Researchers develop self-healing solar cells
Dye-sensitized solar cells already have many potential advantages over silicon. Now they may heal themselves, too.
Wed, Aug 21, 2013 at 01:25 PM
Dye-sensitized solar cells have long been held up as a promising alternative to silicon.
Dye-sensitized solar cells, or DSSCs, use a number of cost-effective, readily abundant materials for their base — from plastic to ceramics to metal or glass. They generate electricity due to an interaction between light and a cheap pigment painted on titanium dioxide. They have the potential to generate electricity at low levels of light, for example in partial shade or on cloudy days. And they have been shown to reach efficiencies not too far off from their mainstream silicon counterparts.
Until now, however, these cells have been held up by concerns about chemical stability in adverse weather conditions. Here's how the Wikipedia entry on dye-sensitized solar cells describes the problem:
The major disadvantage to the DSSC design is the use of the liquid electrolyte, which has temperature stability problems. At low temperatures the electrolyte can freeze, ending power production and potentially leading to physical damage. Higher temperatures cause the liquid to expand, making sealing the panels a serious problem.
Now Professor Orlin Velev and Dr. Hyung-Jun Koo, solar energy specialists at NC State University, have published a paper in Scientific Reports describing a new type of self-healing, dye-sensitized solar cell. Like the makers of a self-healing artificial leaf that produced hydrogen for fuel cells, Velev and Koo looked to nature for a solution to the degradation problem:
“Organic material in DSSCs tends to degrade, so we looked to nature to solve the problem,” Velev said. “We considered how the branched network in a leaf maintains water and nutrient levels throughout the leaf. Our microchannel solar cell design works in a similar way. Photovoltaic cells rendered ineffective by high intensities of ultraviolet rays were regenerated by pumping fresh dye into the channels while cycling the exhausted dye out of the cell. This process restores the device’s effectiveness in producing electricity over multiple cycles.”
Whether or not this solves the physical damage to solar cell structure caused by expansion or freezing of the liquid, or just the degradation to the dye itself, is not entirely clear from the abstract or the press release. Either way, it seems that this biomimetic approach to improving DSSC resilience is just a logical extension of the inspiration behind the cell itself.
As Michael Grätzel, inventor of the DSSC, explains in this video, the whole concept of a DSSC is based on mimicking the natural, molecular process of photosynthesis in a leaf.
Doubtless there will be plenty of other challenges ahead for mainstreaming DSSCs into the solar market. But as the video explains, they are already being made on a large scale for gadgets and other mobile applications (in a wind-powered factory no less!), and several companies are looking to develop them for building applications. (For example, embedded in window glass.)
Making sure that these cells can maintain their capacity over a longer period of time may well be a huge leap forward for this promising technology.
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