Interested In Science?

In the latest edition of the journal Science there features a report on the successful preparation of a plastic photovoltaic cell that reaches efficiencies of 6.5%, a record for this type of device. Alan Heeger and colleagues from the University of California, Santa Barbara, in collaboration with scientists from Gwangju Institute of Science and Technology, have sandwiched two polymers together around a layer of transparent titanium oxide, to create a ‘tandem cell’.

The reason the efficiency of this device is so high is that the two different polymers absorb in different regions of the solar emission spectrum i.e. electromagnetic radiation emitted from the sun, meaning they can collect more light energy. The titanium oxide layer is completely transparent to these energies of light, and thus allows the rear polymer to absorb light that isn’t absorbed by the front polymer. The titanium oxide is an integral component because of this transparency.

‘Tandem cell architectures’ have been attempted before but without this high efficiency; partly due to the two polymers absorbing the same energies of light, partly due to poor processing methods allowing the polymers to mix, but also down to the incorporation of only a semi-transparent layer sandwiched between the layers, severely inhibiting the absorption capabilities of the rear plastic film.

Schematic of the tandem cell, taken from Science 2007 317 222-225

Some scientists believe that 6.5% effective power conversion is likely beatable in the very near future, with figures closer to 10% being rumoured. This new tandem cell could herald a break-through in the technology. Due to the nature of the materials that constitute these devices, their production is cheap, with large flexible surfaces being the obvious goal.

Keep checking interestedinscience.com for any updates on this subject.

For more on this topic, see gizmodo.com or technologyreview.com

See {Science 2007 317 222-225} for the original article.

interestedinscience.com ©  2007