Silicon and perovskite work perfectly in tandem to produce 30%+ efficient solar cells

Two groups have independently created perovskite-on-silicon tandem solar cells that surpass 30% efficiency. The two designs use different techniques to minimise losses, but together constitute an important milestone on the road to proving the value of perovskite top layers to silicon solar cells. Moreover, several other groups have already produced cells of equal or higher efficiency.

Commercial silicon solar cells generally reach efficiencies of over 24%, and one laboratory device has generated 26.8%. The theoretical maximum for silicon is about 29.5%, so significant further gains will need to come elsewhere. An obvious target is perovskite-on-silicon tandems: silicon’s bandgap is 1.12eV – the extra energy in higher-frequency photons is wasted as heat. A perovskite top layer with a bandgap around 1.7eV could theoretically increase the efficiency to 45%, but the actual gains have been much less dramatic, with previous record efficiencies all falling short of 30%.