Micron-sized solar cells

PORTLAND, Ore. — Sandia National Labs has harnessed silicon's natural tendency to grow into islands and used micro-electro-mechanical systems techniques to free those islands into the world's smallest solar cells.

Sandia claims the micron-sized solar cells are as efficient as their wafer-sized big brothers, but consume only one hundredth the amount of semiconductor.

Rather than force solar cells to grow across an entire wafer in a perfect crystalline lattice, and throw the whole wafer away if any imperfections develop, Sandia National Labs has found that smaller is better.

Measuring just 100 microns round and just 14-to-20 microns thick—including electrodes—the tiny solar cells resemble snowflakes, but can be ganged together in parallel to provide whatever current generation capacity required by an application.

In addition, they can also be wired in series to generate high voltages that are impossible with conventional solar cells. In the space required for 12 volts from a traditional solar cell, hundreds of volts can be generated by micron-sized solar cells wired in series.

Sandia also claims their solar cells small size would allow them to be affixed to flexible surfaces, even clothing, turning almost any surface into a solar panel.

In tests, Sandia demonstrated that a conventional pick-and-place robot can assemble about 130,000 of the tiny solar cells per hour over several square meters at a cost of approximately one-tenth of a cent per cell.

Funding was provided by the Department of Energy's Solar Energy Technology Program and Sandia National Laboratory's Directed Research & Development program.