New approach to ink boosts solar-cell efficiency to more than 17%
By Margery Conner, Technical Editor -- EDN, October 24, 2008
Advances in solar-cell efficiency usually focus on the cell itself: In a monocrystalline-silicon-solar cell, the efficiency can be as high as 18 or 19%. However, these high figures don’t account for the efficiency—or inefficiency—of the collector electrodes, which are screen-printed onto the silicon emitter that forms the top of the solar cell. This surface collects the sunlight and converts it to current. However, current solar inks suspend within them silver conducting particles and typically achieve line widths of 120 to 175 microns—wide enough to block sunlight and, hence, reduce efficiency. If the lines were any narrower, more surface area of silicon would be exposed to the sun.
Five Star Technologies has addressed this problem by using a hydrodynamic-cavitation process instead of a traditional milling process to create the silver particles in its new ElectroSperse S-540 ink. The new technology yields finer, size-controlled silver particles with lines as narrow as 80 to 100 microns in the screen-printing process. The company claims that the technology can enhance solar-panel efficiency by as much as 9% when more and narrower lines contact the panel’s silicon emitter. Tests at the Georgia Institute of Technology revealed that the monocrystalline cells that Five Star produced with ElectroSperse S-540 ink had cell efficiencies of 17.4%.
