Refine
Year of publication
Document Type
- Article (95)
- Postprint (13)
- Review (7)
- Monograph/Edited Volume (6)
- Other (6)
- Conference Proceeding (2)
- Part of Periodical (2)
- Preprint (1)
Keywords
- perovskite solar cells (8)
- photoluminescence (5)
- Gewalt (2)
- ISOS-L-1I protocol (2)
- Kriminalität (2)
- Nachhaltigkeit (2)
- PTH (2)
- Poecilia mexicana (2)
- Prävention (2)
- Rechtsextremismus (2)
- Solar cells (2)
- acute kidney injury (2)
- calibration (2)
- cesium lead halides (2)
- crime (2)
- crystal orientation (2)
- end-stage kidney disease (2)
- female choice (2)
- forest management (2)
- galaxies: evolution (2)
- gamma diversity (2)
- genome-wide association (2)
- global change (2)
- inorganic perovskites (2)
- interfacial recombination (2)
- intergalactic medium (2)
- n-oxPTH (2)
- non-independent mate choice (2)
- non-radiative interface recombination (2)
- phase purity (2)
- photostability (2)
- photovoltaic devices (2)
- predator recognition (2)
- prevention (2)
- quantification (2)
- rapid eGFRcrea decline (2)
- right-wing extremism (2)
- species richness (2)
- study (2)
- sustainability (2)
- thin films (2)
- validation (2)
- violence (2)
- water-balance (2)
- (Z)-isomer (1)
- 1769-1799 (1)
- 1829 (1)
- 1830 (1)
- 2D perovskites (1)
- ABSH-system (1)
- Accelerometry (1)
- Active inference (1)
- Air showers (1)
- Akademie der Wissenschaften (1)
- Alps (1)
- Arabidopsis thaliana (1)
- Archimedes (1)
- Artof (1)
- Automatic evaluation (1)
- BBAW (1)
- Bacterial growth efficiency (1)
- Biodiversity Exploratories (1)
- Biodiversity experiments (1)
- Biodiversity theory (1)
- Biosynthesis (1)
- C. elegans (1)
- CH center dot center dot center dot F hydrogen bonds (1)
- COVID-19 pandemic (1)
- Camelid single domain antibodies (1)
- Carbohydrate Metabolism (1)
- Carbon decomposition (1)
- Cardiac rehabilitation (1)
- Cardiovascular magnetic resonance (1)
- Carl Ritter (1)
- Cations (1)
- Cherenkov Telescopes (1)
- Chronic Renal Failure (1)
- Chronic Renal Failure in Children (1)
- Chylomicron (1)
- Chytridiomycota (1)
- Community ecology (1)
- Computational model (1)
- Computer Modeling (1)
- Conservation management (1)
- Continuous cultures (1)
- Coronary angiography (1)
- Coronary artery disease (1)
- Cost-effectiveness (1)
- Cryptomycota (1)
- Cyanobacteria (1)
- DNA barcoding (1)
- Daphnia magna (1)
- Decision-making (1)
- Design concepts (1)
- Disproportionating isozyme 2 (DPE2) dpe2-deficient plants (1)
- Donor materials (1)
- Dora-Maira (1)
- Dual mode theory (1)
- Ecological boundaries (1)
- Ecosystem functions and services (1)
- Ecotone hierarchy (1)
- Edge effects (1)
- Edition (1)
- Energy expenditure (1)
- Energy science and technology (1)
- England (1)
- Eurasian Dry Grassland Group (EDGG) (1)
- European Vegetation Archive (EVA) (1)
- Evapotranspiration (1)
- Event cognition (1)
- External quantum efficiency (1)
- FGF21 (1)
- Fagus sylvatica (1)
- Forecasting (1)
- Forschungskolleg (1)
- Framework quantitative ecology (1)
- Francis Lieber (1)
- Freshwater fungi (1)
- Functional traits (1)
- G3BP (1)
- GMYC (1)
- Genomic Mining (1)
- Geodynamics (1)
- Geographie (1)
- Geologie (1)
- Georg Foster (1)
- Global change (1)
- Glucanotransferase (1)
- Goal-anticipatory gaze (1)
- Graf Ferdinand von Galen (1)
- GrassPlot (1)
- Ground based gamma ray astronomy (1)
- Hasso Plattner Institute (1)
- Hasso-Plattner-Institut (1)
- Hemodialysis (1)
- Hill numbers (1)
- Hyperglycaemia (1)
- ISM: clouds (1)
- ISM: kinematics and dynamics (1)
- ISM: structure (1)
- ISM: supernova remnants (1)
- Infancy (1)
- Insulin resistance (1)
- Interdisciplinarity (1)
- Kidney Transplantation (1)
- Klausurtagung (1)
- LSU (1)
- Leaf Cell (1)
- Leaf litter (1)
- Leaf maltose content (1)
- Lipid droplet proteome (1)
- Lipolysis (1)
- Local Group (1)
- Low voltage losses (1)
- Magellanic Clouds (1)
- Maltose Metabolism (1)
- Maltose assay (1)
- Mathematik (1)
- Matter cycling (1)
- Matter dynamics (1)
- Metabolic Regulation (1)
