Manufacturing of triple-junction 4 ft2 a-Si alloy PV modules

Spectrum splitting, triple-junction a-Si alloy 4 ft² PV modules have been assembled utilizing solar cells produced in a 2 Megawatt continuous roll-to-roll manufacturing line. This manufacturing line produces solar cells on a 5 mm thick, 14 inch wide and 2500 foot long stainless steel roll at a speed of 1 ft/min. The layered structure of the solar cells is: SS/Ag/ZnO/n₁i₁p₁//n₂i₂ p₂/n₃i₃p₃/TCO, where i ₁ is band-gap graded a-SiGe alloy, i₂ and i₃ are a-Si and all of p₁, p₂ and p₃ are μc-Si p⁺. These PV modules provide 9.5% initial and 8.0% stable conversion efficiencies, the highest reported values for a-Si alloy production modules (⩾4 ft²). Major accomplishments which produced the significant efficiency included: (1) the incorporation, for the first time, of a band-gap profiled a-SiGe narrow band-gap solar cell into a continuous roll-to-roll process; (2) the incorporation, for the first time, of a high performance texturized Ag/ZnO back-reflector system into a continuous roll-to-roll process with production subcell yields greater than 99%