Search

Monolithic all-perovskite tandem photovoltaics promise to combine low-cost and high-efficiency solar energy harvesting with the advantages of all-thin-film technologies. To date, laboratory-scale all-perovskite tandem solar cells have only been fabricated using non-scalable fabrication techniques. In response, this work reports on laser-scribed all-perovskite tandem modules processed exclusively with scalable fabrication methods (blade coating and vacuum deposition), demonstrating power conversion efficiencies up to 19.1% (aperture area, 12.25 cm2; geometric fill factor, 94.7%) and stable power output. Compared to the performance of our spin-coated reference tandem solar cells (efficiency, 23.5%; area, 0.1 cm2), our prototypes demonstrate substantial advances in the technological readiness of all-perovskite tandem photovoltaics. By means of electroluminescence imaging and laser-beam-induced current mapping, we demonstrate the homogeneous current collection in both subcells over the entire module area, which explains low losses (rel) in open-circuit voltage and fill factor for our scalable modules.

Given the outstanding progress in research over the past decade, perovskite photovoltaics (PV) is about to step up from laboratory prototypes to commercial products. For this to happen, realizing scalable processes to allow the technology to transition from solar cells to modules is pivotal. This work presents all-evaporated perovskite PV modules with all thin films coated by established vacuum deposition processes. A common 532-nm nanosecond laser source is employed to realize all three interconnection lines of the solar modules. The resulting module interconnections exhibit low series resistance and a small total lateral extension down to 160 μm. In comparison with interconnection fabrication approaches utilizing multiple scribing tools, the process complexity is reduced while the obtained geometrical fill factor of 96% is comparable with established inorganic thin-film PV technologies. The all-evaporated perovskite minimodules demonstrate power conversion efficiencies of 18.0% and 16.6% on aperture areas of 4 and 51 cm$^{2}$, respectively. Most importantly, the all-evaporated minimodules exhibit only minimal upscaling losses as low as 3.1%$_{rei}$ per decade of upscaled area, at the same time being the most efficient perovskite PV minimodules based on an all-evaporated layer stack sequence.

Monolithic two-terminal (2T) perovskite/CuInSe$_2$ (CIS) tandem solar cells (TSCs) combine the promise of an efficient tandem photovoltaic (PV) technology with the simplicity of an all-thin-film device architecture that is compatible with flexible and lightweight PV. In this work, we present the first-ever 2T perovskite/CIS TSC with a power conversion efficiency (PCE) approaching 25% (23.5% certified, area 0.5 cm$^2$). The relatively planar surface profile and narrow band gap (∼1.03 eV) of our CIS bottom cell allow us to exploit the optoelectronic properties and photostability of a low-Br-containing perovskite top cell as revealed by advanced characterization techniques. Current matching was attained by proper tuning of the thickness and bandgap of the perovskite, along with the optimization of an antireflective coating for improved light in-coupling. Our study sets the baseline for fabricating efficient perovskite/CIS TSCs, paving the way for future developments that might push the efficiencies to over 30%.

Lightweight potential is a powerful indicator – but not as powerful as it could be. Current methods for analyzing a product's potential to be reduced in mass only deal with a few of the most important criteria for lightweight design. This paper presents an approach transferring cost-benefit analysis to the holistic derivation of lightweight potential. The approach is able to deal with different types of criteria supporting the designer in indentifying the most promising components for mass reduction. An evaluation example is given showcasing a tooling machine.

Vacuum-assisted growth (VAG) control is one of the most promising methods for controlling nucleation and crystallization of printed and coated large area lead halide perovskite-based layers for optoelectronics. To coat or print homogeneous high-quality perovskite thin-films at high fabrication yield, real-time process monitoring of the VAG is pivotal. In response, a 2.1-megapixel multichannel photoluminescence (PL) and reflection imaging system is developed and employed for the simultaneous spatial in situ analysis of drying, nucleation, and crystal growth during VAG and subsequent thermal annealing of inkjet-printed and blade-coated perovskite thin-films. It is shown that the VAG process, for example, evacuation rate and time, affects the film formation and provide detailed insight into traced PL and reflection transients extracted from sub-second videos of each channel. Based on correlative analysis between the transients and, for example, perovskite ink composition, wet-film thickness, or evacuation time, key regions which influence crystal quality, film morphology, and are base for prediction of solar cell performance are identified.