- Metabolism (1)
- Meteorologie (1)
- Molecular dynamics (1)
- Monitoring programmes (1)
- Monoclonal antibodies (1)
- Mountain building (1)
- Multi-locus phylogeny (1)
- NZO (1)
- Neudatierung (1)
- Next generation Cherenkov telescopes (1)
- Obesity (1)
- Oligosaccharide (1)
- Oscar M. Lieber (1)
- Oxidation (1)
- Patholinguistik (1)
- Perovskites (1)
- Petra Werner (1)
- Ph.D. retreat (1)
- Phase transitions (1)
- PhenObs phenological network (1)
- Photolysis (1)
- Phylogeography (1)
- Physical activity (1)
- Picea abies (1)
- Pinus sylvestris (1)
- Plant Biochemistry (1)
- Poecile hypermelaenus (1)
- Poecile weigoldicus (1)
- Politik (1)
- Protein restriction (1)
- Pseudotsuga menziesii (1)
- Quorum Sensing (1)
- Raman spectroscopy (1)
- Reisetagebuch (1)
- Resonant inelastic X-ray scattering (1)
- Rozellomycota (1)
- Russland (1)
- Russland-Tagebuch (1)
- SIRT6 (1)
- Scintigraphy (1)
- Seismic imaging (1)
- Seismic network (1)
- Seismology (1)
- Service-oriented Systems Engineering (1)
- Sexual selection (1)
- Sibirien (1)
- Silage maize (1)
- Sirtuins (1)
- Solar energy (1)
- Spanien (1)
- Specialized (1)
- Sprachentwicklungsstörung (SES) (1)
- Spracherwerb (1)
- Sprachtherapie (1)
- Spring barley (1)
- Starch Degradation (1)
- Stress (1)
- Stress granules (1)
- Sublimation with good yield (1)
- TAVI (1)
- TeV gamma-ray astronomy (1)
- Triglyceride secretion (1)
- Ultrafast spectroscopy (1)
- V-OC loss (1)
- Winter oilseed rape (1)
- Winter wheat (1)
- Yields (1)
- Zahlentheorie (1)
- acid sphingomyelinase (1)
- adolescent growth (1)
- agency cues (1)
- aquatic fungi (1)
- bacterial growth (1)
- benthos (1)
- benzimidazoles (1)
- beta diversity (1)
- beta-amylase assay (1)
- biodiversity (1)
- biodiversity exploratories (1)
- biofilm (1)
- body mass (1)
- botanical gardens (1)
- bromeliads (1)
- capillarity (1)
- carbon cycle (1)
- cardiovascular magnetic resonance (1)
- ceramide (1)
- charge transport (1)
- child development (1)
- child growth (1)
- chronic renal failure (1)
- chronic renal failure in children (1)
- climate change (1)
- climate extremes (1)
- climate variability (1)
- cold neutrons (1)
- community ecology (1)
- complexes (1)
- conductivity (1)
- coronary angiography (1)
- coronary artery disease (1)
- corrinoid-containing enzymes (1)
- cosmology: observations (1)
- cost-effectiveness (1)
- dark ages, reionization, first stars (1)
- dark diversity (1)
- developing agentive self (1)
- disturbance (1)
- doping (1)
- driving force (1)
- dry grasslands (1)
- dumortierite (1)
- dynamics (1)
- ecological networks (1)
- electro-optical materials (1)
- electron spectroscopy (1)
- electronic-structure (1)
- electro‐optical materials (1)
- energy resolution (1)
- epidermis (1)
- epiphytes (1)
- errata, addenda (1)
- excess carbon (1)
- exercise capacity (1)
- extinction (1)
- eye tracking (1)
- first flowering day (1)
- food quality (1)
- forest conversion (1)
- forest specialists (1)
- fragmentation (1)
- frailty (1)
- fungal diversity (1)
- galaxies: ISM (1)
- galaxies: abundances (1)
- galaxies: active (1)
- galaxies: dwarf (1)
- galaxies: formation (1)
- galaxies: high-redshift (1)
- galaxies: individual (Large Magellanic Cloud, Small Magellanic Cloud) (1)
- galaxies: individual (M 87) (1)
- galaxies: interactions (1)
- galaxies: jets (1)
- galaxies: nuclei (1)
- gamma rays: galaxies (1)
- gamma rays: general (1)
- gender gap (1)
- glycoprotein GP2 (1)
- grassland vegetation (1)
- gross primary production (1)
- growing season length (1)
- growth efficiency (1)
- guild assembly (1)
- habitat specificity (1)
- height (1)
- hemodialysis (1)
- heterogeneity (1)
- hippocampus (1)
- homogenization (1)
- impairments of lexicon and semantics (1)
- infancy (1)
- insect decline (1)
- interface recombination (1)
- intrinsic motivation (1)
- iron(II) (1)
- kidney transplantation (1)
- l-edge xas (1)
- lake ecosystem (1)
- land-use (1)
- landscape scale (1)
- language acquisition (1)
- leaf (1)
- lexikalisch-semantische Störungen (1)
