Luminescent solar concentrators to complement traditional solar harvesting technology

A team of researchers at the ARC Centre of Excellence in Exciton Science is creating materials that could transform windows and walls into solar cells, raising the possibility of self-powered buildings.

Dr Wallace Wong and Professor Ken Ghiggino at The University of Melbourne and Professor Tim Schmidt at the University of New South Wales are working to make better luminescent solar concentrators (LSCs). These light-harvesting devices are designed to capture energy from light in cities and other places without bright direct sunlight.

LSCs are made from sheets of semi-transparent material containing highly luminescent compounds that absorb sunlight and then re-emit it at longer wavelengths. This light is then trapped and guided to the thin edges of the material, where photovoltaic cells are waiting to absorb it and generate electricity.

LSCs have been under development for several decades, but they are not yet efficient enough to be commercially viable. Energy can be lost in the form of waste heat while the trapped light is bouncing around inside the device, reducing the power output per unit area.

Dr Wong is an expert in the synthesis of functional organic materials, while Professors Ghiggino and Schmidt are experts in spectroscopic analysis of materials. With their research teams and in collaboration with other Centre researchers, they are designing and synthesising new luminescent compounds, such as organic dyes and quantum dots, that can efficiently harvest light over a large surface area.

Such materials will hopefully lead to more stable, higher-performance LSC devices.

“LSC technology is simple in concept, but requires a multidisciplinary approach to overcome existing limitations and make useful devices,” says Professor Ghiggino.

“The challenges involve understanding the fundamental science and applying expertise in theoretical modelling, chemical synthesis, photochemistry, optics and device engineering.”

The researchers say that this light-harvesting technology is particularly exciting because it can capture diffuse light, and in urban environments and low light conditions, LSCs can outperform traditional solar cells.

LSCs are not in direct competition with rooftop silicon solar cells however, and it will be a little longer before the true potential of LSCs can be realised. Their components presently have a limited lifetime under full sun, so applications are geared more towards indoor devices.

“In the near future, LSCs can be used to help extend the battery life of small consumer electronics such as mobile phones,” says Dr Wong. “With better performance and stability, building integrated applications—such as light-harvesting walls and windows—is possible.”

This means that with LSCs, the glass that allows sunlight into homes and offices could also generate the electricity needed to run them.

“Potentially any surface exposed to light can become a collector for electricity generation,” says Professor Ghiggino, adding that ‘zero net energy’ buildings might one day be a possibility, in which the building captures as much energy as it uses.

Recently, Dr Wong and Professor Ghiggino demonstrated a large-area LSC fabricated using printing methods with state-of-the-art performance. The steady improvements made at the Centre of Excellence in Exciton Science are important stepping stones to creating the energy efficient cities of the future.

Image: A high performance luminescent concentrator developed by ARC Centre of Excellence in Exciton Science researchers. Credit: ARC Centre of Excellence in Exciton Science.