@article{KegelmannWolffAwinoetal.2017, author = {Kegelmann, Lukas and Wolff, Christian Michael and Awino, Celline and Lang, Felix and Unger, Eva L. and Korte, Lars and Dittrich, Thomas and Neher, Dieter and Rech, Bernd and Albrecht, Steve}, title = {It Takes Two to Tango-Double-Layer Selective Contacts in Perovskite Solar Cells for Improved Device Performance and Reduced Hysteresis}, series = {ACS applied materials \& interfaces}, volume = {9}, journal = {ACS applied materials \& interfaces}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/acsami.7b00900}, pages = {17246 -- 17256}, year = {2017}, abstract = {Solar cells made from inorganic organic perovskites have gradually approached market requirements as their efficiency and stability have improved tremendously in recent years. Planar low-temperature processed perovskite solar cells are advantageous for possible large-scale production but are more prone to exhibiting photocurrent hysteresis, especially in the regular n-i-p structure. Here, a systematic characterization of different electron selective contacts with a variety of chemical and electrical properties in planar n-i-p devices processed below 180 degrees C is presented. The inorganic metal oxides TiO2 and SnO2, the organic fullerene derivatives C-60, PCBM, and ICMA, as well as double-layers with a metal oxide/PCBM structure are used as electron transport materials (ETMs). Perovskite layers deposited atop, the different ETMs with the herein applied fabrication method show a similar morphology according to scanning electron microscopy. Further, surface photovoltage spectroscopy measurements indicate comparable perovskite absorber qualities on all ETMs, except TiO2, which shows a more prominent influence of defect states. Transient photoluminescence studies together with current voltage scans over a broad range of scan speeds reveal faster charge extraction, less pronounced hysteresis effects, and higher efficiencies for devices with fullerene compared to those with metal oxide ETMs. Beyond this, only double-layer ETM structures substantially diminish hysteresis effects for all performed scan speeds and strongly enhance the power conversion efficiency up to a champion stabilized value of 18.0\%. The results indicate reduced recombination losses for a double-layer TiO2/PCBM contact design: First, a reduction of shunt paths through the fullerene to the ITO layer. Second, an improved hole blocking by the wide band gap metal oxide. Third, decreased transport losses due to an energetically more favorable contact, as implied by photoelectron spectroscopy measurements. The herein demonstrated improvements of multilayer selective contacts may serve as a general design guideline for perovskite solar cells.}, language = {en} } @article{CochLamoureuxKnoblauchetal.2018, author = {Coch, Caroline and Lamoureux, Scott F. and Knoblauch, Christian and Eischeid, Isabell and Fritz, Michael and Obu, Jaroslav and Lantuit, Hugues}, title = {Summer rainfall dissolved organic carbon, solute, and sediment fluxes in a small Arctic coastal catchment on Herschel Island (Yukon Territory, Canada)}, series = {Artic science}, volume = {4}, journal = {Artic science}, number = {4}, publisher = {Canadian science publishing}, address = {Ottawa}, issn = {2368-7460}, doi = {10.1139/as-2018-0010}, pages = {750 -- 780}, year = {2018}, abstract = {Coastal ecosystems in the Arctic are affected by climate change. As summer rainfall frequency and intensity are projected to increase in the future, more organic matter, nutrients and sediment could bemobilized and transported into the coastal nearshore zones. However, knowledge of current processes and future changes is limited. We investigated streamflow dynamics and the impacts of summer rainfall on lateral fluxes in a small coastal catchment on Herschel Island in the western Canadian Arctic. For the summer monitoring periods of 2014-2016, mean dissolved organic matter flux over 17 days amounted to 82.7 +/- 30.7 kg km(-2) and mean total dissolved solids flux to 5252 +/- 1224 kg km(-2). Flux of suspended sediment was 7245 kg km(-2) in 2015, and 369 kg km(-2) in 2016. We found that 2.0\% of suspended sediment was composed of particulate organic carbon. Data and hysteresis analysis suggest a limited supply of sediments; their interannual variability is most likely caused by short-lived localized disturbances. In contrast, our results imply that dissolved organic carbon is widely available throughout the catchment and exhibits positive linear relationship with runoff. We hypothesize that increased projected rainfall in the future will result in a similar increase of dissolved organic carbon fluxes.