While electronic displays have always been the most high profile application for P-OLED technology, there is also the possibility of using the technology 'in reverse', i.e. to convert light into electricity.

Devices which convert light into electricity are called photovoltaic (PV) devices, and are at the heart of solar cells and light detectors. CDT has demonstrated photvoltaic devices using its polymer semiconductor know-how and experience, and has filed several patents in the area.

Digital clocks powered by CDT's
polymer solar cells




Photovoltaic Devices

Polymer PV cells may have an identical structure to polymer displays, and use very similar polymer materials and processing.

The active polymer layer is sandwiched between two conducting electrodes. One of the electrodes is transparent to let the light in or out depending on the application. A conducting polymer layer, called PEDOT, is sometimes used to flatten the transparent anode and help inject / carry positive charges in or out of the device.

Schematic structure of a polymer PV cell (left) and a P-OLED display (right)

Light is absorbed in the polymer layers and creates a pair of negative and positive electric charges; we call these 'electrons' and 'holes'. These charges are collected by the electrodes, forming an electric current, which can be used to drive an electronic device.


The future of polymer solar cells

 

Polymer solar cells have a huge range of potential applications.  Low cost, flexible cells could be used where current expensive technologies are uneconomic.  Look out for disposable solar powered displays on packaging in the future.  Mobile phones, laptop computers and the information appliances of the future may all have solar cells to top up the batteries, and a flexible solar cell can be integrated into the packaging or case. 

Tents made from large area, flexible solar panels could be used by aid agencies to power vaccine fridges or other vital medical equipment.  Light weight, roll-up power sources would also be ideal for people requiring electricity in remote locations, such as field researchers, mountaineers, sailors and military personnel, not to mention the potential in developing nations.

As well as solar cells, polymer PV devices can also be used to make light detectors, with the same advantages of low cost and large area manufacture. This would enable new applications, such as disposable medical image sensors to be made, using sensitive light detection technology in a portable and cheap package.