Publishing Hybrid/Organic Photovoltaics Papers in ACS Energy Letters
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Considering the number of published papers and their impact in terms of citations, theory and modeling papers are also successfully contributing to our understanding of perovskite solar cells. Advances in Density Functional Theory and the availability of commercial or freely distributed codes, along with the increase of off-the-shelf computer power, have led to the routine calculation of systems composed of several hundred atoms in complex environments, both in their ground and excited states. These conditions have enormously boosted the number of published theory/modeling papers related to HOPV, though their impact to the field is sometimes questionable, some of them representing barely technical benchmarks of slightly different combinations of methods. I have personally read about 20 papers on the same methylammonium lead iodide perovskite stating that “the top of the valence band is composed by iodine, while the bottom of the conduction band is made by lead” and reporting the same (sometimes even wrong) band structure, obtained by slightly different (sometimes even the same) methodological approaches. With this Editorial, we wish to discuss the criteria that we think a manuscript in the broad HOPV field, including perovskites, should satisfy for publication in ACS Energy Letters. As the Letter format requires, a strong prerequisite of a potentially suited ACS Energy Letters paper is the urgency criteria. As Editors, we struggle to ensure a minimal time lapse from submission to publication, pushing Reviewers to adhere to rather stringent timings to submit their reports. This implies a paper will not be considered if it does not completely fulfill the urgency criteria. For “urgent” papers, we mean those reporting significant advances in the field that need to be rapidly communicated, providing clear mechanistic insights or scientific reasons for observing a given property (such as the increase of a solar cell device of any type, or the diminished bimolecular recombination, or the passivation of grain boundaries, etc.). For example, we will be less likely to consider as urgent results that simply compare performances between cellsmy cell works better than the otheror that adding some ingredient (e.g., gold nanoparticles or some surfactant) improves the solar cell performance by some fraction over a standard method or similar. Basic papers addressing important issues of practical relevance, for example, understanding the basic electron/hole dynamics and charge generation mechanisms in HOPV devices and interfaces, or papers presenting new materials with potentially HOPV-relevant optoelectronic properties are also welcome. Theory papers should have some relevance to the practical world, either by providing a direct connection to experimental observables, thus aiding the interpretation of previous and future experiments, or by casting new problems and proposing
ith the swift surge of organohalide metal perovskites as a major player in the arena of emerging photovoltaic technologies, the field of traditional Hybrid/Organic Photovoltaics (HOPV) has been profoundly modified. By traditional HOPV, here we mean dye-sensitized solar cells (DSCs), bulk heterojunction or small-molecule organic solar cells (OSCs), and quantum dot solar cells (QSCs). These technologies dominated publications in basic and applied science journals up to 2012, when the perovskite storm started with the first reports of high-efficiency solid-state perovskite solar cells.1,2 Despite being initially based on a typical DSC architecture,3 perovskite solar cells have outperformed their DSC ancestor in about 2 years from their inception, demonstrating a high efficiency (>22%) in a variety of solid-state device architectures, ranging all the way from a planar to a mesoscopic heterojunction. Since 2012, traditional HOPV technologies have been somehow lying in the shadow of the perovskite giant, mainly due to the efficiency gap between traditional HOPV (topping after 2 decades of research at 11− 14%) and perovskite solar cells. Authors publishing research papers in photovoltaics necessarily have to confront themselves with the efficiency of their devices or, for theory/modeling papers, with the implications of their findings on the efficiency of the related solar cell devices. Efficiency should however not be considered as the only parameter qualifying a research paper in photovoltaics, and in this respect traditional HOPV, with their multiple interfaces and complex environments, represent an optimal playground for basic science. Just consider the amount of scientific discussion devoted to electron injection/recombination in DSCs, or the role of charge-transfer states in OSCs, or quantum confinement and ligand passivation in QSCs. Perovskites have also stimulated several basic questions, mainly related to the outstanding intrinsic materials properties, but the high efficiency of the ensuing devices has somehow hindered a comparable search for a basic understanding of their optoelectronic properties. Also, a relatively limited number of ABX3 perovskite materials based on the combination of A = cesium, methylammonium, formamidinium, B = Pb (or Sn), and X = I, Br, or Cl has mainly driven research toward application in efficient devices. Basically, one can wonder: Why perform basic studies on possibly poorly working materials or devices when one can easily fabricate high-performance devices with small variations in materials choice or device preparation? An additional but not secondary issue to be taken into account in the entire HOPV field is the reproducibility of device data,4,5 with even the NREL chart reporting for perovskites “not stabilized” device efficiencies. Alongside experimental research, theory and modeling had a significant impact in advancing the entire HOPV field and similarly several research groups, including my own, have shifted their research from traditional HOPV to perovskites. © 2016 American Chemical Society
Published: September 9, 2016 646
DOI: 10.1021/acsenergylett.6b00361 ACS Energy Lett. 2016, 1, 646−647
Editorial
http://pubs.acs.org/journal/aelccp
ACS Energy Letters
Editorial
new effects (e.g., dynamic disorder or spin−orbit coupling effects in organohalide perovskites, or hot injection in OSCs, or multiple exciton generation in QCSs) that could motivate their testing in experiments, with the ultimate goal of advancing our knowledge of the HOPV field, thus improving its impact in solar energy production. Technical papers or methodological advances will be considered only if they are clearly motivated by significant advances in the solution of problems of the type mentioned above. Similarly, papers proposing the (highthroughput) computational screening of new solar energy materials will be considered only if a connection to feasible compounds is clearly made. Addition of an electron-rich group to the donor moiety of an organic dye or polymer will raise its HOMO energy; we know it; this is not urgent. Structural modification of a (dye) small molecule or polymer leading to increased radiative lifetime and reducing recombination losses in solar cells devices is likely to be urgent. We hope this discussion, intentionally written in a provocative style, will help authors to meet certain criteria before they can consider submitting a paper to ACS Energy Letters. We very much look forward to receiving your most exciting science in the broad HOPV field.
Filippo De Angelis,* Senior Editor
Computational Laboratory for Hybrid/Organic Photovoltaics (CLHYO), Istituto CNR di Scienze e Tecnologie Molecolari (ISTM-CNR), Via Elce di Sotto 8, 06123 Perugia, Italy CompuNet, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy
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AUTHOR INFORMATION
Corresponding Author
*E-mail: fi
[email protected]. Notes
Views expressed in this editorial are those of the author and not necessarily the views of the ACS.
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REFERENCES
(1) Kim, H.-S.; Lee, C.-R.; Im, J.-H.; Lee, K.-B.; Moehl, T.; Marchioro, A.; Moon, S.-J.; Humphry-Baker, R.; Yum, J.-H.; Moser, J. E.; et al. Lead Iodide Perovskite Sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%. Sci. Rep. 2012, 2, 591. (2) Lee, M. M.; Teuscher, J.; Miyasaka, T.; Murakami, T. N.; Snaith, H. J. Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites. Science 2012, 338, 643−647. (3) Kojima, A.; Teshima, K.; Shirai, Y.; Miyasaka, T. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. J. Am. Chem. Soc. 2009, 131, 6050−6051. (4) Christians, J. A.; Manser, J. S.; Kamat, P. V. Best Practices in Perovskite Solar Cell Efficiency Measurements. Avoiding the Error of Making Bad Cells Look Good. J. Phys. Chem. Lett. 2015, 6, 852−857. (5) Buriak, J. M. Your Research Results Look Compelling, but Are They Reliable? Chem. Mater. 2014, 26, 2211−2213.
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DOI: 10.1021/acsenergylett.6b00361 ACS Energy Lett. 2016, 1, 646−647
