Enabling the green transition with high-performing solar cells

Michael Grätzel is pushing the limits of solar energy technology at the École Polytechnique Fédérale de Lausanne, Switzerland, where he is a professor and the director of the Laboratory of Photonics and Interfaces. In 2012, Grätzel won an ERC grant to improve the efficiency of solar cell devices to generate electricity from sunlight. As part of it, he also advanced a new system for generating fuels, such as hydrogen, from sunlight and water.

‘The inspiration for my project actually came from observing nature’, he says. ‘We learned from the way that green leaves harvest sunlight during natural photosynthesis.’ He did not want to replicate all the complexities of the natural system, but rather focused on the primary process during which chlorophyll, the natural dye, generates electric charges from sunlight, so that he could mimic the reaction in an efficient and, ultimately, more reliable way.

New generation of solar power

At the start of ERC funding, Grätzel and his lab were testing two types of solar cell structures comprised of different chemical compounds: the dye-sensitised cell (DSC) and the perovskite solar cell (PSC). In fact, Grätzel had previously invented the DSC in 1991, which would become the ‘mother’ of the PSC in 2009.

Grätzel brought in a mix of Swiss and international researchers to develop the dye molecules and perform the requisite ‘molecular tailoring’ in order to produce a more mature DSC technology. For the PSC, he wanted to advance new compositions and architectures, with the goal of developing solar cell devices that would be highly efficient, stable and low-cost.

‘Without ERC support, we would not have had the freedom or the capacity to do this creative research

Breaking energy conversion records

Thanks in part to Grätzel’s work, the efficiency of the PSC has increased from 3% in 2009 to almost 26% today. Over the last 8-9 years, these breakthroughs in the research have been documented in over 18,000 published papers.

In retrospect, Grätzel emphasises the fact that ERC support came at a critical time – namely in the wake of the 2007-2008 global financial crisis. The support meant that ‘we were much stronger in terms of competitiveness and received advice on how to transition our inventions to practical applications’, he says. The technology that they developed resulted in over 50 patents.

‘Our DSC is now considered the gold standard for ambient light harvesting’, he adds. It can be found in e-readers, headphones, smartphones and other electronic devices marketed as ‘eternal electronics’; solar-powered devices that do not require battery replacements. While the commercial deployment of PSCs is still in its infancy, initial findings suggest it may enable even higher electrical power conversion efficiency rates (in tandem configurations possibly as high as 30%).

A durable electronic future

With the ERC grant, Grätzel sought to contribute to the solar cell technology currently on the market. In addition to this, he was also able to put forth a new generation of molecular solar cell devices that have reached commercial maturity. He is continuing to work on improving these devices and on exploring the complex features of PSCs at the level of fundamental research to prepare for their large-scale deployment in the future.

‘We need more photovoltaic options to stop climate change’, he says. ‘That’s where I think our devices can provide support to the existing photovoltaic technologies.’

Grätzel is not just imaging a new wave of photovoltaic technologies. ‘In my office, I have a photovoltaic glass panel that can contribute electricity for powering my desktop computer. It collects light from all angles!’

Listen to the podcast here: https://soundcloud.com/erc_research/how-the-erc-transformed-science-interview-with-michael-gratzel/s-BJo3ol4WVYj