- macroecology (1)
- magnesiodumortierite (1)
- management (1)
- matter (1)
- meta-analysis (1)
- metabarcoding (1)
- methods: statistical (1)
- microbial carbon (1)
- molecular-structure (1)
- monitoring (1)
- multi-taxon (1)
- multidimensional complexity (1)
- multidiversity (1)
- nested plot (1)
- net primary production (1)
- niche theory (1)
- nitrogen deposition (1)
- non-fullerene acceptors (1)
- non-human grasping (1)
- onshore wind (1)
- open-circuit voltage (1)
- open‐circuit voltage (1)
- operant behavior (1)
- organic solar cells (1)
- oxidation (1)
- patholinguistics (1)
- phospholipids (1)
- photocurrent generation (1)
- phylogeny (1)
- plankton (1)
- planning constraints (1)
- plant respiration (1)
- polyunsaturated fatty acids (1)
- prediction (1)
- predictive gaze behavior (1)
- probe (1)
- quality of life (1)
- quasars: general (1)
- quasars: individual (PKS 0405-123) (1)
- quasi-permanent plot (1)
- radiation mechanisms: non-thermal (1)
- re-survey (1)
- reductive dehalogenase (1)
- reed (1)
- reproduction (1)
- research priorities (1)
- research school (1)
- resource assessments (1)
- sPlot (1)
- saproxylic beetles (1)
- scale-dependence (1)
- scintigraphy (1)
- sediment (1)
- service-oriented systems engineering (1)
- sexual selection (1)
- social acceptance (1)
- socio-economic environment (1)
- soil (1)
- somatic growth (1)
- spatial grain (1)
- specialisation (1)
- species accumulation curve (1)
- species distribution model (1)
- species interactions (1)
- species turnover (1)
- species-area relationship (SAR) (1)
- specific language impairment (SLI) (1)
- spectra (1)
- speech and language therapy (1)
- sphingomyelin (1)
- spin-state (1)
- stoichiometric controls (1)
- surveys (1)
- synchrotron (1)
- synthesis (1)
- techniques: image processing (1)
- temperate forests (1)
- terrestrial ecosystems (1)
- tetrahedral boron (1)
- time of flight (1)
- tool-use actions (1)
- trait-based community modules (1)
- traits (1)
- transport layers (1)
- tree species diversity (1)
- trichomes (1)
- trophic interactions (1)
- ultrahigh-pressure (UHP) (1)
- vegetation-plot database (1)
- vitamin B-12 (1)
- water (1)
- water movement (1)
- water sample (1)
- weight (1)
- wet grasslands (1)
- wide angle (1)
Institute
- Institut für Physik und Astronomie (38)
- Institut für Biochemie und Biologie (33)
- Institut für Geowissenschaften (12)
- Institut für Chemie (7)
- Institut für Umweltwissenschaften und Geographie (7)
- Institut für Informatik und Computational Science (5)
- Mathematisch-Naturwissenschaftliche Fakultät (5)
- Department Sport- und Gesundheitswissenschaften (4)
- Hasso-Plattner-Institut für Digital Engineering GmbH (4)
- Historisches Institut (4)
2D Ruddlesden-Popper perovskite (RPP) solar cells have excellent environmental stability. However, the power conversion efficiency (PCE) of RPP cells remains inferior to 3D perovskite-based cells. Herein, 2D (CH3(CH2)(3)NH3)(2)(CH3NH3)(n-1)PbnI3n+1 perovskite cells with different numbers of [PbI6](4-) sheets (n = 2-4) are analyzed. Photoluminescence quantum yield (PLQY) measurements show that nonradiative open-circuit voltage (V-OC) losses outweigh radiative losses in materials with n > 2. The n = 3 and n = 4 films exhibit a higher PLQY than the standard 3D methylammonium lead iodide perovskite although this is accompanied by increased interfacial recombination at the top perovskite/C-60 interface. This tradeoff results in a similar PLQY in all devices, including the n = 2 system where the perovskite bulk dominates the recombination properties of the cell. In most cases the quasi-Fermi level splitting matches the device V-OC within 20 meV, which indicates minimal recombination losses at the metal contacts. The results show that poor charge transport rather than exciton dissociation is the primary reason for the reduction in fill factor of the RPP devices. Optimized n = 4 RPP solar cells had PCEs of 13% with significant potential for further improvements.
