New photovoltaics could assist re-charge of e-book readers

Scientists from Warwick University, in collaboration with spin-out company Molecular Solar, have created an organic solar cell that generates a sufficiently high voltage to recharge a lithium-ion battery directly, without the need to connect multiple individual cells in series.

According to a statement, modules of these high-voltage cells perform well in different light conditions, including partial shade, making them well matched to consumer electronic devices such as e-book readers, cameras and some mobile phones.

Organic photovoltaic (OPV) cells, the so-called ‘third generation’ of solar technology, offer opportunities due to the potential for cheap manufacture of lightweight, low-profile photovoltaics compatible with flexible substrates.

This new OPV technology is a claimed to be a significant breakthrough as scientists have addressed the problem of low-output voltage when the module is in low light levels or partial shading, taking an important step towards rolling out cheap OPV cells in low-power portable electronics.

The scientists, from the university’s Department of Chemistry, have also demonstrated a cell with an operating voltage of up to 7V, a figure higher than the 4.2V needed to power a standard lithium-ion battery.

This is said to be the first time these features have been demonstrated using ultra-high-voltage OPV cells.

Prof Tim Jones, one of the lead researchers at Warwick University, along with Dr Ross Hatton and Prof Mike Shipman, said: ‘We have taken a big step towards cheap-to-make solar chargers that can top up your devices whenever they are being used — both indoors and out.

‘A small lightweight solar charger no bigger than a credit card can be fitted to the battery of an e-book reader, for example, and constantly top it up with power while you are reading it — even if you are sitting inside on the sofa.

‘Alternatively, this kind of solar cell could be ideal for outdoor use as it is lightweight and portable.

‘The next step is to extend this technology outside the laboratory to make cheap OPV chargers available on a commercial scale through Molecular Solar.’

Molecular Solar is soon to launch a new round of fundraising to support the commercialisation of this technology.

The research is detailed in the paper ‘Ultra-high voltage multijunction organic solar cells for low-power electronic applications’ and was published in the journal Advanced Energy Materials.