DSSCs). Currently, using ITO technology, dyed cells can convert energy at a rate of 11%.  Using nanotubes, this coversion rate can be increased up to 50%.  This is even newer technology and is still under development. 

Presentation 10/5/10: Buckypaper Composites