20.1%-efficient industrial-type PERC solar cells applying ICP AlOx as rear passivation layer


By Thorsten Dullweber, R&D Group Leader, Institute for Solar Energy Research Hamelin (ISFH); Christopher Kranz, R&D Group, Institute for Solar Energy Research Hamelin (ISFH); Birgit Beier, Process Engineer, Institute for Solar Energy Research Hamelin (ISFH); Boris Veith, Scientist, Institute for Solar Energy Research Hamelin (ISFH); Jan Schmidt, Head of the Photovoltaics Department, Institute for Solar Energy Research Hamelin (ISFH); Björn Roos, Solar Product Manager, Singulus Technologies AG; Oliver Hohn, R&D Department, Singulus Technologies AG; Torsten Dippell, Project Manager, Singulus Technologies AG

The passivated emitter and rear cell (PERC) is considered to be the next generation of industrial-type screen-printed silicon solar cell. However, only a few deposition methods currently exist for rear passivation layers which meet both the high-throughput and low-cost requirements of the PV industry while demonstrating high-quality surface passivation properties. This paper presents an evaluation and the optimization of a novel deposition technique for AlOx passivation layers, applying an inductively coupled plasma (ICP) plasma-enhanced chemical vapour deposition (PECVD) process. High deposition rates of up to 5nm/s, as well as excellent surface recombination velocities below 10cm/s after firing, are possible using this ICP AlOx deposition process. When applied to PERC solar cells the ICP AlOx layer is capped with a PECVD SiNy layer. Independently confirmed conversion efficiencies of up to 20.1% are achieved for large-area 15.6cm x 15.6cm PERC solar cells with screen-printed metal contacts and ICP AlOx/SiNy rear side passivation on standard boron-doped Czochralski-grown silicon wafers. The internal quantum efficiency (IQE) reveals an effective rear surface recombination velocity Srear of 110±30cm/s and an internal rear reflectance Rb of 91±1%, which demonstrates the excellent rear surface passivation of the ICP AlOx/SiNy layer stack. Currently, the ICP AlOx deposition process is being transferred from the ISFH laboratory-type tool to the Singular production tool of Singulus Technologies in order to commercialize this novel deposition process during 2012.

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The seventeenth edition of Photovoltaics International applauds new markets emerging to plug the deployment gaps left by countries such as Spain, the Czech Republic and Italy. Profitless prosperity is the way Mark Osborne, Senior News Editor at characterises the PV manufacturing supply chain at the moment. In this issue the Fraunhofer ISE presents an overview of MWT technologies and calls on manufacturers to “quickly bring these techniques to industrialisation”. Additionally back contact cells and modules are featured extensively with valuable contributions from IMEC/ECN and the ISFH.

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