The incorporation of even small amounts of strontium (Sr) into lead-base hybrid quadruple cation perovskite solar cells results in a systematic increase of the open circuit voltage (V-oc) in pin-type perovskite solar cells. We demonstrate via absolute and transient photoluminescence (PL) experiments how the incorporation of Sr significantly reduces the non-radiative recombination losses in the neat perovskite layer. We show that Sr segregates at the perovskite surface, where it induces important changes of morphology and energetics. Notably, the Sr-enriched surface exhibits a wider band gap and a more n-type character, accompanied with significantly stronger surface band bending. As a result, we observe a significant increase of the quasi-Fermi level splitting in the neat perovskite by reduced surface recombination and more importantly, a strong reduction of losses attributed to non-radiative recombination at the interface to the C-60 electron-transporting layer. The resulting solar cells exhibited a V-oc of 1.18 V, which could be further improved to nearly 1.23 V through addition of a thin polymer interlayer, reducing the non-radiative voltage loss to only 110 meV. Our work shows that simply adding a small amount of Sr to the precursor solutions induces a beneficial surface modification in the perovskite, without requiring any post treatment, resulting in high efficiency solar cells with power conversion efficiency (PCE) up to 20.3%. Our results demonstrate very high V-oc values and efficiencies in Sr-containing quadruple cation perovskite pin-type solar cells and highlight the imperative importance of addressing and minimizing the recombination losses at the interface between perovskite and charge transporting layer.
Today's perovskite solar cells (PSCs) are limited mainly by their open‐circuit voltage (VOC) due to nonradiative recombination. Therefore, a comprehensive understanding of the relevant recombination pathways is needed. Here, intensity‐dependent measurements of the quasi‐Fermi level splitting (QFLS) and of the VOC on the very same devices, including pin‐type PSCs with efficiencies above 20%, are performed. It is found that the QFLS in the perovskite lies significantly below its radiative limit for all intensities but also that the VOC is generally lower than the QFLS, violating one main assumption of the Shockley‐Queisser theory. This has far‐reaching implications for the applicability of some well‐established techniques, which use the VOC as a measure of the carrier densities in the absorber. By performing drift‐diffusion simulations, the intensity dependence of the QFLS, the QFLS‐VOC offset and the ideality factor are consistently explained by trap‐assisted recombination and energetic misalignment at the interfaces. Additionally, it is found that the saturation of the VOC at high intensities is caused by insufficient contact selectivity while heating effects are of minor importance. It is concluded that the analysis of the VOC does not provide reliable conclusions of the recombination pathways and that the knowledge of the QFLS‐VOC relation is of great importance.
Perovskite solar cells (PSCs) are one of the main research topics of the photovoltaic community; with efficiencies now reaching up to 24%, PSCs are on the way to catching up with classical inorganic solar cells. However, PSCs have not yet reached their full potential. In fact, their efficiency is still limited by nonradiative recombination, mainly via trap-states and by losses due to the poor transport properties of the commonly used transport layers (TLs). Indeed, state-of-the-art TLs (especially if organic) suffer from rather low mobilities, typically within 10(-5) and 10(-2) cm(-2) V-1 s(-1), when compared to the high mobilities, 1-10 cm(-2) V-1 s(-1), measured for perovskites. This work presents a comprehensive analysis of the effect of the mobility, thickness, and doping density of the transport layers based on combined experimental and modeling results of two sets of devices made of a solution-processed high-performing triple-cation (PCE approximate to 20%). The results are also cross-checked on vacuum-processed MAPbI(3) devices. From this analysis, general guidelines on how to optimize a TL are introduced and especially a new and simple formula to easily calculate the amount of doping necessary to counterbalance the low mobility of the TLs.
Charge extraction in organic solar cells (OSCs) is commonly believed to be limited by bimolecular recombination of photogenerated charges. However, the fill factor of OSCs is usually almost entirely governed by recombination processes that scale with the first order of the light intensity. This linear loss was often interpreted to be a consequence of geminate or trap-assisted recombination. Numerical simulations show that this linear dependence is a direct consequence of the large amount of excess dark charge near the contact. The first-order losses increase with decreasing mobility of minority carriers, and we discuss the impact of several material and device parameters on this loss mechanism. This work highlights that OSCs are especially vulnerable to injected charges as a result of their poor charge transport properties. This implies that dark charges need to be better accounted for when interpreting electro-optical measurements and charge collection based on simple figures of merit.
Organic solar cells are currently experiencing a second golden age thanks to the development of novel non-fullerene acceptors (NFAs). Surprisingly, some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein, free charge generation in the high-performance blend of the donor polymer PM6 with the NFA Y6 is thoroughly investigated as a function of internal field, temperature and excitation energy. Results show that photocurrent generation is essentially barrierless with near-unity efficiency, regardless of excitation energy. Efficient charge separation is maintained over a wide temperature range, down to 100 K, despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA, measurements of the energetic disorder, and theoretical modeling suggest that CT state dissociation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier.
Perovskite solar cells now compete with their inorganic counterparts in terms of power conversion efficiency, not least because of their small open-circuit voltage (V-OC) losses. A key to surpass traditional thin-film solar cells is the fill factor (FF). Therefore, more insights into the physical mechanisms that define the bias dependence of the photocurrent are urgently required. In this work, we studied charge extraction and recombination in efficient triple cation perovskite solar cells with undoped organic electron/hole transport layers (ETL/HTL). Using integral time of flight we identify the transit time through the HTL as the key figure of merit for maximizing the fill factor (FF) and efficiency. Complementarily, intensity dependent photocurrent and V-OC measurements elucidate the role of the HTL on the bias dependence of non-radiative and transport-related loss channels. We show that charge transport losses can be completely avoided under certain conditions, yielding devices with FFs of up to 84%. Optimized cells exhibit power conversion efficiencies of above 20% for 6 mm(2) sized pixels and 18.9% for a device area of 1 cm(2). These are record efficiencies for hybrid perovskite devices with dopant-free transport layers, highlighting the potential of this device technology to avoid charge-transport limitations and to approach the Shockley-Queisser limit.
