Using quantum coupled states to improve solar cell efficiency

Today, almost all solar cells deployed on our roofs and at solar farms are made from silicon. However, these cells only use a fraction of their incident sunlight efficiently. Whilst most of the energy in the ‘red’ part of the solar spectrum is turned into electricity, about 60 to 80 percent of the yellow, green and blue parts of the spectrum is lost as heat.

These issues can be overcome by stacking 3 to 4 solar cells that are tuned to different colours of light on top of one another, with each cell harvesting different parts of the solar spectrum more efficiently. However, this comes at a high price. We therefore need simpler and more cost-effective ways to recover this otherwise lost energy and turn it into electricity.

A curious feature in some materials is that when a single photon of high energy light is absorbed, two or more excited states at lower energy are created. This process is called multiple exciton generation (MEG). A team lead by Dr David Jones has been developing new organic semiconductor materials that exploit this property in order to develop high efficiency, lower cost solar cells.

Dr. Jones’ team has shown that we can potentially double the power output of a solar cell via absorbed yellow, green or blue light, increasing its theoretical efficiency from about 32% to 44%. This means that a 20% reduction in the cell’s cost per unit of delivered power is prospective.

Further progress is dependent on the development of new materials that enhance the efficiency of the MEG process. This, in turn, requires researchers to understand and exploit fundamental quantum mechanical properties of organic semiconductor materials.

In support of these efforts, Dr Jones has recently received support from the Australian Renewable Energy Agency ARENA to examine a class of materials that improve silicon solar cell efficiency in this way.

"The ARENA funding will allow us to bring together three key groups to demonstrate that we can exploit the MEG process to enhance solar cell efficiency. This is not just a laboratory curiosity.” said Dr Jones.

"In addition, these new materials can be printed onto silicon solar cells, offering a potentially low-cost method to enhance silicon solar cell efficiency and deliver a significant reduction in costs."

This work will be completed in collaboration with the University of Queensland and the Australian National University.

You can read more about the project and the funding on the ARENA website.