HIGH-CONDUCTIVITY LAYERS OF MICROCRYSTAL N-TYPE SILICON FOR TANDEM SOLAR-CELLS BASED ON AMORPHOUS-SILICON - FABRICATION, STRUCTURE, PROPERTIES, AND APPLICATIONS

High-conductivity layers of microcrystal n-type silicon have been prod uced by means of an rf discharge, (13.6 MHz) in a plasma in a multicha mber system for fabricating solar cells. Variation of the hydrogen con tent (H2:SiH4) and the phosphine content (PH3:SiH4) in the gas phase, of the total pressure, and of the discharge power revealed the conditi ons under which layers of maximum conductivity (approximately 80 S/cm) form. The resulting layers have a complex substructure: crystallites about 10 nm in size combined into spherical clusters on the order of 1 00 nm in size. Essentially no amorphous phase was found. The replaceme nt of the amorphous n-type layer by a microcrystal layer at the n-p ju nction results in a pronounced decrease in the contact resistance. The use of such junctions in p-i-n-p-i-n tandem solar cells increases the ir efficiency as the result of an increase in the photocurrent and in the filling factor of the current-voltage characteristic.