Perovskite solar cells combine high carrier mobilities with long carrier lifetimes and high radiative efficiencies. Despite this, full devices suffer from significant nonradiative recombination losses, limiting their VOC to values well below the Shockley–Queisser limit. Here, recent advances in understanding nonradiative recombination in perovskite solar cells from picoseconds to steady state are presented, with an emphasis on the interfaces between the perovskite absorber and the charge transport layers. Quantification of the quasi‐Fermi level splitting in perovskite films with and without attached transport layers allows to identify the origin of nonradiative recombination, and to explain the VOC of operational devices. These measurements prove that in state‐of‐the‐art solar cells, nonradiative recombination at the interfaces between the perovskite and the transport layers is more important than processes in the bulk or at grain boundaries. Optical pump‐probe techniques give complementary access to the interfacial recombination pathways and provide quantitative information on transfer rates and recombination velocities. Promising optimization strategies are also highlighted, in particular in view of the role of energy level alignment and the importance of surface passivation. Recent record perovskite solar cells with low nonradiative losses are presented where interfacial recombination is effectively overcome—paving the way to the thermodynamic efficiency limit.
Perovskite solar cells combine high carrier mobilities with long carrier lifetimes and high radiative efficiencies. Despite this, full devices suffer from significant nonradiative recombination losses, limiting their V-OC to values well below the Shockley-Queisser limit. Here, recent advances in understanding nonradiative recombination in perovskite solar cells from picoseconds to steady state are presented, with an emphasis on the interfaces between the perovskite absorber and the charge transport layers. Quantification of the quasi-Fermi level splitting in perovskite films with and without attached transport layers allows to identify the origin of nonradiative recombination, and to explain the V-OC of operational devices. These measurements prove that in state-of-the-art solar cells, nonradiative recombination at the interfaces between the perovskite and the transport layers is more important than processes in the bulk or at grain boundaries. Optical pump-probe techniques give complementary access to the interfacial recombination pathways and provide quantitative information on transfer rates and recombination velocities. Promising optimization strategies are also highlighted, in particular in view of the role of energy level alignment and the importance of surface passivation. Recent record perovskite solar cells with low nonradiative losses are presented where interfacial recombination is effectively overcome-paving the way to the thermodynamic efficiency limit.
Perovskite solar cells (PSCs) are currently one of the most promising photovoltaic technologies for highly efficient and cost-effective solar energy production. In only a few years, an unprecedented progression of preparation procedures and material compositions delivered lab-scale devices that have now reached record power conversion efficiencies (PCEs) higher than 20%, competing with most established solar cell materials such as silicon, CIGS, and CdTe. However, despite a large number of researchers currently involved in this topic, only a few groups in the world can reproduce >20% efficiencies on a regular n-i-p architecture. In this work, we present detailed protocols for preparing PSCs in regular (n-i-p) and inverted (p-i-n) architectures with >= 20% PCE. We aim to provide a comprehensive, reproducible description of our device fabrication , protocols. We encourage the practice of reporting detailed and transparent protocols that can be more easily reproduced by other laboratories. A better reporting standard may, in turn, accelerate the development of perovskite solar cells and related research fields.
The performance of perovskite solar cells is predominantly limited by non-radiative recombination, either through trap-assisted recombination in the absorber layer or via minority carrier recombination at the perovskite/transport layer interfaces. Here, we use transient and absolute photoluminescence imaging to visualize all non-radiative recombination pathways in planar pintype perovskite solar cells with undoped organic charge transport layers. We find significant quasi-Fermi-level splitting losses (135 meV) in the perovskite bulk, whereas interfacial recombination results in an additional free energy loss of 80 meV at each individual interface, which limits the open-circuit voltage (V-oc) of the complete cell to similar to 1.12 V. Inserting ultrathin interlayers between the perovskite and transport layers leads to a substantial reduction of these interfacial losses at both the p and n contacts. Using this knowledge and approach, we demonstrate reproducible dopant-free 1 cm(2) perovskite solar cells surpassing 20% efficiency (19.83% certified) with stabilized power output, a high V-oc (1.17 V) and record fill factor (>81%).
Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit.
