N-type Solar Grade Silicon for Efficient p+n Solar Cells


Abstract: The EU white paper "Energy for the future" targets a rapid growth of the contribution of photovoltaics (PV) to energy supply and emission reductions in the EU. This growth must be accompanied by, and eventually be driven by, cost reduction through scale-up and technological advances. Solar cells based on crystalline silicon are expected to maintain a major share in PV production in 2010. The key action objectives of 3 GWp installed capacity in 2010 and module price below 1 Euro/Wp therefore require abundant availability of low-cost silicon feedstock, increased cell efficiency and a reduces amount of silicon used per Wp.

Nearly all commercial Si solar cells are based on off-spec (rejected and waste) material from the electronic industry together with Si that can be produced due to a temporary overcapacity for Electronic Grade (EG) Si in the industry. It is expected that the overcapacity for EG Si will have disappeared around 2004. For a growth rate of the PV market of 15 % there will at that time be a gap of around 3700 ton Si between demand and supply of Si feedstock for PV. Dedicated Solar Grade (SoG) Si production is under development, but there will not be production at a significant scale before 2006.

Currently, nearly all solar cells are processed from p-type silicon. No use is made of the additionally available highly n-doped off-spec Si. This highly n-doped Si may be used for solar cells if the dopant concentration can be reduced in a cost-effective way, and if a suitable cell processing sequence for n-type wafers is available. This project will make n-type silicon available as a new source of low-cost feedstock, with a capacity of 2000-3000 ton/y, sufficient for an additional 1.3-1.8 GWp cumulative installed PV power in 2010 This project will also develop and transfer innovative cell process technology for n-type wafers.

  • Fath, Peter - Project head
  • FB Physik
Funding sources
Name Project no. Description Period
Europäische Union
Further information
Period: 01.11.2002 – 31.10.2005