To scale up production of perovskite photovoltaics, state-of-the-art laboratory recipes and processes must be transferred to large-area coating and drying systems. The development of in situ monitoring methods that provide real-time feedback for process control is pivotal to overcome this challenge. Herein, correlative in situ multichannel imaging (IMI) obtaining reflectance, photoluminescence intensity, and central photoluminescence emission wavelength images on areas larger than 100 cm2 with subsecond temporal resolution using a simple, cost-effective setup is demonstrated. Installed on top of a drying channel with controllable laminar air flow and substrate temperature, IMI is shown to consistently monitor solution film drying, perovskite nucleation, and perovskite crystallization. If the processing parameters differ, IMI reveals characteristic changes in large-area perovskite formation dynamics already before the final annealing step. Moreover, when IMI is used to study >130 blade-coated devices processed at the same parameters, about 90% of low-performing devices contain coating inhomogeneities detected by IMI. The results demonstrate that IMI should be of value for real-time 2D monitoring and feedback control in industrial-scale, high-throughput fabrication such as roll-to-roll printing.

Perovskite/silicon tandem photovoltaics have attracted enormous attention in science and technology over recent years. In order to improve the performance and stability of the technology, new materials and processes need to be investigated. However, the established sequential layer deposition methods severely limit the choice of materials and accessible device architectures. In response, a novel lamination process that increases the degree of freedom in processing the top perovskite solar cell (PSC) is proposed. The very first prototypes of laminated monolithic perovskite/silicon tandem solar cells with stable power output efficiencies of up to 20.0% are presented. Moreover, laminated single-junction PSCs are on par with standard sequential layer deposition processed devices in the same architecture. The numerous advantages of the lamination process are highlighted, in particular the opportunities to engineer the perovskite morphology, which leads to a reduction of non-radiative recombination losses and and an enhancement in open-circuit voltage (Voc). Laminated PSCs exhibit improved stability by retaining their initial efficiency after 1-year aging and show good thermal stability under prolonged illumination at 80 °C. This lamination approach enables the research of new architectures for perovskite-based photovoltaics and paves a new route for processing monolithic tandem solar cells even with a scalable lamination process.

In this paper, we present a method to obtain explicit, expressive and interpretable gait feature signals from an inertial sensor, mounted on any segment of the lower limbs. The proposed method is invariant to the mounting orientation of the sensor, works without magnetometer information, requires no prior knowledge and can be used in real-time scenarios. Moreover, the constructed signals are robust for a wide variety of changing walking speeds and directions. We investigate the informational content of our three feature signals lying in the human sagittal plane with respect to the gait phase segmentation problem and compare them to other commonly used signals, such as the sagittal angular velocity and the norms of accelerations and angular velocities. To this end, we make use of the filter-based maximum relevance minimum redundancy algorithm, which is a classifier-independent feature selection method. For validating our approach, we consider gait data of twelve healthy subjects walking straight and in curves at self-chosen speeds with inertial sensors attached to either the thigh, shank or foot. Additionally, pressure measuring insoles are used to obtain ground truth toe-off and heel-strike gait events for reference. With those events as the gait phase transitions, the event detection is cast into a classification problem. To support the theoretical findings of the feature selection and ranking, we finally evaluate different choices of feature sets with a simple linear support vector machine classifier in an online fashion and obtain superior segmentation results with our feature signals.

