Imagine a world where your purse, bag or phone case could charge your electronic devices with the power of the sun. Thanks to Victorian Organic Solar Cell (VICOSC), a massive collaboration between CSIRO, Bosch, BlueScope Steel, Innovia, the University of Melbourne and Monash University that world may soon be a reality. CSIRO’s senior research scientist Dr Fiona Scholes says that semi-transparent thin film solar technologies can replace any plastic surface with a working solar cell. From laptop cases that charge your phone in the sun, to tinted windows on towering skyscrapers powering the grid, the applications for a ubiquitous thin film solar technology are endless.
The trick of course is to find a cheap and reliable means of manufacturing a mass quantity of cells, and VICOSC has found a way to do it—the printing press. Instead of the plastic banknotes that make up the Australian dollar, researchers have modified commercial printers to accept solar inks and effectively print thin flexible photovoltaic sheets. Since they’re still using commercial printers, the manufacturing process is incredibly cost effective and scalable, and VICOSC is already gearing up to expand upon the capabilities of its pilot scale production process.
Solar inks are typically comprised of metal salts suspended in a polymer fullerene blend. The ink may consist of a photoactive layer made up of p-type polymer and an n-type fullerene, a hole transport ink, and can be combined with a cathode and an anode suspended on a substrate. Since the system can be applied in layered coatings, it is possible to use existing ink jet printer technologies to print working solar cells onto plastic substrates.
CSIRO specializes in perovskite solar cells, which derive their name from the ABX3 crystal structures of the photo absorber materials used in this type of cell. The perovskite structure is any material that maintains the same structure as calcium titanium oxide (CaTiO3). The letters A and B denote two cations of significantly differing sizes, and the X refers to the anion that bonds to the cations. In the case of perovskite solar cells, the X is a halogen such as indium, bromine or chlorine.
The chief advantage of using solar inks is their low cost of production. Conventional silicon solar cells must be manufactured in airtight vacuum sealed chambers and dust free rooms which significantly drive up the cost of manufacturing. Since printed solar cells can be manufactured at atmospheric pressure and ambient temperature, not to mention the low cost of commercial ink jet printers, it they are much cheaper to produce. While efficiencies in the range of 2 - 10% may not look like much, the ability to cover large surface areas such as the windows of a skyscraper at very low cost make solar ink technologies a viable renewable energy technology.
Currently VICOSC can print 10 x 10 centimetre flexible solar modules, but soon they will be printing A3 sized panels. The project is funded by the Australian Renewable Energy Agency (ARENA) and the Victoria state government. While they are sticking to plastic for the moment, VICOSC hopes to refine the process to allow them to print solar ink directly onto other surfaces, like rooftops or glass windows. Cheap and printable, these solar panels would be easy to deploy in third world countries offering energy independence and a clean alternative to a much wider span of people than current commercial solar technologies.