“We often focus on the bulk properties of materials for energy applications, such as light absorption for solar cells and ion diffusion rates for batteries, but the reality is that interfaces are critical,” says Aron Walsh, Professor of Materials at Imperial College London in the UK. His comments reflect a trend in energy materials research that is becoming increasingly focused at the boundaries, where one material ends and another begins.

According to Walsh the wealth of useful innovations for optimizing energy materials stemming from interface studies owes more to what is not known about these systems than what is. Identifying unexpected physical behaviour at the junction between compounds can provide insights into what might enhance or restrict the performance of a device. In the first issue of of Journal of Physics: Energy researchers starting out in efforts to model these systems can benefit from a technical note by Walsh and colleagues at Imperial College London, the Rutherford Appleton Laboratory in the UK, and Yonsei University in South Korea.

“The technical note is a quick-start guide aimed for new researchers, while those established in the field may find some useful tricks or references,” says Walsh. “We don’t cover the deep challenges such as changes in structure, charge, and stoichiometry at junctions, which are the subjects of on-going investigations and model development. We illustrate how modern atomic and electronic structure techniques can provide valuable insights into the nature of materials interfaces at the atomic scale.”

Tinkering limitations

While it is possible to tinker with parameters here and there and luck out with fixes without really understanding why or how they work (an uncanny knack some people have that still impresses me) as Editor in Chief of Journal of Physics: Energy John Irvine also emphasizes, efforts to better understand the interfaces in new technologies are important for the field to progress. “For a lot of big devices, the important technology is actually at the nanoscale and the interfaces,” he says in a recent interview. “Take something like activation, where a physical or chemical process is triggered: If you engineer at the nanoscale you can actually improve performance by working on the interfaces between, say, the electrode and electrolyte. But you have to understand what’s going on at the nanoscale before you can apply that on a system scale.”

This kind of technical note is a relatively unusual journal article type. Walsh – a University Research Fellow of the Royal Society who in the past few years has been awarded the EU-40 prize from the European Materials Research Society, the Chemistry Society Reviews Emerging Investigator Lectureship for his work on the theory of next-generation materials for solar energy conversion, including halide perovskite photovoltaics, and the Philip Leverhulme prize in Chemistry – tells Physics World that the motivation for the technical note came from the encouraging track record in this field. “As materials modelling is becoming increasingly predictive, there are many researchers entering the field that want to apply the latest tools to energy materials and processes,” says Walsh. “My aim is to have a series of notes that will aid new researchers to get started by providing key references and technical workflows.”

Find the technical note in full at the Journal of Physics: Energy