Lightweight potential is a powerful indicator – but not as powerful as it could be. Current methods for analyzing a product's potential to be reduced in mass only deal with a few of the most important criteria for lightweight design. The amount of literature dealing with lightweight design is significant, yet it can help to understand these versatile criteria. Firstly, the literature on this topic will therefore be reviewed to derive a broad set of criteria used in contemporary lightweight design. Secondly, a further review will reveal the criteria used to derive lightweight potential. Subsequently, both sets will be compared to identify the missing criteria used for the derivation of lightweight potential. This will support designers in two ways. On the one hand, matching and combining both criteria sets will enable the most representative criteria for a particular design case to be chosen, thus leading to a more comprehensible derivation of lightweight potential. On the other hand, the combination set will provide a basis for designers and design teams to refine their understanding of their own motivations for conducting lightweight design.

For the upscaling of hybrid perovskite photovoltaics, the understanding of the intermediate steps from solution to the polycrystalline film is pivotal. In situ characterization techniques can be a powerful tool to investigate the perovskite formation process and obtain direct feedback on its quality. Here, we propose in situ photoluminescence intensity, photoluminescence emission wavelength and reflectance imaging combined in one optical system with a high spatial and sub-second temporal resolution as an in situ real-time, monitoring technique. It is capable of surveilling the perovskite processing on areas larger 100 cm2 and resolving even tiny differences in the processing parameters.

Lightweight-design methods for the early phases of the product-development process are becoming increasingly important due to their significant influence on the products’ mass. Besides mass reduction, the redistribution of mass within a product can help to achieve lightweight-design targets much more effectively. The aim of this paper is to raise awareness of lightweight-design tasks during the conceptual phase, in which the distribution of mass constitutes a significant element of the designers’ work. Due to the fact that mass distribution always affects the structure of a product, the authors link the lightweight-design tasks investigated to product architecture design in the conceptual phase. This enables different methods to be identified which can support the designer in achieving the lightweight-design task through mass distribution.

Inhalt: Die Fräskanttechnik stellt ein Fertigungsverfahren dar, um aus plattenförmigen Materialien räumliche Strukturen auf einfache Weise herzustellen. In diesem Beitrag werden die praxisnahe Anwendbarkeit dieser Technik für ein Aluminiumschaum-Sandwich am Beispiel der Konstruktion und Herstellung eines Trägers aufgezeigt und für dieses Bauteil Gestaltungsregeln abgeleitet.

Lightweight-design methods for the conceptual phase of the product-development process are becoming increasingly important due to their influence on products’ mass. Besides mass reduction, the redistribution of mass within the product can support the designer in addressing lightweight-design motivations more effectively. This paper introduces a method of systematic mass distribution using the design structure matrix (DSM). A case study of a high-pressure water-jetting unit serves as an application example to illustrate the procedure introduced.

Thermal images generated from infrared radiation are useful for monitoring many processes; however, infrared cameras are orders of magnitude more expensive than their visible counterparts. Methods that allow visible cameras to capture thermal images are therefore of interest. In this contribution, thermal images of a surface coated with an inexpensive inorganic micropowder phosphor are generated from the analysis of a video taken with a smartphone camera. The phosphor is designed to have a temperature‐dependent emission lifetime that is long enough to be determined from the analysis of a 30 frames‐per‐second video recording. This proof‐of‐principle work allows temperatures in the 270–320 K range to be accurately determined with a precision better than 2 K, even in the presence of bright background illuminance up to 1500 lm m$^{-2}$. In the broader context, this inspires further development of phosphors to bring time‐resolved sensing techniques into lifetime long enough ranges to allow smartphone‐based detection.

Lightweight design methods help the engineer to design lighter products. However, none of the existing methods support lightweight design with regard to the state of motion of mass and the mass distribution. This paper presents an analytic method to fill this gap. The method uses kinetic and potential energies to determine an energy level factor. This factor enables the engineer to derive an optimization potential and order of all different product assemblies. Finally, a case study is performed on a processing machine to illustrate the effectiveness of the developed method.