Sunday, August 10, 2014

Silicon Solar Cells Transformed

David Ginley, NREL

The limitation of silicon solar is silver for contacts which maxes out at around 5 TWatt.  Single cell efficiency maximizes out at around 29% efficiency. Bell Labs first cells were 6% efficient.  World installed solar is .3 TWatts by 2014.
Chinese dominate the PV market because they are the only ones who built silicon plants when supply reached scarcity.
Panasonic has a 25.6% efficiency HIT cell [mono thin crystalline silicon wafer surrounded by ultra-thin amorphous silicon layers] with contacts on the back .  SunPower has a 25% six inch cell built on their production line (but not in production yet).  Sharp also has a 25% cell.  
Theoretical efficiency of a single junction cell under 1000 sun concentration is around 33%.
25 year warranty but some companies are going to 35 with a possibility of 50 years and it is not the silicon cell with fails but the packaging or contacts.
Fifty cents per watt is the accessible price now.
University of New South Wales is working on thin film silicon, 20 microns rather than the 75 microns now used. 16.8% efficiency.
Tandem cells - silicon paired with other substances including  quantum dots, perovskites, theoretically to 34%
Multiple exciton generation (MEG) in colloidal silicon nanocrystals can theoretically go beyond the existing limits.  Two or three photons per carrier.

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