HIGH-EFFICIENCY CRYSTALLINE SILICON SOLAR-CELLS

The efficiency of crystalline silicon solar cells under non concentrated light has increased since 1983 from 17% to over 23%, a large gain for a relatively mature technology. Improvements have been made in several areas, notably in the trapping of weakly absorbed infra red radiation within the silicon, in surface passivation and in maintenance of high carrier lifetimes during processing. These and other improvements are discussed, and it is concluded that efficiencies of 25% are possible with current technology. However, improved methods of surface passivation are required for further progress towards the limit for conventional cells of around 29%. There has also been significant progress in efficiencies on lower cost polycrystalline silicon substrates to close to 18%. Cells with efficiencies above 20% seem possible by adapting the high efficiency techniques mentioned above to thin polycrystalline substrates. Crystalline silicon remains the most attractive semiconductor for solar cell applications.