We believe that some things will never change. 1 plus 1 equals 2. The sun rises in the east. A photon can only create one electron in a silicon solar cell. The theoretical maximum efficiency of a solar cell is 29.1%. And then one day we wake up and realize that everything has changed and that we have to relearn everything we thought we knew.

A team of researchers from MIT and Princeton have demonstrated a way to make each photon hitting silicon give rise to two electrons instead of one, opening the door to a new type of solar cell with greater efficiency than never. I had thought possible.

This does not mean that the overall efficiency is double, but could increase the efficiency of future solar cells by up to 35%. This is almost double what many conventional solar cells are capable of today.

The research result of graduate student Markus Einzinger, chemistry professor Moungi Bawendi, professor of electrical and computer engineering Marc Baldo and eight other scientists from MIT and Princeton was recently published in the journal Nature. According to Daily ScienceThe basic concept of this new technology has been known for decades, but translating it into a fully functioning silicon solar cell took years of hard work, says Baldo.

The secret to improved efficiency is a class of materials known as excitons in which “energy packets propagate like electrons in a circuit“, According to Baldo. These packets have very different properties than electrons.”You can use them to change energy, you can cut them in half, you can combine them.

The first material absorbs a photon, forming an exciton that fishes rapidly in two excited states, each with half the energy of the original state. But the most difficult thing is to make it work with silicon, a material which is not excitonic. Never before had such a coupling been carried out.

We still need to optimize the silicon cells for this process.“, Adds Baldo. On the one hand, with the new system, these cells can be thinner than the current versions. You also have to work on stabilizing the materials to make them durable. Overall, commercial applications are probably still in a few years, according to the team.

Other approaches to improving the efficiency of solar cells tend to involve adding another type of cell, such as a perovskite layer, on top of the silicon. Baldo says that “they build one cell on top of another. Basically we are making an airframe – we are turbocharging the silicon airframe. We add more current to the silicon, instead of making two cells“.

+ Information: news.mit.edu