Energy Research Outlook. What to Look for in 2018 he first issue of ACS Energy Letters was published just 18 months ago. Since then we have published a large number of research articles reporting new advances in energy materials, solar cells, solar fuels, electrochemical energy storage, supercapacitors, display devices, electrocatalysis, photocatalysis, plasmonics, along with theory and modeling. In addition to research articles, Perspectives, and Reviews, we have published Viewpoints and Energy Focus articles as part of the editorial matter to provide a platform for community-wide discussions. We have also jointly published with our sister journals Virtual Issues on lead-free perovskite solar cells,1 perovskite nanocrystals,2 and redox flow batteries.3 As a part of our first anniversary celebration, we introduced the Energy Express feature to facilitate rapid communication of major breakthroughs in research. All these efforts have made ACS Energy Letters one of the premier journals in the energy research field in a very short time. The impact of published articles can be seen by the large number of downloads and citations by our readers. According to Clarivate Analytics (Web of Science Core Collection as of December 31, 2017), 173 research articles published in 2016 have received 1966 citations, thus projecting a maiden impact factor in double digits. Energy research in the new millennium has seen a great amount of diversity with the exploration of innovative nanomaterials and their hybrid assemblies for energy conversion and storage. Advances in time-resolved spectroscopy, surface science, imaging techniques, and various in situ and operando characterization techniques are providing new insights into energy conversion and storage processes. The enthusiasm of researchers worldwide to tackle major hurdles in energy conversion and storage has made this field one of the outstanding frontiers of modern science. Both renewable energy generation and storage were popular topics of 2017. The New Year is expected to bring more excitement in terms of exploration of new materials for photovoltaics, catalysis/ electrocatalysis/photocatalysis, battery electrodes and electrolytes, and energy-efficient displays. The obvious question is what are some specif ic topics to look for in 2018? On the basis of our own research experiences, we have compiled a few potential opportunities, which in our opinion have the potential for important scientific advances (Figure 1). Energy Materials. The quest for new semiconductor materials with photoactivity in the visible and near-infrared will continue. Metal halide perovskite materials will continue to be a hot topic with the ability to tune the 0D/2D/3D morphology through compositional variation and ligand substitution, including mixing perovskites of various dimensionalities to achieve specifically tailored properties not presented by a single material. Perovskite quantum dots are likely to lead the studies involving photodynamic and optoelectronic properties.2 Unraveling the mysteries of photoinduced processes in these materials remains a challenge. Some of these topics include ion
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© 2018 American Chemical Society
Figure 1. Energy research outlook for 2018.
and defect migration, photoinduced phase segregation, nature of defects and trap states, polaron, potential hot carrier transport, surface and interface (photo)chemistry, and chemical stability. The quest for nonprecious electrocatalysts for energy conversion and storage will continue to drive the exploration of new nanomaterials. Electrochemical Energy Conversion and Energy Storage. As a new research area in fuel cells, the anion exchange membrane fuel cells (AEMFC) will continue to be an important topic. With ever-increasing global demand for electric vehicles, development of advanced Ni-rich NCM-based cathode families with improved energy density, lifetime, and safety will accelerate in the coming year. To enhance the energy density and safety of the state-of-the-art lithium-ion batteries, we will see efforts to deploy all-solid-state lithium-metal batteries in devices. Redox flow batteries (RFBs) are promising for gridscale energy storage as several MW scale RFBs have recently been deployed commercially. New RFB chemistry beyond the commercially proven vanadium flow batteries that have even higher energy storage density, lower cost, and excellent cycling performance will accelerate their