Cleveland, Ohio Five Star Technologies, a supplier of fine particle dispersions for functional inks, has announced its ElectroSperse S-series solar inks for use in crystalline silicon photovoltaic cells. To be unveiled at Solar Power International 2008 in San Diego, October 13-16, the inks were developed to solve a key challenge facing solar cell producers, maintaining consistent electrical contact with emitter layers, which could improve manufacturing yields and boost overall cell efficiency.
The S-500 series of silver-based conductive inks will allow solar cell makers to layout front-side grid lines as narrow as 80-100 microns, which is much thinner than the 120-175-micron width of conventional contacts, said Five Star.
The company's S-600 products low-bow, lead-free, aluminum-based pastes intended for back surface field layers have been designed to co-fire at temperatures compatible with the S-500 silver inks, which should simplify the latter's adoption.
Five Star uses a hydrodynamic cavitation process that enables the company to produce inks and pastes with high silver and glass particle uniformity and particle sizes in the low to sub-micron range. The upshot: finer lines in screen printing for more consistent emitter contact.
According to recent tests conducted by the Georgia Institute of Technology, monocrystalline cells produced with S-540 demonstrated cell efficiencies of 17.4%, fill factors approaching 78%, virtually no variation in performance at firing profiles differing by as much as 20 degrees C, and almost ideal n-factor values, implying extremely low leakage current, said Five Star.
Initial grades of the inks are intended for screen printing applications, but Five Star says it can control rheology to match a variety of printing processes, including non-contact dispensing approaches. For all processes, the ability to print finer dimensions should give cell designers greater flexibility in adding more efficient collection configurations, according to the company.