Theoretically, two layers are better than one for solar-cell efficiency

Solar cells have come a long way, but inexpensive, thin film solar cells are still far behind more expensive, crystalline solar cells in efficiency. Now, a team of researchers suggests that using two thin films of different materials may be the way to go to create affordable, thin film cells with about 34% efficiency.

source https://www.sciencedaily.com/releases/2020/09/200915194250.htm