Scientists at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory have reported a new design of perovskite solar cells that achieve an average steady-state efficiency of 18.4% and a peak efficiency of 26%.

Perovskite solar cells are made of a mix of organic molecules and inorganic elements that together capture light and convert it into electricity, similarly to silicon solar cells. However, perovskite photovoltaic devices can be made more easily and cheaply than silicon and can be on a flexible, rather than rigid, substrate.

The efficiency of the new cells is higher than any other perovskite cell and much better than the 10-20% efficiency of the polycrystalline silicon solar cells now used to power most electronic devices and homes.

This efficiency has been achieved by combining two perovskite solar cell materials – each tuned to absorb a different wavelength of sunlight – into one “graded bandgap” solar cell that absorbs nearly the entire spectrum of visible light. The two materials are separated by a single-atom thick layer of hexagonal boron nitride.

The researchers believe that these cells have great potential to be the cheapest photovoltaic cells on the market.