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Organic Light Emitting Transistor (OLET) - Replacement for OLEDs?

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OLED Structure

OLED Structure

The OLED above is actually three LEDs side by side. This particular arraignment of red, green, and blue is the type of light source one would see in a computer or television display.

What's missing in the graphic above? The power source. This would typically be a transistor placed nearby the OLED.

An OLET is both the light and power source.

Green, Red, and Blue LEDs

Green, Red, and Blue LEDs

What Is an LED?

First what is LED? Its an acronym that stands for "Light Emitting Diode." And to know what that is you also need to know what a diode is.

Definition: In electronics, a diode is a two-terminal electronic component that conducts electric current in only one direction. Diodes made with specific materials can emit light when current flows through them. This is the nature of an LED.

An Organic LED is made with materials that are carbon based. This means that they can also be made with specific types of flexible material such as plastics.

When current is pumped through a diode the positive flow of electrons combining with the negatively charged area causes an energy release; with OLEDs this is in the form of photons or light.

LED Drawbacks
Despite their meager power requirements, light emitting diodes actually use more power than an equivalent transistor would. There are two other drawbacks as well. First, the time it takes the OLED to shine its brightest is preceded by a slight delay. Second, there is an upper limit on how much light an OLED can produce. Once that limit is reached no more photons can be "pumped" out of them.

This means that when OLEDs are used as part of a display matrix, like the display in many laptops and the flat-panel displays made these days, there will always be a slight lag between the time power is applied and that power is turned into light. The net effect is that displays using OLEDs will always be hampered by a finite response time. Something manufacturers would prefer to work around as newer more advanced displays are made for public consumption.

Also, because OLEDs can only produce so much light there is a definite number required to provide an adequately bright display. Power demand increases with an increased number of OLEDs and, if the device is battery powered, the display can be a real draw on power requirements.

An OLET is an Organic Light Emitting Transistor. This is likely going to be the replacement technology for LEDs for a number of reasons; not the least of which is reduced power requirements.



In the image above are shown a Light Emitting Diode with the required supporting power transistor.

Below that an Organic Light Emitting Transistor.

It is quite clear from the diagram that an OLET takes up half the physical space of the traditional LED.

The Advantage of Organic Light Emitting Transistors

What is an OLET?
Definition: An Organic Light Emitting Transistor (OLET) is a form of transistor that emits light.

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Because OLETs can be made much more efficient it is believed that the “Organic light-emitting transistors” could be the new optoelectronic light source; replacing OLEDs for a number of viable reasons.

Here is the crux of this idea. A transistor that can emit light and is also made of organic material (read plastic) could be considerably cheaper to manufacture than equivalent LEDs. This, in turn, could bring the price of displays down considerably.

There are additional benefits too. An OLET is much faster that an LED is projecting light. There's no lag time between when power is applied and when light is produced.

Then there's the switching circuitry. An LED needs transistors to power them; an OLET is the transistor powering the light source and it is the light source as well.

This single advantage could cut down the amount of circuitry to drive displays considerably. And reduced circuitry means reduced cost and as well as more efficient use of electricity.

Additionally an OLET could end up in places where an OLED cannot go. And because they are organic they can also be made on flexible surfaces.

To put all this another simpler way the following advantages can be seen in OLETs:

  • A transistor-based light source switches on or off much faster than an OLED
  • An OLET requires less circuitry; it is the switch and the light both
  • An OLET has better light output at less power than an OLED
  • The amount of light produced can be adjusted more than with an OLED
  • Because OLETs are layered materials they can be integrated onto computer chips; LEDs cannot
  • Because OLETs can be integrated into chips transmission speeds are reduced

Ultimately, OLETs can be made with common carbon based (this is what makes them organic) materials, in higher densities, with improved energy consumption, and even be much easier to manufacture. Best of all OLETs convert almost 100% of the energy they are fed into light. This makes them very efficient.

With the advent of OLETs we would could all see better, faster and clearer flat-panel televisions. Such displays would have higher refresh rates (crisper images), and use less power as well (currently these flat panel displays use almost twice the power of an older tube-type TV).

Current Drawback
There's just one and that is the lack of brightness. Researchers believe they can improve this with better manufacturing techniques that reduce the thickness of the material layers thus letting more light through those layers.


Though this is almost entirely in the research phase it's good to see that researchers are looking beyond the OLED and LED as the sole solid state light source for a wealth of applications.

The OLET promises improved performance, better brightness, and reduced power consumption in a world that seems bent on having every electronic device we use powered by a rechargeable battery this is a very good direction to go.

And of course if circuits are designed to sip power in portable devices they'll be that much better as house current devices as well.


The author was not compensated in any way, monetarily, with discounts, or freebies by any of the companies mentioned.

Though the author does make a small profit for the word count of this article none of that comes directly from the manufacturers mentioned. The author also stands to make a small profit from advertising attached to this article.

The author has no control over either the advertising or the contents of those ads.


LiamBean (author) from Los Angeles, Calilfornia on March 12, 2011:

Nan: Thanks, but I'm trying to present this in such a way that the non-technical can understand it. I know the jargon gets kind of thick, but I really can't avoid the terms.

Nan Mynatt from Illinois on February 23, 2011:

Great for professionals who understand your language and the physics of light transformation. I can tell that you are very knowledgeable about the subject.

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