Amorphous and micromorph Si solar cells: current status and outlook

An overview of the current status and prospects of thin-film Si photovoltaics, including both hydrogenated amorphous and microcrystalline Si as well their combination known as micromorph solar cells, with a major focus on the technological development is given. Although thin-film Si solar cells have been one of the first commercially successful photovoltaic devices, today they face a tremendous challenge from variety of bulk Si technologies (mono- and multicrystalline Si) and compound-semiconductor thin-film solar cells, both of which have managed to substantially reduce the production cost and improve power conversion efficiency. Thin-film Si photovoltaics benefiting from the mighty mainstream Si industry have demonstrated the ability to reduce the production cost and cost per peak power; however, the performance improvement of amorphous-Si panels has been only marginal and further progress is hard to expect. The power conversion efficiencies of micromorph solar cells have already exceeded those of amorphous-Si devices. However, to improve their market penetration and even to hold their current share, the micromorph Si solar modules need to improve their performance, which today is approaching 11%, along the path to potential 15%, while keeping the manufacturing cost low. Further progress will require the improvement of light-trapping technologies and contact performance.