Thin film solar cells are less expensive to produce than silicon polycrystalline photovoltaic (PV) modules. Their flexible properties allow them to be laminated directly into walls and roofing material, creating a structure that has built-in PV without looking like a building made of solar modules. Unfortunately, thin film cells are also less efficient than their silicon counterparts.

Well, they were less efficient ... until now.

Empa, the Swiss Federal Laboratories for Materials Science and Technology, has developed a flexible PV cell with an efficiency of 20.4%, breaking the previous record for flexible thin film (18.7%) and equaling the efficiency of today's rigid and fragile silicon-based solar cells.

The thin film cells are based on CIGS (copper indium gallium selenide) semiconductors, which absorb over 99% of the incident light within the first micron of the material. This means that PV cells can theoretically be just a few microns thick ... or should I say a few microns thin? With efficient thin film PV, engineers can integrate low-cost solar power into roofing material, cars, handheld devices - pretty much anything. Coupled with flexible displays and paper batteries, highly efficient thin film solar cells could lead to a generation of handheld devices that are thin enough to fit in wallet and never need to be recharged from an AC outlet.

^{Image: Empa}