back to article Optical computing a step closer with SINGLE-MOLECULE LED

Researchers at IPCMS in Strasbourg, working with a team from the Institut Parisien de Chimie Moléculaire (CNRS/UPMC), have produced an LED that consists of a single molecule. While it's unlikely ever to serve as a display, the molecular LED is an important step forward in miniaturising components to provide optical …

COMMENTS

This topic is closed for new posts.
Gold badge
Thumb Up

100 000 --> 1 photon out.

But this is v 0.1 tech at best.

However note that the molecule is much smaller than a wavelength of light.

While very inefficient it is a start of getting some kind of I/O between some kind of molecular electronic logic and the outside world.

So thumbs up for the start of the art.

1
0
Bronze badge

electrons per photon

"One photon was emitted for every 100,000 electrons injected into the wire, and the light it emitted was in the red range."

Could this be described as "good" performance?

0
0
Silver badge

Re: electrons per photon

Did this have good performance? It certainly started something!

0
0
Anonymous Coward

SEM != STM

The researchers used a scanning tunneling microscope (STM) in their experiments, not a scanning electron microscope (SEM).

1
0
Bronze badge

Bad science

"No light was emitted when the current was reversed (which demonstrates it's behaving like an LED and not merely getting hot enough to glow)."

Actually, that only demonstrates that it's acting like a diode, and only gets hot enough to glow when current is passing. I hope they have other justification for classing it as an LED.

1
2
Anonymous Coward

Re: Bad science

Whilst you are right to point out that a diode only conducts in one direction, trying to pass a current in the opposite direction will still heat a diode, probably more so than when it's passing a current in the 'working' direction, so it's a valid test.

You did know that an LED is a diode* didn't you?

*the clue is in the name.

3
1
Def
Bronze badge

Re: Bad science

If it acts like a diode and emits light... ;)

But in answer to your question, the abstract from their paper states:

The electroluminescence of a polythiophene wire suspended between a metallic surface and the tip of a scanning tunneling microscope is reported. Under positive sample voltage, the spectral and voltage dependencies of the emitted light are consistent with the fluorescence of the wire junction mediated by localized plasmons. This emission is strongly attenuated for the opposite polarity. Both emission mechanism and polarity dependence are similar to what occurs in organic light emitting diodes (OLED) but at the level of a single molecular wire.

4
0
Bronze badge

Re: Bad science

> ".. that only demonstrates that it's acting like a diode..."

Of the Light Emitting variety, perhaps? ;-)

2
2
Bronze badge

Re: Bad science

Even worse science. Trying to pass a current having a worse heating effect? Utter bollocks. A typical LED needs only a small forward voltage and will have a leakage when reverse biased of maybe a microamp. Total energy available for heating is of the order of 3 microwatts. Forward biased and lit, the voltage drop across the junction is around half a volt and the current may be up to a few Amps for a Cree LED but for a more typical variety will be maybe 50 mA. Definitely thousands of times as much energy being dissipated.

In case there is still any doubt, I did know that an LED is a diode. What I took issue with was dismissing heating as a possible source of the light for the reason stated in the article. I sincerely hope this was not present in the scientific paper, otherwise I shall have to reclassify my 1N4004 rectifiers as LEDs as they too will emit light (albeit briefly) when plugged into the mains supply!

0
1

Re: Bad science

Actually, they didn't reverse the current; they reversed the potential (i.e. voltage).

Like any good diode, when the potential is reversed, minimal current flows (leakage current). This current is not "high enough" to generate photons.

It's the difference in current flow magnitude, when potential is applied in one direction v.s. the other direction, which characterizes diodes.

1
0

Re: Bad science @Tromos

all diodes are LEDs, all diodes are photo-diodes. Just depends on the efficiency and wavelengths. . .

0
0
Bronze badge

One potential use, once perfected

Optical computing.

Less conductors between components, more light signalling between components.

0
0
This topic is closed for new posts.

Forums