Hydrogen passivation of multicrystalline silicon solar cells

The use of hydrogen for passivation of multicrystalline silicon in solar ce ll technology is described. Three kinds of hydrogen incorporation into mc-S i solar cells have been evaluated: hydrogen diffusion out of a SiN-layer (S iN:H), low-energy hydrogen ion implantation (HII), and remote plasma hydrog en passivation (RPHP). Best results were obtained by RPHP, whereas using HI I, damage exceeded the passivation effect to some extent. While SiN:H passi vates more the grains, RPHP acts particular on grain boundaries. Combining hydrogen passivation by SiN:H and RPHP leads to optimal bulk passivation. W e have investigated the influence of RPHP to various mc-Si materials by sol ar cell and diffusion length measurements. CVD layers and ribbon material s how the strongest increase in performance. A boost of up to 77.0 mV in the open-circuit voltage and 2.0% in the efficiency of solar cells has been ach ieved. Electromagnetically casted Si has shown an improvement of 2.1% in ef ficiency after RPHP treatment. But even mc-Si of higher quality, like mc-Ba ysix and Eurosolare mc-Si could be rectified by RPHP. Applying a standard c ell process for material assessment efficiencies of 16.9% have been obtaine d including a RPHP step. Thus the potential for high-efficiency mc-Si solar cells is shown. (C) 1999 Elsevier Science S.A. All rights reserved.