2006 R&D 100 Winner

A seemingly unavoidable tradeoff between cost and power efficiency has, historically, relegated the solar cell to niche markets such as space power, military applications, and relatively low-cost, low-efficiency uses such as off-grid power. All of that has changed with the High-Efficiency Multiband Semiconductor Material for Solar Cells, developed by Wladyslaw Walukiewicz and Kin Yu at Lawrence Berkeley National Laboratory, Calif. With its combination of low cost and full-spectrum efficiency, the multiband semiconductor demonstrates that this trade off is not inevitable and opens a path forward for them development of photovoltaic systems as a major source of electric power.

The new semiconductor material, a highly mismatched alloy (HMA), has multiple, tunable band gaps for use in high-efficiency, single-junction, full-spectrum solar cells. HMA semiconductors are ideally suited for use in a new type of highly efficient, easy-to-manufacture solar cell, the multiband solar cells (MBSC). An MBSC using an HMA with three bands has a maximum theoretical efficiency of 63%—more than four times greater than the 15% typical of high-quality silicon cells now on the market. Using the band anticrossing theory of HMAs developed by the Berkeley Lab team, MBSCs using a four-band HMA with a maximum theoretical efficiency of 72% can also be realized.

Semiconductor material

Lawrence Berkeley National Laboratory

Originally published in R&D Magazine, September, 2006