Multijunction solar cells can overcome the fundamental efficiency limits of single-junction devices. The bandgap tunability of metal halide perovskite solar cells renders them attractive for multijunction architectures(1). Combinations with silicon and copper indium gallium selenide (CIGS), as well as all-perovskite tandem cells, have been reported(2-5). Meanwhile, narrow-gap non-fullerene acceptors have unlocked skyrocketing efficiencies for organic solar cells(6,7). Organic and perovskite semiconductors are an attractive combination, sharing similar processing technologies. Currently, perovskite-organic tandems show subpar efficiencies and are limited by the low open-circuit voltage (V-oc) of wide-gap perovskite cells(8) and losses introduced by the interconnect between the subcells(9,10). Here we demonstrate perovskite-organic tandem cells with an efficiency of 24.0 per cent (certified 23.1 per cent) and a high V-oc of 2.15 volts. Optimized charge extraction layers afford perovskite subcells with an outstanding combination of high V-oc and fill factor. The organic subcells provide a high external quantum efficiency in the near-infrared and, in contrast to paradigmatic concerns about limited photostability of non-fullerene cells(11), show an outstanding operational stability if excitons are predominantly generated on the non-fullerene acceptor, which is the case in our tandems. The subcells are connected by an ultrathin (approximately 1.5 nanometres) metal-like indium oxide layer with unprecedented low optical/electrical losses. This work sets a milestone for perovskite-organic tandems, which outperform the best p-i-n perovskite single junctions(12) and are on a par with perovskite-CIGS and all-perovskite multijunctions(13).
Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit.
In crystalline and amorphous semiconductors, the temperature-dependent Urbach energy can be determined from the inverse slope of the logarithm of the absorption spectrum and reflects the static and dynamic energetic disorder. Using recent advances in the sensitivity of photocurrent spectroscopy methods, we elucidate the temperature-dependent Urbach energy in lead halide perovskites containing different numbers of cation components. We find Urbach energies at room temperature to be 13.0 +/- 1.0, 13.2 +/- 1.0, and 13.5 +/- 1.0 meV for single, double, and triple cation perovskite. Static, temperature-independent contributions to the Urbach energy are found to be as low as 5.1 ?+/- 0.5, 4.7 +/- 0.3, and 3.3 +/- 0.9 meV for the same systems. Our results suggest that, at a low temperature, the dominant static disorder in perovskites is derived from zero-point phonon energy rather than structural disorder. This is unusual for solution-processed semiconductors but broadens the potential application of perovskites further to quantum electronics and devices.
The fate of allochthonous dissolved organic carbon (DOC) in aquatic systems is primarily controlled by the turnover of heterotrophic bacteria. However, the roles that abiotic and biotic factors such as light and DOC release by aquatic primary producers play in the microbial decomposition of allochthonous DOC is not well understood. We therefore tested if light and autochthonous DOC additions would increase allochthonous DOC decomposition rates and change bacterial growth efficiencies and community composition (BCC). We established continuous growth cultures with different inocula of natural bacterial communities and alder leaf leachates (DOCleaf) with and without light exposure before amendment. Furthermore, we incubated DOCleaf together with autochthonous DOC from lysed phytoplankton cultures (DOCphyto). Our results revealed that pretreatments of DOCleaf with light resulted in a doubling of bacterial growth efficiency (BGE), whereas additions of DOCphyto or combined additions of DOCphyto and light had no effect on BGE. The change in BGE was not accompanied by shifts in the phylogenetic structure of the BCC, but BCC was influenced by the DOC source. Our results highlight that a doubling of BGE is not necessarily accompanied by a shift in BCC and that BCC is more strongly affected by resource properties.
Freshwater fungi are a poorly studied ecological group that includes a high taxonomic diversity. Most studies on aquatic fungal diversity have focused on single habitats, thus the linkage between habitat heterogeneity and fungal diversity remains largely unexplored. We took 216 samples from 54 locations representing eight different habitats in the meso-oligotrophic, temperate Lake Stechlin in North-East Germany. These included the pelagic and littoral water column, sediments, and biotic substrates. We performed high throughput sequencing using the Roche 454 platform, employing a universal eukaryotic marker region within the large ribosomal subunit (LSU) to compare fungal diversity, community structure, and species turnover among habitats. Our analysis recovered 1027 fungal OTUs (97% sequence similarity). Richness estimates were highest in the sediment, biofilms, and benthic samples (189-231 OTUs), intermediate in water samples (42-85 OTUs), and lowest in plankton samples (8 OTUs). NMDS grouped the eight studied habitats into six clusters, indicating that community composition was strongly influenced by turnover among habitats. Fungal communities exhibited changes at the phylum and order levels along three different substrate categories from littoral to pelagic habitats. The large majority of OTUs (> 75%) could not be classified below the order level due to the lack of aquatic fungal entries in public sequence databases. Our study provides a first estimate of lake-wide fungal diversity and highlights the important contribution of habitat heterogeneity to overall diversity and community composition. Habitat diversity should be considered in any sampling strategy aiming to assess the fungal diversity of a water body.
