Even the most efficient solar cell loses a lot of energy in the form of wasted heat. But the electron-like particles that photons emit as they enter the cells could be turned into electrical energy, solving the heat loss problem.
When photons, the particles of light, enter solar cells, they can create a quasiparticle known as an exciton. The exciton is a combination of an electron and an electron hole. What’s an electron hole? It’s basically the complete opposite of an electron, but it’s not an anti-electron. It’s not matter, it’s not antimatter, it’s not really anything at all – it’s just a place where an electron should be but isn’t.
That may not sound all that important, but it’s possible for an electron and a hole to attract each other and combine into an exciton. When that happens in solar cells, it’s responsible for the heat energy that current goes wasted. The trick to reducing the heat loss is to capture as many electrons as possible before they dissipate, because those electrons can then be diverted onto a current and used for electrical energy.
Now researchers at the University of Wyoming and Colorado State have managed to do just that. They coupled together light-absorbing lead sulfide particles with electrodes made from titanium dioxide. They found that the current produced in this system contained excitons, and they were able to collect several excitons from a single photon before the particles started to break down again into their constituent parts.
This offers a chance for solar cells to trap excitons in a similar way. As long as the cells are coupled with the appropriate electrodes, they too can capture these quasiparticles before they degrade, which means they would save most of the heat and hang onto it as useful energy. It would greatly improve the efficiency of solar cells, all without even having to do anything to the basic photon capture technology.