OMEGA
Organic Multiple Exciton Generation
Exceeding the efficiency limits of silicon solar cells seems unlikely. Literally billions of dollars have been spent optimising existing cells. So how can Organic Multi Exciton Generation - OMEGA - solve the challenge?
OMEGA allows us to make more efficient use of the energy in the light from the sun. When light hits a material, it generates an excitation, which solar cells harvest to produce energy. However different colours of light have different energies. Ultra-violet light causes skin burn because it’s the highest in energy. Blue light is more energic than red light and so on. It turns out that silicon solar cells can only harvest one colour of light efficiently. All other colours either aren’t absorbed or cause the solar cell to heat up and increase degradation. OMEGA intercepts this broad spectrum of colours from the sun and converts it into a more useful form.
A bit more technical…
We exploit a process known as Singlet Fission. Singlet Fission is the generation of two excitons (the excitations mentioned earlier) from the single exciton produced when a photon hits the OMEGA material. For photons that have more than twice the energy of the silcon band gap (the energy which photons must have before they can be absorbed by silicon) this allows us to increase the efficiency by a factor of two. When we look at the broad distribution of energies that solar photons have, we can increase the absolute efficiency limit of a silicon cell from 34% to 45%.