Devices for the generation, storage, and efficient use of energy are critical for the development of new technologies that address the global challenge of a changing climate. As the properties of bulk materials are optimised, the focus is increasingly on enhancing the buried interfaces which are known to be crucial for successful performance. Whilst each technology is evaluating different performance metrics, the common issue of understanding interfacial processes leads to common research questions about how one can explore interfacial processes and study the transport of ions, electrons, and phonons across interfaces. Critically, this means moving away from the study of individual materials to ensembles, adding complexity and in some cases issues with compatibility.

This special issue presents advances in the growth and characterisation of interfaces in energy materials. Encompassing the fields of thermoelectrics, solid-state batteries, solid-oxide fuel cells, and interface electronics, it addresses some of the key issues within these fields. The papers in this issue address from both an experimental and theoretical perspective the importance of interfaces in such applications. The influence of the microstructure on the transport properties is addressed in ideal interfaces prepared under controlled conditions, those formed spontaneously and those developed in more realistic working devices. Strategies for formation and retention of optimised interfaces are also discussed. Each of these contributions addresses different technologies but highlights the vital role that interfaces play in all of these technologies. We hope that by highlighting these technologies in one issue, common themes will emerge and new opportunities for cross-disciplinary collaboration will result, leading to disruptive technology advances.

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