The design and control of materials properties, often at the nanoscale, are the foundation of many new strategies for energy generation, storage, and efficiency. Scanning probe microscopy (SPM) has evolved into a very large toolbox for the characterization of properties spanning size scales from hundreds of microns to nanometers. Recent advances in SPM involve properties and size scales of precise relevance to energy-related materials, as presented in this issue. These advances are put into the general context of energy research, and the general principles are summarized.

Scanning probe microscopy (SPM) has made significant contributions to our understanding of the sub-processes underlying photovoltaic action. These techniques allow local investigation of the electrical and optical properties of a material. Spatially resolved measurements of surface photovoltage and photocurrent have been particularly useful in understanding charge generation and separation. In thin-film inorganic solar cells, for example, Kelvin probe force microscopy (KPFM) has revealed that charge separation does not occur at a heterojunction as expected, but instead occurs at a homojunction buried ∼50 nm within the absorbing layer. In organic photovoltaics, submicron maps of photocurrent have contributed to the understanding of the interplay between processing conditions, blend morphology, and device performance. Such functional imaging distinguishes SPM from complementary structural characterization techniques. Our goal in this article is to provide the materials science community with an appreciation for the capabilities, considerations, and limitations associated with SPM studies of solar cell materials and devices. Highlighted techniques include scanning tunneling microscopy, photoconductive atomic force microscopy, near-field scanning optical microscopy, KPFM, and time-resolved electric force microscopy.

Atomistic and nanometer scale mechanisms of electrochemical reactions and ionic flows in solids in the nanometer–micron range persist as terra incognito in modern science. While structural and electronic phenomena are now accessible to electron and scanning probe microscopy (SPM) techniques, probing nanoscale electrochemistry requires the capability to probe local ionic currents. Here, we discuss principles and applications of electrochemical strain microscopy (ESM), a technique based on probing minute deformations induced by electric bias applied to an SPM tip. ESM imaging and spectroscopy are illustrated for several energy storage and conversion materials. We further argue that down-scaling of physical device structures based on oxides necessitates ionic and electrochemical effects to be taken into account. Future pathways for ESM development are discussed.

Atomic force microscopy (AFM)-based impedance spectroscopy provides localized impedance information of materials and interfaces at the nanoscale by utilizing the conductive AFM tip as a moving electrode to detect current response as a function of time and frequency under controlled environments. This capability enables AFM-based nanoscale impedance measurements to play a unique role in enhancing our understanding of many electronic and electrochemical devices. This article introduces the central concepts of AFM-based impedance measurement and reviews recent examples applying this technique to a variety of functional materials systems, in particular focusing on fuel cells, lithium-ion batteries, photoactive biomembranes, as well as other application examples.

High resolution electrochemical imaging methods provide opportunities to study localized phenomena on electrode surfaces. Here, we review recent advances in scanning electrochemical microscopy (SECM) to study materials involved in (electrocatalytic) energy-related applications. In particular, we discuss SECM as a powerful screening technique and also advances in novel techniques based on micro- and nanopipets, such as the scanning micropipet contact method and scanning electrochemical cell microscopy and their use in energy-related research.

Scanning tunneling microscopy (STM) has revolutionized the fields of heterogeneous catalysis and environmental sciences by providing unique insights into the atomic-scale structure of model catalysts. For the first time, STM has revealed the structure of active sites, including steps, kinks, and special atomic geometries in compounds. It has provided images of atomic scale dynamic processes, including diffusion and reactions. STM can operate in environments of gases and liquids, as found in real life and in industrial processes. We illustrate these unique capabilities with examples and how the information obtained can lead to industrially relevant information and help the design of new catalysts.

Research in functional materials is frequently driven by a desire to make informed choices in the quest for better, more effective materials. A great deal of recent attention has been focused on the modalities of how such informed choices can themselves be made in a better, more effective manner. The examples presented here examine some of these modalities, emphasizing the nexus between new synthesis, computational design and analysis, growth in high purity forms, and finally, end-use in terms of either application or of significant property measurement. The illustrations, many drawn from the recent literature, commence with the role that theory has played, both in property prediction and concomitant materials selection, in the areas of multiferroics and topological insulators. The importance of materials quality is emphasized, using examples from observation of the fractional Quantum Hall Effect, where new science has emerged as a result of improved materials. In the area of organic electronics, prospects for advancing the field are suggested, as are future directions in nanoscience. While the examples chosen here point to developments that require a highly collaborative “systems” approach to materials, the role that serendipity plays is not ignored.