In order to prevent catastrophic climate change it has become clear that there is a great need for a wide range of sustainable and renewable energy sources in our energy supply. With more energy reaching the Earth in the form of sunlight per hour than we humans collectively use in a year, solar cells, or photovoltaics, have a massive potential to fill a significant amount of the world’s energy needs with clean energy. Over the past decades, the price of energy from traditional silicon solar cells has decreased by more than a factor of 200, largely due to improvements in silicon processing and an ever-evolving understanding of the microscopic properties underpinning the performance of silicon photovoltaics. Currently, the performance of silicon photovoltaics is nearing the fundamental Shockley-Queisser limit, and it is clear that new photovoltaic materials are needed to further decrease the price of photovoltaic energy.
Hybrid perovskites form an exciting family of novel energy materials with great potential to complement silicon as an important clean energy source for the future. Since their first use in 2009, the performance of solar cells based on perovskites has increased from below 4 % to above 25 % in 2020. This unprecedented rise has largely been driven by improvements in material chemistry, processing methods, and understanding based on macroscopic to microscopic probing methods. One of the main challenges in characterising hybrid organic-inorganic perovskites in general is their highly unstable nature, meaning that they readily dissociate when exposed to a variety of environments, including intense electron irradiation.
In the STEM Group, we use our carefully developed low-dose electron microscope techniques to study these promising PV materials. Our approach enables us to obtain highly detailed information about the properties of hybrid perovskites down to the atomic level, with atomic resolution, not available to any other techniques. Using our world-class microscopes, we image novel perovskite compositions, revealing the microscopic properties that set them apart from most other photovoltaic materials.
Our work involved strong collaborations with Professors Laura Herz, Paolo Radaelli, Henry Snaith, and Michael Johnston in the Physics Department, where our EM characterisations complement the leading efforts in material synthesis and spectroscopy that takes place there.
