Metallisation and interconnection of polycrystalline silicon thin-film solar cells on glass superstrates

摘要

Thin-film photovoltaics seem set to become a large part of future photovoltaic production worldwide, due to the fact that thin-film photovoltaic modules have the potential to be manufactured for a significantly lower cost per peak Watt of photovoltaic electricity produced than traditional wafer-based photovoltaic modules. Of particular interest are polycrystalline silicon (poly-Si) thin-film photovoltaic devices on foreign supporting superstrates such as glass, because they combine the best features of wafer-based modules (long-term stability, vast manufacturing experience) with the best features of thin-film modules (lower materials cost, and monolithic construction techniques).Since polycrystalline silicon thin-film solar cells on glass superstrates are a relatively recent development in photovoltaics, there remains much scope for the investigation and implementation of novel metallisation and interconnection schemes. This thesis is concerned with the invention and development of metallisation and interconnection schemes for this new photovoltaic material, poly-Si on glass.In this thesis, several new metallisation and interconnection schemes for poly-Si solar cells on glass superstrates were invented and investigated:- The sequential metallisation and interconnection scheme, which is based on cells with interdigitated n-type and p-type contacts, and subsequent inter-connection of individual cells.- The metal-free interconnection scheme, which relies on laser-doping of regions of the silicon film to interconnect adjacent cells, and does not require metal contacts.- The spanning-gap interconnection scheme, which involves laser-scribing of the silicon film, and overdoping one sidewall of each laser scribe, then connecting adjacent cells by filling the laser scribe with metal.- The wrap-over interconnection scheme, which employs laser scribing and insulating and conductive laser-scribe sidewalls, and a metal layer whichinterconnects adjacent cells.Also investigated was the specific contact resistance of each type of metal-semiconductor contact used in the various interconnection schemes.The various interconnection schemes were developed to different levels of completion. The sequential metallisation and interconnection scheme yielded fully functioning mini-modules with good efficiencies. The wrap-over interconnection scheme made it to the proof of concept stage, while the other two schemes did not reach completion due to various technical difficulties and time constraints.