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Solar Cell Upgrade Using Quantum Dots?

This weeks Science tells an interesting tale of yet more promising research in solar cell technology.

It seems that researchers at the University of Texas have discovered a way to increase the current maximum solar-cell efficiency from 31% to over 60%.

The current barrier of 31% exists because much solar energy is simply lost to conventional devices because it is too energetic to be converted into usable electricity. These so-called “hot electrons” just flit away, unused, in the form of heat.

To tame these hot electrons, the scientists are looking at an intriguing bit of semicondicting material called a Quantum Dot.

A quantum dot is essentially a semiconducting nanocrystal.
It is a fascinating little object that isn’t easy to describe without scratching one’s head.
Wikipedia describes it this way:

“A quantum dot is a semiconductor  whose excitons  are confined in all three spatial dimensions”

Let’s tackle some of the key words in that description shall we?

A semiconductor conducts electricity much better than an insulator but not as well as a full-fledged conductor.

Well that wasn’t too hard was it?

Excitons are quite a bit tougher. They are quasiparticles which consist of two things taken together as a whole. One of these things is a particle like an electron. Bound to this particle is the effect it has on the local environment. An example of this is an electron and an electron hole. This hole is simply the absence of an electron where one could exist. I know this is some bizarre crap (in the best sense of that word) but do some googling about this if your intrigued.

So, whatever these excitons are, they are confined or trapped in a quantum dot in such a way that they cannot move in any dimension.

This bizarre nature of quantum dots give them unique electrical and optical properties for a host of applications including the following:

  • In electronics they have shown that they can act like single-electron transistors
  • Since they are essentially zero dimensional they have excellent optical and transport properties that could find uses in diode lasers and biological sensors.
  • These dots have been shown to be a superior tool for delivering other tools into cells for genetic manipulation like gene silencing.
  • We all know that quantum computers are coming, right? Well these little buggers could make great qubits for solid-state quantum computers one day.

In the solar cell application mentioned above, quantum dots may be able to intercept the hot electrons before they fade away and add their energy to the total output of the solar cell.

Congratulations to the team working on this potentially game-changing upgrade to solar tech.

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