Ultrahigh Efficiency Multiband Solar Cells Final Report forDirector's Innovation Initiative Project DII-2005-1221

摘要

The unique properties of the semiconductor ZnTeO were explored and developed to make multiband solar cells. Like a multijunction cell, multiband solar cells use different energy gaps to convert the majority of the solar spectrum to electrical current while minimizing losses due to heating. Unlike a multijunction cell, this is accomplished within a single material in a multiband cell. ZnTe{sub 1-x}O{sub x} films with x up to 2% were synthesized and shown to have the requisite unique band structure (2 conduction bands) for multiband function. Prototype solar cells based on an n-type ZnTe{sub 1-x}O{sub x} multiband top layer and a p-type ZnTe substrate were fabricated. Contacts to the cell and the series resistance of the substrate were identified as challenges for good electrical performance. Both photovoltage and small photocurrents were demonstrated under AMO illumination. A second semiconductor system, GaN{sub x}As{sub 1-y-x}P{sub y}, was shown to have multiband function. This alloy system may have the greatest potential to realize the promise of high efficiency multiband solar cells because of the relatively advanced technology base that exists for the manufacturing of III-V-alloy-based IC and opto-electronic devices (including multijunction solar cells).