New developments in amorphous thin-film silicon solar cells

Thin-film silicon solar cells usually contain amorphous silicon layers made by plasma enhanced chemical vapor deposition (PECVD). This CVD method has the advantage that large-area devices can be manufactured at a low processing temperature, thus facilitating low-cost solar cells on glass, metal foil, or polymer foil. In order to obtain higher conversion efficiencies while keeping the manufacturing cost low, a new development is to introduce low bandgap materials in a multijunction device structure. A frequently used low bandgap material is amorphous silicon-germanium. Record initial efficiencies in excess of 15% have been reported for triple-junction solar cells comprising these alloys. In this paper, we present a novel manufacturing method for amorphous silicon based tandem cells suitable for roll-to-roll production.