19.8% efficient "honeycomb'' textured multicrystalline and 24.4% monocrystalline silicon solar cells

Multicrystalline silicon wafers, widely used in commercial photovoltaic cell production, traditionally give much poorer cell performance than monocrystalline wafers (the previously highest performance laboratory devices have solar energy conversion efficiencies of 18.6% and 24.0%, respectively). A substantially improved efficiency for a multicrystalline silicon solar cell of 19.8% is reported together with an incremental improvement in monocrystalline cell efficiency to 24.4%. The improved multicrystalline cell performance results from enshrouding cell surfaces in thermally grown oxide to reduce their detrimental electronic activity and from isotropic etching to form an hexagonally symmetric "honeycomb'' surface texture. This texture reduces reflection loss as well as substantially increasing the cell's effective optical thickness by causing light to be trapped within the cell by total internal reflection. (C) 1998 American Institute of Physics. [S0003-6951(98)00840-7].