Singlet fission (photo-voltaics)

Current photo-voltaic (PV) cells - e.g. solar panels for 'green' energy generation - have a quite low efficiency limit. If a high energy (that's to say high frequency, or short wavelength) photon falls onto a PV cell, it generates the same electrical energy as a low energy photon. The 'excess' energy of a high-energy photon is 'lost' as heat. This puts the theoretical limit of efficiency at around 33%.

In 1965, a new possibility for increasing efficiency was observed in a relatively simple hydrocarbon called Tertracene ( C₁₈H₁₂ )

It was suggested that the phenomenon could be explained by 'Singlet Fission'. Singlet systems are compounds in which all electrons are paired. But, via high energy photons, in Tetracene, they can convert into 'triplet systems - which have two unpaired electrons.

This has now also been observed in Pentacene and several other compounds.

It's hoped that the phenomenon could be exploited to create new types of PV cells which could theoretically have efficiencies of up to 60% - a large improvement on current systems - with profound implications for green energy generation.

However, an exact description of the quantum physics underlying the 'Singlet Fission' mechanism has not yet been found.

Further technical info : Wikipedia and Cavendish Laboratory, UK

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