Technology

Solar-Cells: wafer-thin, flexible and effective

Korean engineers create ultra-thin solar cells, flexible enough to allow wrap as a foil to a needle. This extremely flexible solar cells offer new versatility. You can even stick it on a pair of glasses.

“Our photovoltaic cell is about a micrometer-thin,” said Jongho Lee, senior engineer at the South Korean Gwangju Institute of science and technology, short GIST in Gwangju. Thus, the cells are thinner than a human hair. The Korean research were now published in the journal applied physics letters of the American Institute of physics.

Previously on the market solar cells are clearly chunky, usually a hundred times thicker and thus also much less malleable, which significantly reduces their applications. Even the thinnest photocells are still two to four times as thick as the ultra thin solar cells developed by the Koreans.

However, the desire is spread so thin and still powerful cells. So also the U.S. Army on such cells research projects, to build them as energy donor in uniforms. Previous prototypes should be 1000 times thinner than a sheet of paper.

Base material of cells is gallium arsenide

The newly developed solar modules consist of the gallium arsenide semiconductor material. The cells were stamped directly on a flexible substrate without the use of an adhesive. As a next step, the cells in the cold welding process by means of pressure at 170°C were applied to the electrode.

wafer-thin flexible and effective
The solar cells are about a micrometer-thin and flexible enough to allow even wrap to a needle. They can be glued as energy donor but also on glasses or used in fabric. Photo: GIST

However, the top layer of the material called photoresist, which acted as a kind of temporary adhesive, melted. This layer was later removed, which resulted in a direct binding of metal to metal. The bottom metal layer serves as a kind of reflector to redirect back scattering of protons directly to the solar cell.

The scientists tested the efficiency of the cells by converting sunlight into electrical energy. Their efficiency was comparable with those thicker photo cells.

Thin cells with high power density

The Korean researchers found in flexibility tests that the cells to items can be wrap with a thickness of up to 1.4 mm. The team carried out a numerical analysis and noted that the cells learn only a quarter of stress compared to cells with a thickness of 3.5 micrometers.

“The cells are less brittle and much powerful, thus bending if not better”, explains Lee.

This opens up many new application possibilities, such as the use of data glasses, fitness trackers or smart watches, which then supply them with energy. The paper-thin solar cells can sew up in clothing, to provide for example, power for smartphones.

GIST
The GIST-Institut in South Korea deals particularly with flexible solar cells, which are also used for medical purposes. Photo: GIST

Research on ultra thin cells in EU

Research groups reported thickness of only about one micrometer in other countries also the development of solar cells with one. German researchers are working on ultra thin and flexible solar cells. This is, for example, organic solar cells, the, because cheap plastic, can be almost any shape. Manufacturer is the Nuremberg company Belectric Konarka, which establishes such cells via printer, similar to how newspapers. The solar specialists of ZSW in Stuttgart to develop ultra-thin solar cells.

Until the end of February this year engineers of Massachusetts reported of technology (MIT) the development of the world’s thinnest solar cell Institute in Boston. It is so easy that it even brings a bubble to burst.