adoption and deployments. In the field of supercapacitors, investigation of electrode materials like metal sulfide and metal hydroxide will continue to be a main research stream. Solar Cells. The dominance of perovskite solar cell (PSC) research over dye-sensitized solar cells and organic photovoltaics (OPV) has resulted in a new research wave. Although the current record power conversion efficiency (PCE) of PSCs is reaching close to 23%,4 new efforts with multijunction tandem solar cells can boost the PCE greater than that of single-junction solar cells5 (see, for example, http://pubs.acs. org/doi/10.1021/acsenergylett.7b01134). A record PCE of 13.4% with CsPbI3 nanocrystal arrays6 has further energized the research community to explore new opportunities to develop Published: January 12, 2018 261
DOI: 10.1021/acsenergylett.7b01187 ACS Energy Lett. 2018, 3, 261−263
Editorial
Cite This: ACS Energy Lett. 2018, 3, 261−263
ACS Energy Letters
Editorial
into multiscale models to achieve a realistic simulation of device or macroscopic parameters. Theory and modeling studies in ACS Energy Letters should have a strong connection to energy applications, with methodological advances being considered if they enable us to effectively solve an energy-related problem. Computational prediction and design of new materials are also interesting if related to potentially feasible materials. It is difficult to predict what will be the next major breakthrough in science. There are always surprises in any discipline leading to a major leap. The above-mentioned topics should be regarded as possible areas where opportunities exist to make important contributions. We would like to remind our authors to clearly identify the new developments made in their work along with the scientific advances when submitting their manuscripts for publication in ACS Energy Letters. Authors should avoid unnecessary hype and avoid phrases such as “highly efficient” or “novel materials” in their title and discussion of the paper. Also, they should pay attention to figures and graphics for accurate presentation of the data and analysis. We take this opportunity to thank all our authors, reviewers, and readers for their support during our early years and for making ACS Energy Letters a leading journal in the discipline. We look forward to publishing your exciting new advances in energy research with speed and providing the best exposure of published papers in the community. Wishing all our authors, readers, and reviewers a happy and productive new year.
stabilized perovskite quantum dot solar cells. Efforts are also needed in the areas of developing lead-free perovskites for solar cell applications and improving device stability.1 The perovskite solar cell field is also evolving toward optimizing large-area deposition and achieving stable devices, which are critically important for this technology to become mature and be deployed in the market.7 Advances in OPV can be anticipated in the development of ternary and tandem devices with new donor small molecule and polymer materials and nonfullerene acceptor materials with a record PCE in OPV devices >13%. Solar Fuels. In natural photosynthesis, a Z-scheme, which couples multiple single-photon events with series redox processes, enables water oxidation and drives “fuel” (sugar) generation. Effective adaptation of this scheme is important for rational design and development of new photocatalysts and electrocatalysts for water splitting and CO2 reduction. Opportunities exist in the solar energy driven selective catalytic transformation of CO2 to fuels, nitrogen to ammonia, and biomass-derived organic molecules. New approaches are needed to employ photosynthetic proteins as platforms to capture solar photons and facilitate multiple redox reactions for hydrogen generation from water and organic molecule generation from CO2. In the studies of new (nano)materials as photocatalysts or electrocatalysts, establishing their long-term stability in their respective operation conditions and avoidance of the sacrificial electron donors in photocatalytic reactions are some of the most basic requirements to make a meaningful contribution to the field. Meaningful integration of theory with experiments and careful mechanistic studies to identify the catalytic active sites would help the field to go beyond the “trial-and-error” or “cook-and-look” exercises in the initial “gold rush” and lead to a more systematic, rational, and sustainable