}, language = {en} } @article{AlxatibSauerland2019, author = {Alxatib, Sam and Sauerland, Ulrich}, title = {Vagueness}, series = {The Oxford Handbook of Experimental Semantics and Pragmatics}, journal = {The Oxford Handbook of Experimental Semantics and Pragmatics}, publisher = {Oxford University Press}, address = {Oxford}, doi = {10.1093/oxfordhb/9780198791768.013.24}, pages = {28}, year = {2019}, abstract = {Though vague phenomena have been studied extensively for many decades, it is only in recent years that researchers sought the support of quantitative data. This chapter highlights and discusses the insights that experimental methods brought to the study of vagueness. One area focused on are 'borderline contradictions', that is, sentences like 'She is neither tall nor not tall' that are contradictory when analysed in classical logic, but are actually acceptable as descriptions of borderline cases. The flourishing of theories and experimental studies that borderline contradictions have led to are examined closely. Beyond this illustrative case, an overview of recent studies that concern the classification of types of vagueness, the use of numbers, rounding, number modification, and the general pragmatic status of vagueness is provided.}, language = {en} } @article{MunyaevSmirnovKostinetal.2020, author = {Munyaev, Vyacheslav O. and Smirnov, Lev A. and Kostin, Vasily A. and Osipov, Grigory V. and Pikovskij, Arkadij}, title = {Analytical approach to synchronous states of globally coupled noisy rotators}, series = {New journal of physics : the open-access journal for physics}, volume = {22}, journal = {New journal of physics : the open-access journal for physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/ab6f93}, pages = {14}, year = {2020}, abstract = {We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.}, language = {en} } @article{MunyaevSmirnovKostinetal.2020, author = {Munyaev, Vyacheslav and Smirnov, Lev A. and Kostin, Vasily and Osipov, Grigory V. and Pikovskij, Arkadij}, title = {Analytical approach to synchronous states of globally coupled noisy rotators}, series = {New Journal of Physics}, volume = {22}, journal = {New Journal of Physics}, number = {2}, publisher = {Springer Science}, address = {New York}, pages = {15}, year = {2020}, abstract = {We study populations of globally coupled noisy rotators (oscillators with inertia) allowing a nonequilibrium transition from a desynchronized state to a synchronous one (with the nonvanishing order parameter). The newly developed analytical approaches resulted in solutions describing the synchronous state with constant order parameter for weakly inertial rotators, including the case of zero inertia, when the model is reduced to the Kuramoto model of coupled noise oscillators. These approaches provide also analytical criteria distinguishing supercritical and subcritical transitions to the desynchronized state and indicate the universality of such transitions in rotator ensembles. All the obtained analytical results are confirmed by the numerical ones, both by direct simulations of the large ensembles and by solution of the associated Fokker-Planck equation. We also propose generalizations of the developed approaches for setups where different rotators parameters (natural frequencies, masses, noise intensities, strengths and phase shifts in coupling) are dispersed.}, language = {en} } @article{CookTurowskiHovius2020, author = {Cook, Kristen L. and Turowski, Jens M. and Hovius, Niels}, title = {Width control on event-scale deposition and evacuation of sediment in bedrock-confined channels}, series = {Earth surface processes and landforms : the journal of the British Geomorphological Research Group}, volume = {45}, journal = {Earth surface processes and landforms : the journal of the British Geomorphological Research Group}, number = {14}, publisher = {Wiley}, address = {Hoboken}, issn = {0197-9337}, doi = {10.1002/esp.4993}, pages = {3702 -- 3713}, year = {2020}, abstract = {In mixed bedrock-alluvial rivers, the response of the system to a flood event can be affected by a number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes and upstream, flood sequencing and coarse sediment grain size distribution. However, the impact of along-stream changes in channel width on bedload transport dynamics remains largely unexplored. We combine field data, theory and numerical modelling to address this gap. First, we present observations from the Daan River gorge in western Taiwan, where the river flows through a 1 km long 20-50 m wide bedrock gorge bounded upstream and downstream by wide braidplains. We documented two flood events during which coarse sediment evacuation and redeposition appear to cause changes of up to several metres in channel bed elevation. Motivated by this case study, we examined the relationships between discharge, channel width and bedload transport capacity, and show that for a given slope narrow channels transport bedload more efficiently than wide ones at low