ATOMS that repair radiation damage as they wander through semiconductors
could lead to cheaper, more efficient and longer-lasting solar power cells, say
researchers in Israel.
快猫短视频s trying to make better solar cells have long been intrigued by a
complex semiconductor called CIGS (copper indium gallium diselenide). This
absorbs light more efficiently than silicon, works well in very thin films and
is surprisingly stable even when exposed to intense radiation鈥攆or example,
in space.
The mystery of the material鈥檚 stability has now been solved, says chemist
David Cahen at the Weizmann Institute of Science in Tel Aviv. The secret of CIGS
is its remarkable ability to repair itself. Cahen and his colleagues describe in
the current issue of Advanced Materials (vol 11, p 957) how they used
intense X-rays to probe CIGS and a material with very similar properties, copper
indium diselenide (CIS).
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The researchers found that some of the chemical bonds can be broken quite
easily, freeing copper atoms to wander through the crystals. They saw
radioactive copper-64 speeding through the semiconductor nearly 20 orders of
magnitude faster than materials added to silicon. 鈥淭he remarkable thing,鈥� says
Cahen, 鈥渋s that you can have a high-quality electronic material with these atoms
running around.鈥�
The material repairs itself, Cahen found, because the natural tendency of the
copper atoms to distribute themselves evenly means that they spread into damaged
spots in the crystal, where their presence fixes the problem. Solar cells made
from self-repairing semiconductors should last much longer than ones made
with conventional materials, such as silicon, which accumulate damage. Nobody
yet knows just how long such cells could survive, but at least one simulation
suggests they could keep on working for hundreds of years.
鈥淚t could well provide the stable, radiation-hard power supply for long-term
space missions,鈥� says Robert Tomlinson, a materials scientist at the University
of Salford in Manchester. 鈥淥nce it gets up there, it seems to last forever.鈥�
Until now, Cahen says, solar cell researchers have viewed the stability of
CIGS as 鈥渂lack magic鈥�. Now that the mechanism is understood, he expects the
field to move forward quickly.
At least one company, Siemens, markets CIGS solar cells. Franz Karg, a
physicist at Siemens Solar in Munich, says that these cells already generate
electricity more efficiently than other thin-film solar products. He鈥檚 intrigued
by Cahen鈥檚 findings, and agrees that understanding the self-repair mechanism
could encourage the development of even better semiconductors. Researchers can
design new semiconductors in the same family, he says, by swapping copper and
silver; indium, gallium and aluminium; or selenium and sulphur. Karg remains
cautious, however. Cahen鈥檚 claims are 鈥渧ery bold鈥�, he says, 鈥渂ut I鈥檓 willing to
be convinced.鈥