The "Thin Film Silicon Solar Cells on glass" group focuses on the development of high efficiency hydrogenated amorphous (a-Si:H) and microcrystalline (µc-Si:H) silicon single-junctions and multi-junctions solar cells in the superstrate configuration (p-i-n). The first µc-Si:H solar cells were pioneered at the PV-Lab in 1994. Microcrystalline silicon is of particular interest when combined with amorphous silicon in a solar cell tandem configuration, commonly called "micromorph", as the different optical band gaps of these materials allow for the active conversion of a larger part of the solar spectrum. In such combination, a top a-Si:H cell absorbs light with wavelengths up to 800 nm while the µc-Si:H bottom cell can absorb light in the near infrared region, allowing for larger attainable conversion efficiencies. This "micromorph" serially connected tandem cell was first introduced at the PV-Lab in the mid 1990s, and since then, an increasing number of research institutes and companies have adopted this concept.