A team of researchers in China says it has found way to make solar panels work effectively in both rain and shine, by coating them with a layer of electron-rich graphene that can generate electricity from both sunlight and from salt ions in rain water.
A report in the journal Angewandte Chemie says that a team led by China’s Ocean University in Qingdao devised the method using a highly efficient dye-sensitized solar cell, coated with a thin film of graphene.
Graphene – an easy to produce, two-dimensional form of carbon in which the atoms are bonded into a honeycomb arrangement – is characterised by its unusual electronic properties, being rich in electrons that can move freely across the entire layer.
These properties allow electrons to move freely (delocalise) and make it a negatively-charged material when in solution.
When rainwater falls onto a solar panel – a condition that traditionally makes them unproductive – the droplets contain positively-charged salt ions of sodium, calcium and ammonia, which can bind with the surface of the graphene layer.
The interaction results in a double-layer which causes the potential energy difference between the positively- and negatively-charged layers – enough to drive the delocalised electrons into producing a voltage and current.
According to this report, the team was able to generate electricity in the hundreds of microvolts range and achieve a solar-to-electricity efficiency of 6.5 per cent from the prototype graphene panel.
The primary challenge facing the team is the relatively low concentrations of salt ions in rainwater compared to the salt solutions prepared in the lab, which will make it difficult for the panel to produce large quantities of electricity.
They are currently working on modifying the technology to handle a variety of ion mixtures that can be contained in rainwater.
The team hopes the results can be incorporated into future solar cell designs and open up new ideas for alternative electricity generating capabilities for solar cells.