New solar cell could capture more of the sun's energy

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Cambridge University scientists have developed a new type of solar cell that could capture significantly more of the sun’s energy than current silicon-based cells.

The solar cell could increase the maximum efficiency of solar panels by more than 25 per cent, according to the scientists from the university’s physics department.

Solar cells work by absorbing energy from particles of light, known as photons, which then generate electrons to create electricity.

Traditional solar cells are only capable of capturing part of the light from the sun and much of the energy of the absorbed light, particularly from the blue section of the light spectrum, is lost as heat.

This inability to simultaneously extract the full energy from the light spectrum means that traditional solar cells are incapable of converting more than 34 per cent of the available sunlight into electrical power.

Bruno Ehrler, lead author of a paper published on the subject in the journal Nano Letters, said: ‘Our solar cell uses inorganic and organic materials at the same time. In that respect it is a hybrid cell.’

The inorganic part is made from lead sulphide nanoparticles while the organic part is made from pentacene, a semiconducting material. 

Typically a solar cell is able to generate a single electron for every photon captured. However, by adding pentacene (in a process called singlet exciton fission) the solar cells can generate two electrons for every photon from the blue light spectrum.

‘Our solar cells use this process to make better use of the high-energy [blue] photons.’ 

This could enable cells to capture 44 per cent of the incoming solar energy. 

Ehrler said: ‘At the moment the cells are less efficient than conventional silicon solar cells. The paper proves that singlet exciton fission could be used to increase the current in solar cells.’ 

In order to achieve the maximum efficiency increase of 25 per cent, Ehrler said the cells need to be further developed. 

The team believes it is also possible to harness light from other parts of the spectrum.

Ehrler said: ‘The fission active organic part absorbs only in the blue region. There are other organic materials that undergo the fission process that use a different part of the spectrum.’