Thicker than 200 um ‘Lambertian’ light trapping

a-Si:HHydrogenated Amorphous Silicon Si EcEc EvEv EFEF E t n Int. X Dark

Recombination on interface states Recombination on metallic contact

Quantum mechanical Electron tunneling effect Thermal effect

Contacts resistance

Heavy doping imposes an upper limit on lifetime according to t A = 1/C A N A 2, where t A is the Auger-limit lifetime. C A is the Auger coefficient Auger recombination involves three particles: an electron and a hole, which recombine in a band-to-band transition and give off the resulting energy to another electron or hole. t for GaAs is of the order of tens of ns

Tyagi, M. S. and R. Van Overstraeten, Solid State Electron. 26, 6 (1983)

The growth in silicon production hasn't kept pace with the rise in solar power. "It takes about two or three years to add capacity". The shortage has been severe enough to drive up silicon prices to more than 10 times normal levels, to $450 a kilogram. First silicon solar cell to achieve the milestone of 25 percent efficiency. University of New South Wales' ARC Photovoltaic Centre of Excellence.