| 1. |
- Anzt, Hartwig, et al.
(author)
-
An environment for sustainable research software in Germany and beyond: current state, open challenges, and call for action
- 2020
-
In: F1000 Research. - : F1000 Research Ltd. - 2046-1402. ; 9
-
Journal article (peer-reviewed)abstract
- Research software has become a central asset in academic research. It optimizes existing and enables new research methods, implements and embeds research knowledge, and constitutes an essential research product in itself. Research software must be sustainable in order to understand, replicate, reproduce, and build upon existing research or conduct new research effectively. In other words, software must be available, discoverable, usable, and adaptable to new needs, both now and in the future. Research software therefore requires an environment that supports sustainability. Hence, a change is needed in the way research software development and maintenance are currently motivated, incentivized, funded, structurally and infrastructurally supported, and legally treated. Failing to do so will threaten the quality and validity of research. In this paper, we identify challenges for research software sustainability in Germany and beyond, in terms of motivation, selection, research software engineering personnel, funding, infrastructure, and legal aspects. Besides researchers, we specifically address political and academic decision-makers to increase awareness of the importance and needs of sustainable research software practices. In particular, we recommend strategies and measures to create an environment for sustainable research software, with the ultimate goal to ensure that software-driven research is valid, reproducible and sustainable, and that software is recognized as a first class citizen in research. This paper is the outcome of two workshops run in Germany in 2019, at deRSE19 - the first International Conference of Research Software Engineers in Germany - and a dedicated DFG-supported follow-up workshop in Berlin.
|
|
| 2. |
- Felix, Roberto, et al.
(author)
-
Photoinduced phase segregation and degradation of perovskites revealed by x-ray photoelectron spectroscopy
- 2019
-
In: 2019 IEEE 46th Photovoltaic Specialists Conference, PVSC 2019. - 0160-8371. - 9781728104942 ; , s. 2362-2367
-
Conference paper (peer-reviewed)abstract
- Pb-based perovskite absorbers with organic (i.e., CH3NH3+) and inorganic (i.e., Cs+) cations and a halide composition of 75% Br and 25% I are investigated with x-ray photoelectron spectroscopy while submitted to environmental stress factors to study their stability. Changes in chemical properties of the absorbers were monitored in ultra-high vacuum and under simulated solar, as well as, x-ray irradiation. Although changes are detected for both types of perovskite absorbers, the organic cation perovskite exhibits a more pronounced tendency to photodegrade.
|
|
| 3. |
- Fenske, Markus, et al.
(author)
-
Improved Electrical Performance of Perovskite Photovoltaic Mini-Modules through Controlled PbI2 Formation Using Nanosecond Laser Pulses for P3 Patterning
- 2021
-
In: Energy Technology. - : Wiley. - 2194-4288 .- 2194-4296. ; 9:4
-
Journal article (peer-reviewed)abstract
- The upscaling of perovskite solar cells to modules requires the patterning of the layer stack in individual cells that are monolithically interconnected in series. This interconnection scheme is composed of three lines, P1–P3, which are scribed using a pulsed laser beam. The P3 scribe is intended to isolate the back contact layer of neighboring cells, but is often affected by undesired effects such as back contact delamination, flaking, and poor electrical isolation. Herein, the influence of the laser pulse duration on the electrical and compositional properties of P3 scribe lines is investigated. The results show that both nanosecond and picosecond laser pulses are suitable for P3 patterning, with the nanosecond pulses leading to a higher open circuit voltage, a higher fill factor, and a higher power conversion efficiency. It is found that the longer pulse duration resultes in a larger amount of PbI2 formed within the P3 line and a thin Br-rich interfacial layer which both effectively passivate defects at the scribe line edges and block charge carrier in its vicinity. Thus, nanosecond laser pulses are preferable for P3 patterning as they promote the formation of beneficial chemical phases, resulting in an improved photovoltaic performance.
|
|
| 4. |
- Hermerschmidt, Felix, et al.
(author)
-
Finally, inkjet-printed metal halide perovskite LEDs-utilizing seed crystal templating of salty PEDOT:PSS
- 2020
-
In: Materials Horizons. - : Royal Society of Chemistry (RSC). - 2051-6347 .- 2051-6355. ; 7:7, s. 1773-1781
-
Journal article (peer-reviewed)abstract
- Solution-processable metal halide perovskites are increasingly implemented in perovskite-based light-emitting diodes (PeLEDs). Especially green PeLEDs based on methylammonium lead bromide (MAPbBr3) composites exhibit impressive optoelectronic properties, while allowing processing by low-cost and upscalable printing methods. In this study, we have investigated the influence of potassium chloride (KCl) blended into the common hole injection material poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) to boost PeLED device performance. The inclusion of KCl firstly results in a change in morphology of the PEDOT:PSS layer, which then acts as a template during deposition of the perovskite layer. A MAPbBr3:polyethylene glycol (PEG) composite was used, which does not require the deposition of an anti-solvent droplet to induce preferential perovskite crystallization and is therefore suitable for spin coating and scalable inkjet printing processes. PeLEDs utilizing the KCl induced templating effect on a planar PEDOT:PSS/MAPbBr3:PEG architecture show improved performance, predominantly due to improved crystallization. PeLEDs incorporating spin-coated perovskite layers yield a 40-fold increase in luminance (8000 cd m-2) while the turn-on voltage decreases to 2.5 V. KCl-modified PEDOT:PSS contact layers enabled the realization of inkjet-printed PeLEDs with luminance increased by a factor of 20 at a maximum of 4000 cd m-2 and a turn-on voltage of 2.5 V. This work paves the way for inkjet-printed perovskite light-emitting devices for a wide variety of low-cost and customizable applications. This journal is
|
|
| 5. |
- Kegelmann, Lukas, et al.
