Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology

Impedance spectroscopy (IS) has great potential to become a standard technique for the characterisation, analysis, and diagnosis of perovskite solar cells (PSC).

A key breakthrough in modern electronics was the introduction of band structure engineering, the design of almost arbitrary electronic potential structures by alloying different semiconductors to continuously tune the band gap and band-edge energies. Implementation of this approach in organic semiconductors has been hindered by strong localization of the electronic states in these materials. We show that the influence of so far largely ignored long-range Coulomb interactions provides a workaround. Photoelectron spectroscopy confirms that the ionization energies of crystalline organic semiconductors can be continuously tuned over a wide range by blending them with their halogenated derivatives. Correspondingly, the photovoltaic gap and open-circuit voltage of organic solar cells can be continuously tuned by the blending ratio of these donors.

This paper introduces the design of an ultra fast x-ray tomography scanner based on electron beam technology. The scanner has been developed for two-phase flow studies where frame rates of 1 kHz and higher are required. Its functional principle is similar to that of the electron beam x-ray CT scanners used in cardiac imaging. Thus, the scanner comprises an electron beam generator with a fast beam deflection unit, a semicircular x-ray production target made of tungsten alloy and a circular x-ray detector consisting of 240 CZT elements with 1.5 mm × 1.5 mm × 1.5 mm size each. The design is optimized with respect to ultra fast imaging of smaller flow vessels, such as pipes or laboratory-scale chemical reactors. In that way, the scanner is capable of scanning flow cross-sections at a speed of a few thousand frames per second which is sufficient to capture flows of a few meters per second velocity.

Transmission line pulsing (TLP) is well-established for the IV-characterization of electrostatic discharge (ESD)-protection elements. There still is a significant gap between the performance of present TLP-systems and the demands of the charged device model (CDM). A very fast, narrow-pulse (>3.5 ns), high-current TLP (VF-TLP) is designed to reduce this gap. It is feasible to study the pulsed breakdown of gate oxides and to determine at least the quasistatic IV-characteristics of input structures. Gate oxide breakdown is monitored within the first 6 ns of stress. Correlation with CDM (noncontact, nonsocketed) tests and socket discharge model [(SDM) formerly socketed CDM] is achieved in terms of the failure signature. However, the failure thresholds of VF-TLP and CDM/SDM do not correlate due to the different current paths. In the CDM, mobile charge is injected into or coming out of one pin until the full device is at same potential. In the SDM, the full test board is charged and discharged across the device. The VF-TLP current flows between the stress pin and a reference pin for the duration of the square pulse.

Abstract Ambient energy harvesting has great potential to contribute to sustainable development and address growing environmental challenges. Converting waste energy from energy-intensive processes and systems (e.g. combustion engines and furnaces) is crucial to reducing their environmental impact and achieving net-zero emissions. Compact energy harvesters will also be key to powering the exponentially growing smart devices ecosystem that is part of the Internet of Things, thus enabling futuristic applications that can improve our quality of life (e.g. smart homes, smart cities, smart manufacturing, and smart healthcare). To achieve these goals, innovative materials are needed to efficiently convert ambient energy into electricity through various physical mechanisms, such as the photovoltaic effect, thermoelectricity, piezoelectricity, triboelectricity, and radiofrequency wireless power transfer. By bringing together the perspectives of experts in various types of energy harvesting materials, this Roadmap provides extensive insights into recent advances and present challenges in the field. Additionally, the Roadmap analyses the key performance metrics of these technologies in relation to their ultimate energy conversion limits. Building on these insights, the Roadmap outlines promising directions for future research to fully harness the potential of energy harvesting materials for green energy anytime, anywhere.

The internet of things revolution requires efficient, easy-to-integrate energy harvesting. Here, we report indoor power generation by flexible perovskite solar cells (PSCs) manufactured on roll-to-roll indium-doped tin oxide (ITO)-coated ultra-thin flexible glass (FG) substrates with notable transmittance (>80%), sheet resistance (13 Ω/square), and bendability, surpassing 1,600 bending procedures at 20.5-mm curvature. Optimized PSCs on FG incorporate a mesoporous scaffold over SnO2 compact layers delivering efficiencies of 20.6% (16.7 μW⋅cm−2 power density) and 22.6% (35.0 μW⋅cm−2) under 200 and 400 lx LED illumination, respectively. These represent, to the best of our knowledge, the highest reported for any indoor flexible solar cell technology, surpassing by a 60%–90% margin the prior best-performing flexible PSCs. Specific powers (W/g) delivered by these lightweight cells are 40%–55% higher than their counterparts on polyethylene terephthalate (PET) films and an order of magnitude greater than those on rigid glass, highlighting the potential of flexible FG-PSCs as a key enabling technology for powering indoor electronics of the future.

