Question: What would be an example of a plasmonic device that would convert light into electricity?

Lewis Wright answered on 6 Mar 2017:

WARNING: the following answer contains LOTS of speculation and is, at best, an educated guess. THIS IS NOT FACT! If anyone can be more accurate, please leave a comment!
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This is a really interesting question that I have done some reading on, and will do my best to answer.

Plasmons can be compared to phonons, in that they are both ‘quasiparticles’. A quasiparticle is something that cannot be divided into smaller chunks, and has other properties like a regular particle, but isn’t found in the Standard Model.

A phonon is vibration due to heat energy, and comes in specific (quantised) energies. It can be modelled and explained using some particle dynamics but isn’t an actual, physical thing like an electron.
A plasmon is a specific amount of energy found in a plasma. A plasma is what forms when lots of electrons are excited out of a large number of atoms, and all interact with each other. It can be thought of like water; if you make a splash in water, it ripples along the surface and transfers its energy. If you have a lot of electrons free from atoms, and you make one electron move closer to another one, they will repel each other (since they are both negatively charged) and transfer their energy on, pushing the second electron into a third, the third into a fourth, and so on. A plasmon is the energy that moves through various electrons from the initial disturbance, but it makes it easier to think about and calculate if you consider the energy itself as a single ‘particle’ (hence why it is called a quasiparticle, to distinguish the difference).

In regular solar cells (SCs), an electric field is established by bringing two types of semiconductor together; this electric field is what separates electrons from their home-atom when they are excited, and is what lets us extract useful energy from them.
A plasmonic SC uses a metal layer either side of a semiconductor. Metals have a ‘sea of electrons’ within them, which will spill over slightly into the semiconductor (if the semiconductor is thin enough). When light hits the semiconductor, it will excite an electron which will be free to move. As this extra electron joins the ‘sea’ that already exists, it will push an electron out somewhere else, which in a plasmonic SC is collected and used to power whatever it is attached to.

There are lots of different materials that can be used to make a regular SC, and they all work in the same way. The same can be said for a plasmonic SC – theoretically, any combination of metal and semiconductor would work, but some material combinations will work better than others.

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I repeat: THIS IS NOT FACT! I have never studied plasmons, and this is my understanding based on how my cells work, but with the principles of plasmons applied. THE CHANCES ARE I AM WRONG, OR AT THE VERY LEAST OVERSIMPLIFYING!
If anyone can add more detail or clarify anything, please comment!