Molecular Solar claims record voltage for photovoltaic cells

The company’s most recent advance in the development of organic photovoltaic (OPV) cell technology is the realisation of cells with open-circuit voltages in excess of 4V, which Molecular Solar believes is a record for an OPV device.

This record voltage could see the highly flexible, low-cost solar cells transferred to consumer electronics.

‘If you want to get a high voltage in solar devices, you need to stack lots of these cells on top of each other. What we’ve done is exactly that but we’ve achieved a relatively high voltage for relatively few stacks,’ said Dr Ross Hatton, inventor of the technology and co-founder of the Warwick University spin-out.

Hatton told The Engineer that rather than using a conventional semiconductor such as silicon to harvest the light and transport the electrons, the team instead used highly congregated small molecules made up of various derivatives of phthalocyanines.

The device created by Molecular Solar used four stacks (or junctions) and produced a voltage similar to the highly efficient gallium arsenide solar cells, which Hatton said are relatively expensive in comparison.

‘The high voltage of these particular solar cells means that an individual cell could be used to recharge a lithium battery directly without having to connect individual cells up in series,’ Hatton said.

In terms of production, Hatton said that the advantages of molecular solar technology is that the molecules are deposited by thermal evaporation.

‘Which means that we can put down very thin films,’ he said. ‘The total device thickness is only 100–150nm.’

The solar technology could be applied to the Amazon Kindle, due to its relatively low energy requirements. Hatton told The Engineer that the 2 x 2cm cells could be placed on the cover of the Kindle and negate the need for mains power.

He said: ‘Electronic ink applications are where we see our first generation of technology being applied because they don’t use any energy when the image is projected on the screen. They use energy to change the image but not when it is projected.’

Molecular Solar believes there could be potential to put its organic molecular solar cells on the roof of hybrid cars such as the Toyota Prius, pending an increase in the voltage of its devices. This could be done either through introducing more stacks or increasing the efficiency of the molecular material used.