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We investigated a self-organization process leading to a hyperuniform structure for light trapping in silicon-based tandem solar cells. EQE measurements showed similar results with this bottom-up process as for the structures realized via NIL.

Background Assessing the residual cancer burden (RCB) predictive performance, the potential subgroup effects, and time-dependent impact on breast cancer patients who underwent neoadjuvant therapy in a developer’s independent cohort is essential for its usage in clinical routine. Methods Between 2011 and 2016, the RCB scores of 184 female breast cancer patients were prospectively collected, and subsequent clinicopathological and follow-up data were obtained retrospectively. Recurrence-free survival (RFS), overall survival (OS), as well as subgroup analysis, and time-dependent variables were calculated with multivariate, complex, or linear statistical models. Results A total of 184 patients (HER2 33%, TNBC 27%), with a mean follow-up time of 4 years, treated with neoadjuvant systemic therapy (92% anthracycline-taxane based) were analyzed revealing 43 events (38 recurrences, 28 deaths). High RCB scores were associated with recurrence (median index: 2.34 vs. 1.39 points, rank-sum p

Background: The prognostic performance of the residual cancer burden (RCB) score is a promising tool for breast cancer patients undergoing neoadjuvant therapy. We independently evaluated the prognostic value of RCB scores in an extended validation cohort. Additionally, we analyzed the association between chemotherapy dose reduction and RCB scores. Methods: In this extended validation study, 367 breast cancer patients with available RCB scores were followed up for recurrence-free survival (RFS), distant disease-free survival (DDFS), and overall survival (OS). We also computed standardized cumulative doses of anthracyclines and taxanes (A/Ts) to investigate a potential interaction between neoadjuvant chemotherapy dose reduction and RCB scores. Results: Higher RCB scores were consistently associated with adverse clinical outcomes across different molecular subtypes (HR for RFS = 1.60, 95% CI 1.33–1.93, p &lt, 0.0001, HR for DDFS = 1.70, 95% CI 1.39–2.05, p &lt, HR for OS = 1.67, 95% CI 1.34–2.08, p &lt, 0.0001). The adverse impact prevailed throughout 5 years of follow-up, with a peak for relapse risk between 1–2 years after surgery. Clinical outcomes of patients with RCB class 1 did not differ substantially at 5 years compared to RCB class 0. A total of 180 patients (49.1%) underwent dose reduction of neoadjuvant A/T chemotherapy. We observed a statistically significant interaction between dose reduction and higher RCB scores (interaction p-value = 0.042). Conclusion: Our results confirm RCB score as a prognostic marker for RFS, DDFS, and OS independent of the molecular subtype. Importantly, we show that lower doses of cumulative neoadjuvant A/T were associated with higher RCB scores in patients who required a dose reduction.

III-V/Si tandem solar cells are investigated as a promising solution to increase the power output of photovoltaic modules under terrestrial sunlight conditions. Over the last years, we have developed a wafer-bonded GaInP/AlGaAs//Si triple-junction solar cell with a recently calibrated conversion efficiency of 34.1% under AM1.5g. This is the highest efficiency of any Si-based 2-terminal tandem device and it shows the potential of this technology to reach significantly higher performances than any single-junction devices.

By adjusting the process flow of a newly developed transparent conductive adhesive (TCA), the first mechanically stable interconnection of a glued III-V on Si tandem solar cell was established utilizing a ZnO-based adhesive. The measured $V_{OC}$ of 1691 mV is a first proof of concept for the developed TCA. The functionality of the two sub-cells in the tandem device was proven by external quantum efficiency (EQE) measurements. The reflectance at the bond interface of such a glued tandem solar cell remains the limiting factor. In order to reduce the optical losses, the effect of a textured silicon surface was investigated in test structures, which indeed showed reduced reflectance. Furthermore, this textured test structure showed an improved connecting resistivity as low as $83\ \mathrm{m}\Omega\text{cm}^{2}$ .

