Monday, November 23, 2009

An Idea: Percolating to the Surface

If one cannot see the dynamical relation toward "localization of the energy" it will never make sense how such energy can be used to advance sustainability. While they are close in the thinking, the idea, still remains apart from acknowledgement of the substance of the proposal.

Thin-Film Solar with High Efficiency

Solexant is printing inorganic solar cells with nanomaterials.

Solar cells made from cheap nanocrystal-based inks have the potential to be as efficient as the conventional inorganic cells currently used in solar panels, but can be printed less expensively. Solexant, a company in San Jose, CA, is currently manufacturing solar cells to test the technology. In order to compete with other thin-film solar companies, Solexant is banking on simpler, cheaper printing processes and materials, as well as lower initial capital costs to build its plants. The company expects to sell modules for $1 per watt, with efficiencies above 10 percent.
Nanocrystal solar: The solar cells at top were made on a roll-to-roll printer from an ink consisting of the rod-shaped inorganic semiconducting nanocrystals shown below. The cells were printed on a flexible metal foil and will be topped with a glass plate.
Credit: Solexant

The company has licensed methods for growing nanocrystals and making them into inks from Paul Alivisatos, professor of nanotechnology at the University of California, Berkeley and interim director of the Lawrence Berkeley National Laboratory. (Alivisatos is on Solexant's board of directors.) Alivisatos says the advantage of these materials is their potential to combine low cost with high performance. Solar cells made from crystalline silicon are efficient at converting sunlight into electricity, but they're expensive to manufacture. To bring down the cost, companies have been developing thin-film solar cells from semiconductors that don't match crystalline silicon's performance but are much less expensive to make.

Solexant's goal is to make cheap thin-film solar cells with relatively high efficiencies. It would not disclose what the nanoparticle inks are made of, but the company says they are suspensions of rod-shaped, semiconducting nanocrystals that are four nanometers in diameter and 20 to 30 nanometers long. The Solexant cells are printed on a metal foil as the substrate. Nanocrystal films are simple to print but have poor electrical properties. Electrons tend to get trapped between the small particles. "The trick with these cells is how to deposit the materials on the fly in a way that makes a very conductive surface," which in turn ensures decent light-to-electricity conversion, says Alivisatos. Solexant begins with nanocrystals because they're easier to print, and heats them as they're printed, causing them to fuse together into larger, high-quality microcrystals that don't have as many places for electrons to lose their way.
The remaining parts of the solar cell, including the electrical contacts and a light-absorbing layer, are also printed on the flexible metal films. This process allows Solexant to print very large areas. When complete, the cells are cut and then topped with a rigid piece of glass.



I wanted to keep a record of these links for examination so besides the blog posting here, a direct link to the authors of this record keeping.


Evidence of Solar PV, Battery and Conservation Advancements


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Electric Vehicles





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