Suchergebnisse

Lead halide perovskites have caused a paradigm shift in state-of-the-art photovoltaic technology half a decade ago and have gained tremendous momentum ever since. Given their seemingly imminent commercialization, rigorous scrutiny regarding their potential environmental impact is becoming increasingly relevant. In light of the current need for sustainable energy resources, several start-up and spin-off companies have been established, initially promising modules on the market by the end of 2017. On the downside, lead representing approximately one third by weight of the absorber layer in such photovoltaic devices is enough reason to become wary about the potential environmental impact of their large-scale implementation. Whilst many have wondered where the acceptable boundaries lie regarding lead consumption, it remains a focal point in many discussions, as it seems almost unattainable to ban lead usage from our society. Currently listed as one of the ten chemicals of major health concern by the World Health Organization, the magnitude of misgivings expands even more as recent studies also demonstrate promising applications of lead halide perovskites in light emitting diodes, lasers, batteries, and photodetectors. Hence, there is no doubt that a discussion should be commenced on how to assess and handle the impact of lead in a new technology of such high potential. By reflecting on the historical experience gained from anthropogenic lead poisoning that is still shaping our legislatorial systems at present-day, this work investigates and carefully scrutinizes current legislation that governs the exploitation of lead halide perovskites in optoelectronic applications. Analyzing the repetitive pattern of historical lead consumption, focus is extended on creating awareness and caution toward lead halide perovskite commercialization while concurrently pointing out considerations and ambiguity in policies and regulations. Ultimately, this work aims to initialize a discussion on "if" and "how" this burgeoning class of materials can enter the consumer market. ; A.B. is a Ph.D. fellow of the Research Foundation Flanders (FWO). B.C. is a postdoctoral fellow of FWO. We thank Dirk Weiss and Andreas Wade for the fruitful discussions.

The power conversion efficiency of halide perovskite solar cells is heavily dependent on the perovskite layer being sufficiently smooth and pinhole-free. It has been shown that these features can be obtained even when starting out from rough and discontinuous perovskite film by briefly exposing the film to methylamine (MA) vapor. The exact underlying physical mechanisms of this phenomenon are, however, still unclear. By investigating smooth, MA treated films based on very rough and discontinuous reference films of methylammonium triiode (MAPbI3) and considering their morphology, crystalline features, local conductive properties, and charge carrier lifetime, we unraveled the relation between their characteristic physical qualities and their performance in corresponding solar cells. We discovered that the extensive improvement in photovoltaic performance upon MA treatment is a consequence of the induced morphological enhancement of the perovskite layer together with improved electron injection into TiO2, which in fact compensates for an otherwise compromised bulk electronic quality simultaneously caused by the MA treatment. ; This work was financially supported by BOF (Hasselt University) and the Research Fund Flanders (FWO). B.C. is a postdoctoral research fellow of the FWO. A.B. is financially supported by FWO and Imec. J.V. and N.G. acknowledge funding from GOA project "Solarpaint" of the University of Antwerp and FWO project G.0044.13N "Charge ordering". The Qu-Ant-EM microscope used for this study was partly funded by the Hercules fund from the Flemish Government. The authors thank Tim Vangerven for Urbach energy determination and Johnny Baccus and Jan Mertens for technical support.

A robust and expedient gas quenching method is developed for the solution deposition of hybrid perovskite thin films. The method offers a reliable standard practice for the fabrication of a non-exhaustive variety of perovskites exhibiting excellent film morphology and commensurate high performance in both regular and inverted structured solar cell architectures. ; A.B. and M.T.K. contributed equally to this work. This work was financially supported by BOF (Hasselt University) and the Research Fund Flanders (FWO). B.C. is a postdoctoral research fellow of the FWO. A.B. was financially supported by Imec and FWO (grant V4.667.15N). M.T.K. acknowledges funding from the EPSRC project EP/M024881/1 "Organic-inorganic Perovskite Hybrid Tandem Solar Cells". S.B. is a VINNMER fellow and Marie Sklodowska-Curie fellow. J.V. and N.G. acknowledge funding from GOA project "Solarpaint" of the University of Antwerp and FWO project G.0044.13N "Charge ordering". The Qu-Ant-EM microscope used for this study was partly funded by the Hercules fund from the Flemish Government. N.G. acknowledges funding from the European Research Council under the 7th Framework Program (FP7), ERC Starting Grant 278510 VORTEX. The authors thank Johnny Baccus and Jan Mertens for technical support.

We demonstrate four-and two-terminal perovskite-perovskite tandem solar cells with ideally matched band gaps. We develop an infrared-absorbing 1.2-electron volt band-gap perovskite, FA(0.75)Cs(0.25)Sn(0.5)Pb(0.5)I(3), that can deliver 14.8% efficiency. By combining this material with a wider-band gap FA(0.83)Cs(0.17)Pb(I0.5Br0.5)(3) material, we achieve monolithic two-terminal tandem efficiencies of 17.0% with > 1.65-volt open-circuit voltage. We also make mechanically stacked four-terminal tandem cells and obtain 20.3% efficiency. Notably, we find that our infrared-absorbing perovskite cells exhibit excellent thermal and atmospheric stability, not previously achieved for Sn-based perovskites. This device architecture and materials set will enable "all-perovskite" thin-film solar cells to reach the highest efficiencies in the long term at the lowest costs. ; We thank M. T. Horantner for performing the Shockley-Queisser calculation. The research leading to these results has received funding from the Graphene Flagship (Horizon 2020 grant no. 696656 - GrapheneCore1), the Leverhulme Trust (grant RL-2012-001), the UK Engineering and Physical Sciences Research Council (grant EP/J009857/1 and EP/M020517/1), and the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement nos. 239578 (ALIGN) and 604032 (MESO). T.L. is funded by a Marie Sklodowska Curie International Fellowship under grant agreement H2O2IF-GA-2015-659225. A.B. is financed by IMEC (Leuven) in the framework of a joint Ph.D. program with Hasselt University. B.C. is a postdoctoral research fellow of the Research Fund Flanders (FWO). We also acknowledge the U.S. Office of Naval Research for support. We acknowledge the use of the University of Oxford Advanced Research Computing (ARC) facility (http://dx.doi.org/10.5281/zenodo.22558) and the ARCHER UK National Super-computing Service under the "AMSEC" Leadership project. We thank the Global Climate and Energy Project (GCEP) at Stanford University. All data pertaining to the conclusions of this work can be found in the main paper and the supplementary materials.