Perovskite silicon tandem solar cells can exceed the efficiency limit of 29.4% of single junction silicon solar cells, with comparably low additional costs for depositing the layers for the perovskite solar cell. Hence, they are an attractive option to further decrease the costs of photovoltaic electricity generation. We present, how by optimizing perovskite absorber composition, choosing adequate carrier selective contact layers, introducing surface passivation and optimizing the individual layer thicknesses solar cell efficiencies above 25% can be realized experimentally. Furthermore, we discuss different options for reducing front surface reflection by anti-reflection coatings, structured foils and deposition on textured silicon wafers and their impact both on solar cell efficiency as well as on the yearly energy yield. Deposition on textured silicon wafers promises highest energy yield. Hence, we show how perovskite absorbers can be deposited on such substrates by either co-evaporation or hybrid processing combining evaporation and subsequent wet-chemical processing. By bottom up cost calculations we finally show how and under which conditions perovskite silicon tandem solar cells can yield an economic advantage.

Single-junction Si solar cell efficiencies are intrinsically limited to 29.4%. One common strategy to overcome this fundamental issue is to combine multiple semiconductor materials with different bandgaps in a multi-junction configuration so that light is effectively absorbed over a broad range in the solar spectrum. In particular, the combination of a III-V top cell (GaInP/GaAs) that is wafer-bonded to a planar Si bottom cell led recently to an overall record efficiency of 34.1%. The efficiency of this tandem design could be further improved if absorption in the Si cell near the bandgap (1000-1200 nm) is enhanced. Here, we present a nanostructured metallodielectric back reflector placed at the rear of the Si cell that selectively steers incoming light to angles outside the escape cone of the tandem cell. The design is composed of a hexagonal array of Ag nanodisks embedded in a PMMA layer at the rear of the Si cell. Using finite-difference time-domain simulations we optimize pitch, radius, and height of the individual Ag scatterer such that we evenly distribute scattered power over the different diffraction orders. We analyze the scattering behavior in terms of plasmon scattering by the Ag disks and Mie scattering in the dielectric PMMA inclusions. To fully optimize light trapping inside the cell, we choose the geometry such that both 0th-order reflection and plasmonic losses in the Ag nanodisks are minimized. We experimentally demonstrate photonic light trapping by fabricating large scale (2.5×2.5 cm) nanopatterns on untextured Si solar cells. Large-area patterning is performed via Substrate Conformal Imprint Lithography (SCIL) using silica sol-gel as a mask to etch patterns in PMMA, followed by thermal evaporation of Ag. Cross-section SEM shows excellent conformal deposition of Ag inside the patterned nanoholes. Light scattering spectroscopy shows a clearly reduced reflection of the Si cell in the desired wavelength range (1000-1200 nm) due to light trapping, in agreement with simulations. Experimental data of the full nanopatterned III-V/Si tandem geometry will be shown.

Upconversion of low-energy photons into higher energy photons is a non-linear effect that can be strongly enhanced by increasing the intensity of impinging light. Such an enhanced intensity can also be achieved by near-field optical effects in photonic structures. In this paper, we investigate photonic structures in the form of linear gratings with varying periods realised in poly-methyl-methacrylate (PMMA) layers using soft stamps in a thermal nanoimprint process. Master structures were fabricated using e-beam lithography and reactive ion etching in silicon. These master structures were replicated into bi-layer polydimethylsiloxane (PDMS) stamps. PMMA layers with embedded β-NaYF4:25% Er3 + upconverter nanoparticles were applied to glass substrates using spin coating. The PDMS stamps were used to imprint the PMMA layer with very accurate pattern fidelity. The upconversion luminescence around 980 nm was enhanced more than three times by the photonic structure under 1523 nm laser excitation with 0.43 ± 0.02 W/cm2 irradiance, in comparison to a reference sample containing the same amount of upconverter material.

