18% efficient polycrystalline silicon solar cells

Over the past 7 yr, there has been marked improvements in crystalline silicon solar cell performance, with the highest independently confirmed cell efficiency increasing from 17.1% to 24.2%. Work directed at transferring some of these improvements to polycrystalline silicon cells is described. Applying a high-efficiency crystalline cell sequence has given efficiencies as high as 17.8% with the addition of a phosphorous pretreatment step and modifications of a rear Al alloying step and cell processing temperatures. Surface texturing is identified as an important area requiring attention to obtain the highest possible efficiency. Laser texturing has given the best results to date for polycrystalline substrates. Results are described for a laser-textured, laser-grooved cell processing sequence with the potential to produce polycrystalline cells having efficiencies well above 18%