development process. LED and Display Devices. After three decades of research and development, organic light-emitting diodes (OLED) have achieved great commercial success in the display market to the point that you might well be reading this Editorial on an OLED display device right now. Quantum dot-based displays are also entering commercial deployments. Besides the continued developments in these more “traditional” materials for LEDs, metal halide perovskite materials, especially nanocrystals and nanostructures of halide perovskites, have shown promise for LED and display applications. The challenges facing halide perovskite materials for LED device technology are somewhat similar, but not identical, to those related to perovskite solar cells, such as photophysics related to efficient radiative carrier recombination, LED device performance, materials and device stability due to ion migration and moisture and chemical stability, and development of new lead-free perovskite or perovskite-like light emitters. There will likely be more exciting research activities ahead in this very active area. Theory and Computational Modeling. As in many other fields, theory and computational modeling have had a great impact in the broad energy field. Several intriguing optoelectronic properties of perovskites are still to be revealed, and combined modeling and experimental studies are definitely going to contribute in this direction. Similarly, in the study of catalytic processes, a combination of experimental and modeling data often helps to reveal the details of intricate reaction mechanisms. Modeling has also had an impact in the battery field by predicting new materials and allowing the characterization of reactions at electrodes. The information obtained by electronic structure and atomistic modeling studies can be fed
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RELATED READINGS (1) Kamat, P. V.; Bisquert, J.; Buriak, J. Lead-Free Perovskite Solar Cells. ACS Energy Lett. 2017, 2, 904−905. DOI: 10.1021/ acsenergylett.7b00246. (2) Buriak, J. M.; Kamat, P. V.; Schanze, K. S.; Alivisatos, A. P.; Murphy, C. J.; Schatz, G. C.; Scholes, G. D.; Stang, P. J.; Weiss, P. S. Virtual Issue on Metal-Halide Perovskite NanocrystalsA Bright Future for Optoelectronics. Chem. Mater. 2017. 29, 8915. DOI: 10.1021/acs.chemmater.7b04336. (3) Kamat, P. V.; Schanze, K. S.; Buriak, J. M. Redox Flow Batteries. ACS Energy Lett. 2017, 2, 1368−1369. DOI: 10.1021/ acsenergylett.7b00361. (4) NREL Photovoltaic Research. Best Research-Cell Efficiencies. https://www.nrel.gov/pv/assets/images/ efficiency-chart.png (accessed Dec 10, 2017). (5) Kamat, P. V. Hybrid Perovskites for Multijunction Tandem Solar Cells and Solar Fuels. A Virtual Issue. ACS Energy Lett. 2018, 3, 28−29. DOI: 10.1021/acsenergylett.7b01134. (6) Sanehira, E. M.; Marshall, A. R.; Christians, J. A.; Harvey, S. P.; Ciesielski, P. N.; Wheeler, L. M.; Schulz, P.; Lin, L. Y.; Beard, M. C.; Luther, J. M. Enhanced Mobility CsPbI3 Quantum Dot Arrays for Record-Efficiency, High-Voltage Photovoltaic Cells. Sci. Adv. 2017, 3, eaao4204. DOI: 10.1126/sciadv.aao4204 (7) Berry, J. J.; van de Lagemaat, J.; Al-Jassim, M. M.; Kurtz, S.; Yan, Y.; Zhu, K. Perovskite Photovoltaics: The Path to a Printable Terawatt-Scale Technology. ACS Energy Lett. 2017, 2, 2540−2544. DOI: 10.1021/acsenergylett.7b00964. Lin Chen, Senior Editor Northwestern University, Evanston, Illinois, United States Argonne National Laboratory, Lemont, Illinois, United States 262
DOI: 10.1021/acsenergylett.7b01187 ACS Energy Lett. 2018, 3, 261−263
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Editorial
Filippo De Angelis, Senior Editor Istituto di Scienze e Tecnologie Molecolari del CNR (CNR-ISTM), Perugia, Italy
Song Jin, Senior Editor
University of Wisconsin, Madison, Wisconsin United States
Yang-Kook Sun, Senior Editor
Hanyang University, Seoul, Republic of Korea
Prashant V. Kamat, Editor-in-Chief
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University of Notre Dame, Notre Dame, Indiana, United States
AUTHOR INFORMATION
ORCID
Lin Chen: 0000-0002-8450-6687 Filippo De Angelis: 0000-0003-3833-1975 Song Jin: 0000-0001-8693-7010 Yang-Kook Sun: 0000-0002-0117-0170 Prashant V. Kamat: 0000-0002-2465-6819 Notes
Views expressed in this editorial are those of the authors and not necessarily the views of the ACS.
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DOI: 10.1021/acsenergylett.7b01187 ACS Energy Lett. 2018, 3, 261−263
