Perovskite solar cell

A family of crystal materials that absorb sunlight strongly and can be laid down as thin films, often stacked on silicon cells.

• A layer under a micrometre thick absorbs about as much light as over 100 micrometres of silicon, and can be deposited from solution at low temperature.
• Its bandgap can be tuned, so on silicon it takes the blue light and silicon the red; these tandems passed 34% in the lab, beyond silicon's ~29% limit.
• Single-layer lab cells rose from about 4% efficiency in 2009 to over 26%, faster progress than any other solar material.
• Moisture, heat and light degrade it, and most formulas contain lead; commercial panels must prove 25 years or more outdoors.