Collecting the sun's energy: Novel electrode for flexible thin-film solar cells

Apr 19, 2011

Conventional silicon-based rigid solar cells generally found on the market are not suitable for manufacturing moldable thin-film solar cells, in which a transparent, flexible and electrically conductive electrode collects the light and carries away the current. A woven polymer electrode developed by Empa has now produced first results which are very promising, indicating that the new material may be a substitute for indium tin oxide coatings.

The scarcity of raw materials and increasing usage of rare metals is making electronic components and devices more and more costly. Such rare metals are used, for example, to make the transparent electrodes found in mobile phone touchscreen displays, liquid-crystal displays, organic LEDs and thin-film . The material of choice in these cases is (ITO), a largely transparent mixed oxide. Because ITO is relatively expensive, however, it is uneconomic to use in large area applications such as solar cells.

The search for alternatives

Indium-free transparent do exist, but with demand for them increasing they too are tending to become scarce. In addition, the principal disadvantages such as brittleness remain. The search for alternative coatings which are both transparent and electrically conductive is therefore intense, with materials such as conductive polymers, carbon nanotubes or graphenes coming under scrutiny. Carbon-based electrodes, however, generally show excessive surface resistance values which make them poor electrical conductors. If a metallic grid is integrated into the organic layer, it reduces not just its resistance but also its . If a solar cell made out of this material is bent, the electrode layers break and are no longer conductive. The challenge thus consists of manufacturing flexible yet stable conductive substrates, ideally in a cost-effective industrial rolling process.

One solution: woven electrodes

One particularly promising possibility is the use of a transparent flexible woven polymer, which Empa has developed together with the company Sefar AG in a project financially supported by the Swiss Commission for Technology and Innovation (CTI). Sefar, which specializes in precision fabrics, is able to produce the woven polymer economically and in large quantities using a roll to roll process similar to the way newspapers are printed. Metal wires woven into the material ensure that it is electrically conductive. In a second process step the material is embedded in an inert plastic layer which does not, however, completely cover the metal filaments, thus retaining its conductivity. The electrode which results is transparent, stable and yet flexible. The Empa researchers then applied a series of coatings to this new substrate to create a novel organic solar cell whose efficiency is compatible to conventional ITO-based cells. In addition, the woven is significantly more stable when deformed than commercially available flexible plastic substrates to which a thin layer of conductive ITO has been applied.

Explore further: Researchers make major advances in dye sensitized solar cells

add to favorites email to friend print save as pdf

Related Stories

Copper Nanowires Enable Bendable Displays, Solar Cells

Jun 01, 2010

(PhysOrg.com) -- A team of Duke University chemists has perfected a simple way to make tiny copper nanowires in quantity. The cheap conductors are small enough to be transparent, making them ideal for thin-film ...

Nanometer Graphene Makes Novel OLEDs Display

Mar 10, 2010

Researchers at Stanford University have successfully developed brand new concept of organic lighting-emitting diodes (OLEDs) with a few nanometer of graphene as transparent conductor. This paved the way for ...

Recommended for you

Nanomaterial outsmarts ions

Apr 22, 2014

Ions are an essential tool in chip manufacturing, but these electrically charged atoms can also be used to produce nano-sieves with homogeneously distributed pores. A particularly large number of electrons, ...

User comments : 0

More news stories