Crop model intercomparison studies have mostly focused on the assessment of predictive capabilities for crop development using weather and basic soil data from the same location. Still challenging is the model performance when considering complex interrelations between soil and crop dynamics under a changing climate. The objective of this study was to test the agronomic crop and environmental flux-related performance of a set of crop models. The aim was to predict weighing lysimeter-based crop (i.e., agronomic) and water-related flux or state data (i.e., environmental) obtained for the same soil monoliths that were taken from their original environment and translocated to regions with different climatic conditions, after model calibration at the original site. Eleven models were deployed in the study. The lysimeter data (2014-2018) were from the Dedelow (Dd), Bad Lauchstadt (BL), and Selhausen (Se) sites of the TERENO (TERrestrial ENvironmental Observatories) SOILCan network. Soil monoliths from Dd were transferred to the drier and warmer BL site and the wetter and warmer Se site, which allowed a comparison of similar soil and crop under varying climatic conditions. The model parameters were calibrated using an identical set of crop- and soil-related data from Dd. Environmental fluxes and crop growth of Dd soil were predicted for conditions at BL and Se sites using the calibrated models. The comparison of predicted and measured data of Dd lysimeters at BL and Se revealed differences among models. At site BL, the crop models predicted agronomic and environmental components similarly well. Model performance values indicate that the environmental components at site Se were better predicted than agronomic ones. The multi-model mean was for most observations the better predictor compared with those of individual models. For Se site conditions, crop models failed to predict site-specific crop development indicating that climatic conditions (i.e., heat stress) were outside the range of variation in the data sets considered for model calibration. For improving predictive ability of crop models (i.e., productivity and fluxes), more attention should be paid to soil-related data (i.e., water fluxes and system states) when simulating soil-crop-climate interrelations in changing climatic conditions.
Maltose frequently occurs as intermediate of the central carbon metabolism of prokaryotic and eukaryotic cells. Various mutants possess elevated maltose levels. Maltose exists as two anomers, (alpha- and beta-form) which are rapidly interconverted without requiring enzyme-mediated catalysis. As maltose is often abundant together with other oligoglucans, selective quantification is essential. In this communication, we present a photometric maltose assay using 4-alpha-glucanotransferase (AtDPE2) from Arabidopsis thaliana. Under in vitro conditions, AtDPE2 utilizes maltose as glucosyl donor and glycogen as acceptor releasing the other hexosyl unit as free glucose which is photometrically quantified following enzymatic phosphorylation and oxidation. Under the conditions used, DPE2 does not noticeably react with other di- or oligosaccharides. Selectivity compares favorably with that of maltase frequently used in maltose assays. Reducing end interconversion of the two maltose anomers is in rapid equilibrium and, therefore, the novel assay measures total maltose contents. Furthermore, an AtDPE2-based continuous photometric assay is presented which allows to quantify beta-amylase activity and was found to be superior to a conventional test. Finally, the AtDPE2-based maltose assay was used to quantify leaf maltose contents of both Arabidopsis wild type and AtDPE2-deficient plants throughout the light-dark cycle. These data are presented together with assimilatory starch levels. (C) 2017 Published by Elsevier Inc.
Phenology has emerged as key indicator of the biological impacts of climate change, yet the role of functional traits constraining variation in herbaceous species' phenology has received little attention. Botanical gardens are ideal places in which to investigate large numbers of species growing under common climate conditions. We ask whether interspecific variation in plant phenology is influenced by differences in functional traits. We recorded onset, end, duration and intensity of initial growth, leafing out, leaf senescence, flowering and fruiting for 212 species across five botanical gardens in Germany. We measured functional traits, including plant height, absolute and specific leaf area, leaf dry matter content, leaf carbon and nitrogen content and seed mass and accounted for species' relatedness. Closely related species showed greater similarities in timing of phenological events than expected by chance, but species' traits had a high degree of explanatory power, pointing to paramount importance of species' life-history strategies. Taller plants showed later timing of initial growth, and flowered, fruited and underwent leaf senescence later. Large-leaved species had shorter flowering and fruiting durations. Taller, large-leaved species differ in their phenology and are more competitive than smaller, small-leaved species. We assume climate warming will change plant communities' competitive hierarchies with consequences for biodiversity.
Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA.
Technical report
(2019)
Design and Implementation of service-oriented architectures imposes a huge number of research questions from the fields of software engineering, system analysis and modeling, adaptability, and application integration. Component orientation and web services are two approaches for design and realization of complex web-based system. Both approaches allow for dynamic application adaptation as well as integration of enterprise application.
Commonly used technologies, such as J2EE and .NET, form de facto standards for the realization of complex distributed systems. Evolution of component systems has lead to web services and service-based architectures. This has been manifested in a multitude of industry standards and initiatives such as XML, WSDL UDDI, SOAP, etc. All these achievements lead to a new and promising paradigm in IT systems engineering which proposes to design complex software solutions as collaboration of contractually defined software services.
Service-Oriented Systems Engineering represents a symbiosis of best practices in object-orientation, component-based development, distributed computing, and business process management. It provides integration of business and IT concerns.