An ultra-thin MoO3–Au–Ag wetting layer metal electrode is investigated to eliminate present optical and electrical limitations of inverted top-emitting OLEDs. Its high transmittance suppresses microcavity effects and the MoO3 hole injection layer compensates limited charge injection from the top contact. Overall, an extensive approach is presented to solve the key problems of top-emitting OLEDs in general.

Part 5 of the International Standard ISO/IEC 13818 `Generic Coding of Moving Pictures and Associated Audio' (MPEG-2) is a Technical Report, a sample software implementation of the procedures in parts 1, 2 and 3 of the standard (systems, video, and audio). This paper focuses on the video software, which gives an example of a fully compliant implementation of the standard and of a good video quality encoder, and serves as a tool for compliance testing. The implementation and some of the development aspects of the codec are described. The encoder is based on Test Model 5 (TM5), one of the best, published, non-proprietary coding models, which was used during MPEG-2 collaborative stage to evaluate proposed algorithms and to verify the syntax. The most important part of the Test Model is controlling the quantization parameter based on the image content and bit rate constraints under both signal-to-noise and psycho-optical aspects. The decoder has been successfully tested for compliance with the MPEG-2 standard, using the ISO/IEC MPEG verification and compliance bitstream test suites as stimuli.

The dynamic behavior of microfluid devices like miniaturized diaphragm pumps, microvalves and flow channels will be discussed. Special interest is directed to the dynamics of microminiaturized diaphragm pumps. A formalism will be given, which allows the evaluation of the interaction between these pumps and the connected fluid system. The results of the simulation will be compared with transient pressure measurements on pneumatically and electrostatically actuated diaphragm pumps on the millisecond time scale. It will be outlined how the dynamic behavior of more complex fluid systems can be described. Hence the hydraulic simulation of chemical analysis systems, consisting of several micropumps, flow channels, sensing and mixing elements becomes possible in the future.

Models for the simulation of complex fabrication steps for IC manufacture together with a simulation program are described. Multistep processes including ion implantation, oxidation, diffusion, and etching can be simulated, giving the doping profile, junction depth, and sheet resistivity. The program can also be applied to extract data from experimental results. The models used include the field enhancement of the diffusion together with the vacancy enhancement and the complex retardation for arsenic and boron.

Ultra-high molecular weight polyethylene (UHMWPE) was irradiated with accelerated electrons (1 MeV in air) using high dose rates (> 25 kGy/min) and thin specimens (thickness 1 mm). Parts of the specimens were remelted (200 degrees C for 10 min; 150 degrees C for 0, 2, 10, 30, 60 min). All specimens were stored in nitrogen in the dark at 5 degrees C. Supermolecular structure, extent of crosslinking, oxidative degradation, and macroradical content were studied by a number of methods (SAXS, WAXS, SEM, DSC, FTIR, ESR, TGA, solubility experiments, image analysis). The results obtained with irradiated samples were compared with those obtained with irradiated and remelted samples. It was confirmed that crosslinking predominates over chain scission at very high dose rates, even if the irradiation is performed in air. Discrepancies concerning supermolecular structure changes in UHMWPE after irradiation and thermal treatment, found in various studies in the literature, are discussed. A simple model, which describes and explains all supermolecular structure changes, is introduced. An effective way of eliminating residual macroradicals in UHMWPE is proposed.

Abstract Effective transparent barrier/encapsulation systems represent a key enabling technology for large‐area electronics. Securing stability to the environment is vital. Here, the effects of architectures, application processes, and water vapor transmission rates (WVTR) of transparent flexible ultra‐high permeation barrier films (UHPBF) applied to substrates with adhesive resins are unraveled for attaining long lifetime, and compared with polyethylene terephthalate and glass barriers. How strongly performance of barrier/adhesive systems depends on barrier orientation, adhesion, manipulation, defects, and storage procedures is quantified via calcium tests. Furthermore, it is found that introducing an additional adhesion‐promoting layer on the standard UHPBF stack reduces WVTRs by a factor of 5 compared to barriers without it. Finally, barriers are used for sealing and encapsulation of perovskite solar cells (PSCs) enabling the extraction of a relationship between WVTRs of barrier/adhesive systems and degradation rates (DR) of PSCs. DR fall exponentially when WVTRs decrease from 101 to 10−3 g m−2 d−1. Outside that range any gains or losses are mitigated by tailing of the sigmoid curve relating the two parameters. Results highlight important factors which will help those developing strategies relating to encapsulation, barrier, adhesive and sealant systems and stable optoelectronic devices on glass and flexible substrates.

