Tube-shaped solar cells could be woven into clothing

March 1, 2012 by Lisa Zyga, feature
Illustration of TiO2 nanorod arrays on carbon fibers fabricated by the “dissolve and grow” method. Image credit: Guo, et al. ©2012 American Chemical Society

( -- Titania semiconducting nanorods grown on the surface of carbon fibers look more like bristles on a tiny hairbrush than a solar cell, but the novel configuration could have several advantages over conventional flat solar cells. For instance, the flexible tube-shaped cells can capture light from all directions and even have the potential to be woven into clothing and paper for novel applications. But at the current stage of development, researchers are trying to find a simple, low-cost method for fabricating high-quality tube-shaped solar cells.

A team of researchers from the Georgia Institute of Technology in Atlanta, Georgia, and Xiamen University in Xiamen, China, have recently developed a new method for preparing uniform (TiO2) nanorods on carbon fibers. The new method has advantages over the commonly used sol-gel method, which requires and can cause cracks in the materials. The new study is published in a recent issue of the .

“This work demonstrates an innovative method for growing bunched TiO2 nanorods on flexible substrates that can be applied to flexible devices for energy harvesting and storage,” coauthor Wenxi Guo from the Georgia Institute of Technology and Xiamen University told

Fabricating tube-like is challenging due to the multiple steps involved, which include transforming pure Ti foil into TiO2 nanorods, coating carbon fibers with the nanorods, and uniformly arranging the nanorods on the fibers. As the researchers explain, an ideal solution for preparing TiO2 nanostructures on carbon fibers is to grow them directly on the fiber’s surface. They did so here using a “dissolve and grow” method for transforming Ti into vertically aligned single-crystal TiO2 nanorods on carbon fibers.

Scanning electron microscope images of TiO2 nanorod arrays uniformly covering the carbon fibers. Image credit: Guo, et al. ©2012 American Chemical Society

Then, in an attempt to further improve the device’s performance, the researchers used an “etch and grow” method to etch the nanorods into rectangular bunched arrays using a hydrothermal treatment with hydrochloric acid.

After assembling the nanorod-covered carbon fibers as photoanodes in tube-shaped dye-sensitized solar cells (DSSCs), the researchers experimentally tested the solar cells’ performance. The results showed that the rectangular bunched nanorod configuration achieved an energy conversion efficiency of 1.28%, compared with 0.76% for the unbunched configuration. The researchers attribute the difference to the larger surface area of the bunched , which enables more dye molecules to be adsorbed, resulting in more electron excitations.

The large surface area gives the tube-shaped solar cells the ability to capture light from all directions, which could make them attractive for applications under intensively forced sunlight. Besides solar cells, the method for growing TiO2 nanowires on carbon fibers could be extended to fabricating photocatalysts and lithium ion batteries. But perhaps the most unique application would be weaving them into fabrics.

“In the future, we may introduce or other carbon materials as the counter electrodes for this configuration,” Guo said. “In this case, we can fabricate DSSCs just based on carbon materials and TiO2 that are promising for cloth and paper applications. We may also plan to do some hybrid work to acquire different sources of energy based on this configuration.”

Explore further: Researchers prepare cheap quantum dot solar paint

More information: Wenxi Guo, et al. “Rectangular Bunched Rutile TiO2 Nanorod Arrays Grown on Carbon Fiber for Dye-Sensitized Solar Cells.” Journal of the American Chemical Society. DOI: 10.1021/ja2120585

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3.7 / 5 (3) Mar 01, 2012
I believe the word you were looking for is "woven."
5 / 5 (3) Mar 01, 2012
I would like to have sails made of it in my sailing boat. A multidirectional solar fabric could harvest both the wind and the solar energy at the same time. Sails offer a huge area and could provide significant electricity to an electrical propeller. Using both at the same to navigate faster when possible, and when there is no wind you could still orient the sails to face the sun for best performance. When the boat is in the harbour it could still be charging the batteries, and then sale the remaining electricity to the network.
not rated yet Mar 01, 2012
Javjav, don't overestimate the power of a solar cell - even the size of a sail. Be lucky if you make half a knot out of this. And most certainly you don't want your boat under full sails within the harbor to catch a light breeze and be pushed to the quay wall. Finally going for a sail would be - next maybe only to an alpinists tent - the most rugged application for such a fabric ;)

Not saying no, just sayin' it's going to be hard.
not rated yet Mar 01, 2012
half a knot? please don't sub-estimate solar power.

Maybe not today, but it is not a crazy idea if they manage to improve efficiency, which is the key aspect. For example, the solarimpulse plane can deliver more than 15Hp (as an average on day hours), by using a 200 m2 solar surface with 20% efficient cells.

Under similar efficiency, a 12 meter boat could use more than 120 m2 in full sail (gennaker included). If it could obtain 10Hp it could mean 3 knots additional speed or more, which is a very significant speed for a sailing boat.

The problem is that a 20% efficiency is not possible with this fabric, but the big advantage of a boat is that it can bring much heavier batteries than a plane. More weight translates in slower acceleration, but the cruise speed is not be affected too much. Just recharge batteries when the wind is enough, and use batteries plus direct solar power when there is not.
not rated yet Mar 01, 2012
For example, the solarimpulse plane can deliver more than 15Hp (as an average on day hours), by using a 200 m2 solar surface with 20% efficient cells.

Under similar efficiency, a 12 meter boat could use more than 120 m2 in full sail (gennaker included). If it could obtain 10Hp

Solarimpulse: horizontal.
Sail: vertical

See the problem? A sail would get very slanted sunlight or only ambient light. Much lower energy output. (Not that it might not be worth it to run some basic on board systems - but you won't get 10hp. Maybe 2. Maybe.
1 / 5 (1) Mar 01, 2012
"But perhaps the most unique application would be weaving them into fabrics."

Yet again another laboratory curiosity looking for a commercial use. 1.28% efficiency wheeeee!
not rated yet Mar 01, 2012
Thanks for the heads up. Nice estimate. However I assume that you shadow like a third of your sails on a fore-and-aft rigged boat reducing your available surface. As pointed out antialias you got a bad angle of incidence during the better part of the day - but then again this kind of cell might work as well (or in this case "as bad") with diffuse light.

If you make hullspeed under sails it won't help anyways. However it would be fun if you could make a little speed without proper wind ;-)
not rated yet Mar 01, 2012

Solarimpulse: horizontal.
Sail: vertical

See the problem? A sail would get very slanted sunlight or only ambient light.

Have you read the article? the new thing is the multidirectional cell thanks to its micro-cylinders, which is exactly what you need when the sail surface is randomly oriented (better said oriented as required for a desired runway).

In any case, in a sailing boat most of the sail surface is never vertical (specially the gennaker ), and the sun is only on top at midday in the worst case, and the sea water act as a giant mirror reflecting significant light to the sails (in this case vertical is better). Altogether we could estimate that the average incident light vector angle will not be too far from 45º (do not forget that the fabric have two sides).
In my opinion, the combination of multidirectional cells and the use of batteries should provide extra hps.
However, I recognize that they still need to improve the efficiency for practical use.

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