(author)
-
It Takes Two to Tango - Double-Layer Selective Contacts in Perovskite Solar Cells for Improved Device Performance and Reduced Hysteresis
- 2017
-
In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 9:20, s. 17245-17255
-
Journal article (peer-reviewed)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 °C is presented. The inorganic metal oxides TiO2 and SnO2, the organic fullerene derivatives C60, 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.
|
|
| 6. |
- Mack, Michael J, et al.
(author)
-
Analysis of Stroke Occurring in the SYNTAX Trial Comparing Coronary Artery Bypass Surgery and Percutaneous Coronary Intervention in the Treatment of Complex Coronary Artery Disease
- 2013
-
In: JACC. Cardiovascular interventions. - : Elsevier BV. - 1936-8798. ; 6:4, s. 344-354
-
Journal article (peer-reviewed)abstract
- OBJECTIVES: This study sought to analyze stroke rates in the SYNTAX (Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery) trial's randomized and registry cohorts of patients being treated with coronary artery bypass grafting (CABG) or percutaneous coronary intervention (PCI) for treatment of complex coronary artery disease.BACKGROUND: The SYNTAX trial compared PCI to CABG in patients with de novo 3-vessel and/or left main coronary disease.METHODS: The SYNTAX randomized trial was conducted at 85 U.S. and European sites (n = 1,800). All strokes (up to 4 years) were independently adjudicated by a clinical events committee that included a neurologist. An additional 1,077 (of which 644 were followed for 5 years) and 198 patients were included in the CABG and PCI registries, respectively.RESULTS: In the randomized cohort, 31 CABG and 19 PCI patients experienced 33 and 20 strokes post-randomization at 4-year follow-up, respectively (p = 0.062). Three strokes occurred pre-procedurally but following randomization in CABG-treated patients. After CABG, a large proportion of strokes occurred acutely (0 to 30 days: 9 of 33), whereas in the PCI arm, most strokes occurred >30 days after the procedure (18 of 20). Stroke resulted in death in 3 patients in both the PCI and CABG groups. Of the patients who developed stroke, 68% (21 of 31) in the CABG group had residual deficits at discharge; in the PCI group, 47% (9 of 19) had residual deficits. In a multivariate analysis, treatment with CABG was not significantly associated with increased stroke rates (odds ratio: 1.67, 95% confidence interval: 0.93 to 3.01, p = 0.089). The incidence and outcomes of stroke were similar in the randomized trial and registries.CONCLUSIONS: There is a higher risk of periprocedural stroke in patients undergoing CABG versus PCI; however, the risk converges over the first 4 years of follow-up. (SYNTAX Study: TAXUS Drug-Eluting Stent Versus Coronary Artery Bypass Surgery for the Treatment of Narrowed Arteries; NCT00114972).
|
|
| 7. |
- Schröder, Vincent R.F., et al.
(author)
-
Bicolour, large area, inkjet-printed metal halide perovskite light emitting diodes
-
In: Materials Horizons. - 2051-6347.
-
Journal article (peer-reviewed)abstract
- We demonstrate a bicoloured metal halide perovskite (MHP) light emitting diode (LED) fabricated in two sequential inkjet printing steps. By adjusting the printing parameters, we selectively and deliberately redissolve and recrystallize the first printed emissive layer to add a pattern emitting in a different color. The red light emitting features (on a green light emitting background) have a minimum size of 100 μm and originate from iodide-rich domains in a phase-segregated, mixed MHP. This phase forms between the first layer, a bromide-based MHP, which is partially dissolved by printing, and the second layer, an iodide-containing MHP. With an optimised printing process we can retain the active layer integrity and fabricate bicolour, large area MHP-based LEDs with up to 1600 mm2 active area. The two emission peaks at 535 nm and 710 nm are well separated and produce a strong visual contrast.
|
|
| 8. |
- Schröder, Vincent R.F., et al.
(author)
-
Using Combinatorial Inkjet Printing for Synthesis and Deposition of Metal Halide Perovskites in Wavelength-Selective Photodetectors
- 2022
-
In: Advanced Engineering Materials. - : Wiley. - 1438-1656 .- 1527-2648. ; 24:4
-
Journal article (peer-reviewed)abstract
- Metal halide perovskites have received great attention in recent years, predominantly due to the high performance of perovskite solar cells. The versatility of the material, which allows the tunability of the bandgap, has led to its use in light-emitting diodes, photo, and X-ray detectors, among other optoelectronic device applications. Specifically in photodetectors, the tunability of the bandgap allows fabrication of spectrally selective devices. Utilizing a combinatorial inkjet printing approach, multiple perovskite compositions absorbing at specific wavelengths in a single printing step are fabricated. The drop-on-demand capabilities of inkjet printing enable the deposition of inks in a precise ratio to produce specific perovskite compositions in the printed thin film. By controlling the halide ratio in the compositions, a mixed halide gradient ranging from pure MAPbI3 via MAPbBr3 to MAPbCl3 is produced. The tunability in the absorption onset from 410 to 790 nm is demonstrated, covering the whole visible spectrum, with a precision of 8 nm steps for MAPb(BrxCl1−x)3 compositions. From this range of mixed halide perovskites, photodetectors which show spectral selectivity corresponding to the measured absorption onset are demonstrated, paving the way for use in a printed visible light spectrometer without the need for a dispersion element.
|
|