Conservation of cultural heritage is an area where novel scientific techniques are having enormous impact. Given the value and uniqueness of art pieces, non-invasive diagnostic methods are highly appreciated by conservators. Terahertz radiation has shown enormous potential as non-contact probe that can be used for the three-dimensional reconstruction of internal structure of stone-made objects. In this article we report the evaluation of the internal damage state of two art pieces, a medallion from the Castle of Celle and a window sill from the St. Peter of Trier Cathedral. We also used terahertz radiation to follow and assess the restoration process of the window sill. We found that terahertz spectroscopy is an excellent non-destructive evaluation method for stone artwork that shows enormous potential as a tool for conservation.

Abstract Organic light-emitting diodes (OLEDs) suffer from notorious light trapping, resulting in only moderate external quantum efficiencies. Here, we report a facile, scalable, lithography-free method to generate controllable nanostructures with directional randomness and dimensional order, significantly boosting the efficiency of white OLEDs. Mechanical deformations form on the surface of poly(dimethylsiloxane) in response to compressive stress release, initialized by reactive ions etching with periodicity and depth distribution ranging from dozens of nanometers to micrometers. We demonstrate the possibility of independently tuning the average depth and the dominant periodicity. Integrating these nanostructures into a two-unit tandem white organic light-emitting diode, a maximum external quantum efficiency of 76.3% and a luminous efficacy of 95.7 lm W−1 are achieved with extracted substrate modes. The enhancement factor of 1.53 ± 0.12 at 10,000 cd m−2 is obtained. An optical model is built by considering the dipole orientation, emitting wavelength, and the dipole position on the sinusoidal nanotexture.

In recent years, both biodegradable and bio-based electronics have attracted increasing interest, but are also controversially discussed at the same time. Yet, it is not clear whether they will contribute to science and technology or whether they will disappear without major impact. The present review will address several aspects while showing the potential opportunities of bio-organic electronics. An overview about the complex terminology of this emerging field is given and test methods are presented which are used to evaluate the biodegradable properties. It will be shown that the majority of components of organic electronics can be substituted by biodegradable or bio-based materials. Moreover, application scenarios are presented where bio-organic materials have advantages compared to conventional ones. A variety of publications are highlighted which encompass typical organic devices like organic light emitting diodes, organic solar cells and organic thin film transistors as well as applications in the field of medicine or agriculture.

Inactivated vaccines are commonly produced by incubating pathogens with chemicals such as formaldehyde or β-propiolactone. This is a time-consuming process, the inactivation efficiency displays high variability and extensive downstream procedures are often required. Moreover, application of chemicals alters the antigenic components of the viruses or bacteria, resulting in reduced antibody specificity and therefore stimulation of a less effective immune response. An alternative method for inactivation of pathogens is ionizing radiation. It acts very fast and predominantly damages nucleic acids, conserving most of the antigenic structures. However, currently used irradiation technologies (mostly gamma-rays and high energy electrons) require large and complex shielding constructions to protect the environment from radioactivity or X-rays generated during the process. This excludes them from direct integration into biological production facilities. Here, low-energy electron irradiation (LEEI) is presented as an alternative inactivation method for pathogens in liquid solutions. LEEI can be used in normal laboratories, including good manufacturing practice (GMP)- or high biosafety level (BSL)-environments, as only minor shielding is necessary. We show that LEEI efficiently inactivates different viruses (influenza A (H3N8), porcine reproductive and respiratory syndrome virus (PRRSV), equine herpesvirus 1 (EHV-1)) and bacteria (Escherichia coli) and maintains their antigenicity. Moreover, LEEI-inactivated influenza A viruses elicit protective immune responses in animals, as analyzed by virus neutralization assays and viral load determination upon challenge. These results have implications for novel ways of developing and manufacturing inactivated vaccines with improved efficacy.