The annual Ph.D. Retreat of the Research School provides each member the opportunity to present his/her current state of their research and to give an outline of a prospective Ph.D. thesis. Due to the interdisciplinary structure of the research school, this technical report covers a wide range of topics. These include but are not limited to: Human Computer Interaction and Computer Vision as Service; Service-oriented Geovisualization Systems; Algorithm Engineering for Service-oriented Systems; Modeling and Verification of Self-adaptive Service-oriented Systems; Tools and Methods for Software Engineering in Service-oriented Systems; Security Engineering of Service-based IT Systems; Service-oriented Information Systems; Evolutionary Transition of Enterprise Applications to Service Orientation; Operating System Abstractions for Service-oriented Computing; and Services Specification, Composition, and Enactment.
The 2010 very high energy gamma-ray flare and 10 years ofmulti-wavelength oservations of M 87
(2012)
The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3-6) x 10(9) M-circle dot) provides a unique opportunity to investigate the origin of very high energy (VHE; E > 100 GeV) gamma-ray emission generated in relativistic outflows and the surroundings of supermassive black holes. M 87 has been established as a VHE gamma-ray emitter since 2006. The VHE gamma-ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz Very Long Baseline Array, VLBA). The excellent sampling of the VHE gamma-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of tau(rise)(d) = (1.69 +/- 0.30) days and tau(decay)(d) = (0.611 +/- 0.080) days, respectively. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (similar to day), peak fluxes (Phi(>0.35 TeV) similar or equal to (1-3) x 10(-11) photons cm(-2) s(-1)), and VHE spectra. VLBA radio observations of 43 GHz of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken similar to 3 days after the peak of the VHE gamma-ray emission reveal an enhanced flux from the core (flux increased by factor similar to 2; variability timescale <2 days). The long-term (2001-2010) multi-wavelength (MWL) light curve of M 87, spanning from radio to VHE and including data from Hubble Space Telescope, Liverpool Telescope, Very Large Array, and European VLBI Network, is used to further investigate the origin of the VHE gamma-ray emission. No unique, common MWL signature of the three VHE flares has been identified. In the outer kiloparsec jet region, in particular in HST-1, no enhanced MWL activity was detected in 2008 and 2010, disfavoring it as the origin of the VHE flares during these years. Shortly after two of the three flares (2008 and 2010), the X-ray core was observed to be at a higher flux level than its characteristic range (determined from more than 60 monitoring observations: 2002-2009). In 2005, the strong flux dominance of HST-1 could have suppressed the detection of such a feature. Published models for VHE gamma-ray emission from M 87 are reviewed in the light of the new data.
Der vorliegende Tagungsband enthält alle Beiträge des 1. Herbsttreffens Patholinguistik, das am 24.11.2007 an der Universität Potsdam stattgefunden hat. Sowohl die drei Hauptvorträge zum Thema „Der Erwerb von Lexikon und Semantik – Meilensteine, Störungen und Therapie“ als auch die Kurzvorträge promovierter Patholinguisten sind ausführlich dokumentiert. Außerdem enthält der Tagungsband die Abstracts der präsentierten Poster.
Cosmic-ray neutron sensing (CRNS) allows for the estimation of root-zone soil water content (SWC) at the scale of several hectares. In this paper, we present the data recorded by a dense CRNS network operated from 2019 to 2022 at an agricultural research site in Marquardt, Germany - the first multi-year CRNS cluster. Consisting, at its core, of eight permanently installed CRNS sensors, the cluster was supplemented by a wealth of complementary measurements: data from seven additional temporary CRNS sensors, partly co-located with the permanent ones; 27 SWC profiles (mostly permanent); two groundwater observation wells; meteorological records; and Global Navigation Satellite System reflectometry (GNSS-R). Complementary to these continuous measurements, numerous campaign-based activities provided data by mobile CRNS roving, hyperspectral im-agery via UASs, intensive manual sampling of soil properties (SWC, bulk density, organic matter, texture, soil hydraulic properties), and observations of biomass and snow (cover, depth, and density). The unique temporal coverage of 3 years entails a broad spectrum of hydro-meteorological conditions, including exceptional drought periods and extreme rainfall but also episodes of snow coverage, as well as a dedicated irrigation experiment. Apart from serving to advance CRNS-related retrieval methods, this data set is expected to be useful for vari-ous disciplines, for example, soil and groundwater hydrology, agriculture, or remote sensing. Hence, we show exemplary features of the data set in order to highlight the potential for such subsequent studies. The data are available at doi.org/10.23728/b2share.551095325d74431881185fba1eb09c95 (Heistermann et al., 2022b).
Most image restoration methods in astronomy rely upon probabilistic tools that infer the best solution for a deconvolution problem. They achieve good performances when the point spread function (PSF) is spatially invariant in the image plane.
However, this condition is not always satisfied in real optical systems. We propose a new method for the restoration of images affected by static and anisotropic aberrations using Deep Neural Networks that can be directly applied to sky images.
The network is trained using simulated sky images corresponding to the T80-S Telescope optical model, a 80-cm survey imager at Cerro Tololo (Chile), which are synthesized using a Zernike polynomial representation of the optical system.
Once trained, the network can be used directly on sky images, outputting a corrected version of the image that has a constant and known PSF across its field of view. The method is to be tested on the T80-S Telescope.
We present the method and results on synthetic data.