discharges, whereas wider channels are more efficient at high discharges. We used the model sedFlow to explore this effect, running a random sequence of floods through a channel with a narrow gorge section bounded upstream and downstream by wider reaches. Channel response to imposed floods is complex, as high and low discharges drive different spatial patterns of erosion and deposition, and the channel may experience both of these regimes during the peak and recession periods of each flood. Our modelling suggests that width differences alone can drive substantial variations in sediment flux and bed response, without the need for variations in sediment supply or mobility. The fluctuations in sediment transport rates that result from width variations can lead to intermittent bed exposure, driving incision in different segments of the channel during different portions of the hydrograph.}, language = {en} } @article{OtterMondalAlrefaietal.2021, author = {Otter, Dirk and Mondal, Suvendu Sekhar and Alrefai, Anas and Kr{\"a}tz, Lorenz and Holdt, Hans-J{\"u}rgen and Bart, Hans-J{\"o}rg}, title = {Characterization of an isostructural MOF series of Imidazolate Frameworks Potsdam by means of sorption experiments with water vapor}, series = {Nanomaterials}, volume = {11}, journal = {Nanomaterials}, number = {6}, publisher = {MDPI}, address = {Basel}, issn = {2079-4991}, doi = {10.3390/nano11061400}, pages = {20}, year = {2021}, abstract = {Sorption measurements of water vapor on an isoreticular series of Imidazolate Frameworks Potsdam (IFP), based on penta-coordinated metal centers with secondary building units (SBUs) connected by multidentate amido-imidate-imidazolate linkers, have been carried out at 303.15 K. The isotherm shapes were analyzed in order to gain insight into material properties and compared to sorption experiments with nitrogen at 77.4 K and carbon dioxide at 273.15 K. Results show that water vapor sorption measurements are strongly influenced by the pore size distribution while having a distinct hysteresis loop between the adsorption and desorption branch in common. Thus, IFP-4 and -8, which solely contain micropores, exhibit H4 (type I) isotherm shapes, while those of IFP-1, -2 and -5, which also contain mesopores, are of H3 (type IV) shape with three inflection points. The choice of the used linker substituents and transition metals employed in the framework has a tremendous effect on the material properties and functionality. The water uptake capacities of the examined IFPs are ranging 0.48 mmol g(-1) (IFP-4) to 6.99 mmol g(-1) (IFP-5) and comparable to those documented for ZIFs. The water vapor stability of IFPs is high, with the exception of IFP-8.}, language = {en} } @article{LeCorreDiekmannPenaCamargoetal.2022, author = {Le Corre, Vincent M. and Diekmann, Jonas and Pe{\~n}a-Camargo, Francisco and Thiesbrummel, Jarla and Tokmoldin, Nurlan and Gutierrez-Partida, Emilio and Peters, Karol Pawel and Perdig{\´o}n-Toro, Lorena and Futscher, Moritz H. and Lang, Felix and Warby, Jonathan and Snaith, Henry J. and Neher, Dieter and Stolterfoht, Martin}, title = {Quantification of efficiency losses due to mobile ions in Perovskite solar cells via fast hysteresis measurements}, series = {Solar RRL}, volume = {6}, journal = {Solar RRL}, number = {4}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {2367-198X}, doi = {10.1002/solr.202100772}, pages = {10}, year = {2022}, abstract = {Perovskite semiconductors differ from most inorganic and organic semiconductors due to the presence of mobile ions in the material. Although the phenomenon is intensively investigated, important questions such as the exact impact of the mobile ions on the steady-state power conversion efficiency (PCE) and stability remain. Herein, a simple method is proposed to estimate the efficiency loss due to mobile ions via "fast-hysteresis" measurements by preventing the perturbation of mobile ions out of their equilibrium position at fast scan speeds (approximate to 1000 V s(-1)). The "ion-free" PCE is between 1\% and 3\% higher than the steady-state PCE, demonstrating the importance of ion-induced losses, even in cells with low levels of hysteresis at typical scan speeds (approximate to 100mv s(-1)). The hysteresis over many orders of magnitude in scan speed provides important information on the effective ion diffusion constant from the peak hysteresis position. The fast-hysteresis measurements are corroborated by transient charge extraction and capacitance measurements and numerical simulations, which confirm the experimental findings and provide important insights into the charge carrier dynamics. The proposed method to quantify PCE losses due to field screening induced by mobile ions clarifies several important experimental observations and opens up a large range of future experiments.}, language = {en} }