Abstract Optical biosensors based on plasmonic sensing schemes combine high sensitivity and selectivity with label‐free detection. However, the use of bulky optical components is still hampering the possibility of obtaining miniaturized systems required for analysis in real settings. Here, a fully miniaturized optical biosensor prototype based on plasmonic detection is demonstrated, which enables fast and multiplex sensing of analytes with high‐ and low molecular weight (80 000 and 582 Da) as quality and safety parameters for milk: a protein (lactoferrin) and an antibiotic (streptomycin). The optical sensor is based on the smart integration of: i) miniaturized organic optoelectronic devices used as light‐emitting and light‐sensing elements and ii) a functionalized nanostructured plasmonic grating for highly sensitive and specific localized surface plasmon resonance (SPR) detection. The sensor provides quantitative and linear response reaching a limit of detection of 10 −4 refractive index units once it is calibrated by standard solutions. Analyte‐specific and rapid (15 min long) immunoassay‐based detection is demonstrated for both targets. By using a custom algorithm based on principal‐component analysis, a linear dose–response curve is constructed which correlates with a limit of detection (LOD) as low as 3.7 µg mL −1 for lactoferrin, thus assessing that the miniaturized optical biosensor is well‐aligned with the chosen reference benchtop SPR method.

We report 12% efficient CdS/CdTe thin film solar cells prepared by low temperature close space sublimation (CSS). Both semiconductor films, CdS and CdTe, were deposited by high vacuum CSS in superstrate configuration on glass substrates with fluorine doped tin oxide (FTO) front contact. The CdTe deposition was carried out at a substrate temperature (Tsub) of ≤340 ∘C, which is much lower than that used in conventional processes (>500 ∘C). The CdTe films were treated with the usual CdCl2 activation process. Different optimal annealing times and temperatures were found for low-temperature cells (Tsub≤ 340 ∘C) compared to high-temperature cells (Tsub = 520 ∘C). The influence of the activation step on the morphology of high-temperature and low-temperature CdTe is determined by XRD, AFM, SEM top views, and SEM cross-sections. Grain growth, strong recrystallization, and a reduction of planar defects during the activation step are observed, especially for low-temperature CdTe. Further, the influence of CdS deposition parameters on the solar cell performance is investigated by using three different sets of parameters with different deposition rates and substrate temperatures for the CdS preparation. Efficiencies about 10.9% with a copper-free back contact and 12.0% with a copper-containing back contact were achieved using the low temperature CdTe process.

A system for continuous monitoring of atmospheric corrosivity has been developed. An electronic unit measures and records changes in the electrical resistance of a thin metal track applied on an insulating substrate. If the metal corrodes, the effective cross sectional area of the track decreases and the electrical resistance increases. Sensors made of silver, copper, iron/steel, zinc, lead, tin, aluminium, bronze, and brass at thicknesses from 50 nm to 250 µm were tailored for environments with different corrosivities. The developed technology proved capable of providing high sensitivity, allowing for real-time corrosion monitoring even in low-corrosive indoor cultural heritage facilities. Laboratory tests showed good reproducibility with the standard deviation of parallel measurements at less than ±20% for metals which corrode uniformly in the tested environments. Several examples selected from a broad testing programme in partner museums, libraries, and other institutions show successful applications of the logger system for characterization of air quality control in indoor locations, during transport and in temporary exhibitions; assessment of new buildings and storage facilities; and fundamental studies of optimal conservation and storage procedures. A first outline of a classification system for lead, which is particularly sensitive to the presence of carboxylic acids, is given. The technique has a large potential as an independent method for monitoring air quality in facilities displaying and storing valuable objects of cultural heritage.

Organic conducting polymers are promising electrode materials for printable organic electronics. One of the most studied conducting polymers is PEDOT: PSS, which is sufficiently conductive and transparent, but which shows some drawbacks, such as hygroscopicity and acidity. A new approach to stabilize PEDOT in aqueous dispersions involves the replacement of PSS with a basic polyanion based on a polystyrene backbone with (trifluoromethylsulfonyl)imide (TSFI) side groups. The PEDOT: PSTFSIK dispersions were obtained by oxidative polymerization of EDOT in an aqueous PSTFSIK solution and were characterized with regard to their composition, morphology, doping, rheological behavior, and optoelectronic performance. The PEDOT: PSTFSIK dispersions showed excellent printability and good optoelectronic performance (238 Ohm sq(-1) at 91% transmittance, σ>260 S cm(-1)) and were successfully integrated as flexible electrodes in OLED and OPV devices.