Silicon solar cells featuring the highest conversion efficiencies are made from monocrystalline n-type silicon. The superior crystal quality of high-performance multicrystalline silicon (HP mc) in combination with the inherent benefits of n-type doping (higher tolerance to common impurities) should allow the fabrication of high-efficiency solar cells also on mc silicon. In this paper, we address high-efficiency n-type HP mc solar cells with diffused boron front emitter and full-area passivating rear contact (TOPCon). n-type HP mc silicon was crystallized at Fraunhofer ISE featuring a very high average lifetime in the range of 600 μ s (i.e., diffusion length >800 μ m) after application of all high-temperature steps necessary for cell fabrication. Using a “black silicon” front texture we have achieved a weighted reflectance of ∼1% and simultaneously a very good electrical performance, i.e., J 0 e values of ≤ 60 fA/cm2 for a 90 Ω/sq emitter. The resulting n-type mc silicon solar cells show certified conversion efficiencies up to 21.9%, representing the current world record for mc silicon solar cells.

Honeycomb textures provide excellent reflectance reduction for multicrystalline silicon solar cells. Achieved reflectance levels are comparable or even superior to those of pyramidal textures for monocrystalline silicon. Honeycombs were used to achieve record efficiencies for multicrystalline silicon solar cells. In this paper, we present an analytical optical model for the calculation of the front surface reflectance of honeycomb-textured silicon wafer solar cells in air environment and in a module. Reflectance is calculated using an analytical path tracer for a geometric representation of the texture's symmetry. Light trapping in the module is calculated using a retro-reflection model. We evaluate the approach for a selected set bare and antireflection-coated samples against air and for encapsulated samples. For the used samples, we show that as little as 1% of the net incoming photons are reflected at the solar cell–air interface. Compared with state-of-the-art isotextures, the presented honeycomb textures reduce the net reflectance loss in a photovoltaic (PV) module from 0.8 to 0.3 mA/cm2 .

This work presents the results of the electrical and optical characterization of a new transparent conductive adhesive (TCA) that combines the techniques of spray pyrolysis and a sol-gel like process. This approach is of particular interest since the adhesive itself forms both the electrical and the mechanical interconnection of the bonded sub-cells. The electrical and optical characterization of the developed TCA shows a minimum connecting resistivity of 17 Ωcm2 and a simulated reflection at the Si-TCA interface of ≈ 20%. By coating both substrate surfaces with a TiO2 anti reflection coating (ARC), the reflectance at the Si-TCA interface was successfully reduced down to 80% of maximum), while additionally reducing the connecting resistivity to 10 Ωcm² or 1 Ωcm2 allows for a further increase to 27.3% and 30.0%, respectively.

Silicon solar cells are typically textured by means of wet chemical etching in order to enhance absorption. Within this work, we apply an optically functional layer onto a planar silicon surface. This layer is made of a high refractive index sol-gel material and can be patterned by nanoimprint lithography (NIL). In first experiments, we investigated various sol-gel based TiO2 precursors and evaluated their refractive index as well as the possibility to apply them in NIL. The refractive index was determined to be up to 2.25 using ellipsometry. This result was achieved with a solution composed of amorphous TiO2 precursors mixed with ethanol and 1,5-pentanediol. The topography of the patterned TiO2 layers were investigated using an atomic force microscope (AFM) and a scanning electron microscope (SEM) revealing a period of 1 μm and a pattern depth of 60 nm after sintering. Furthermore, optical modeling was used to optimize the structure parameters in order to minimize the weighted reflectance of an encapsulated silicon solar cell.

Silicon dominates the photovoltaic industry but the conversion efficiency of silicon single-junction solar cells is intrinsically constrained to 29.4%, and practically limited to around 27%. It is possible to overcome this limit by combining silicon with high-bandgap materials, such as III–V semiconductors, in a multi-junction device. Significant challenges associated with this material combination have hindered the development of highly efficient III–V/Si solar cells. Here, we demonstrate a III–V/Si cell reaching similar performances to standard III–V/Ge triple-junction solar cells. This device is fabricated using wafer bonding to permanently join a GaInP/GaAs top cell with a silicon bottom cell. The key issues of III–V/Si interface recombination and silicon's weak absorption are addressed using poly-silicon/SiOx passivating contacts and a novel rear-side diffraction grating for the silicon bottom cell. With these combined features, we demonstrate a two-terminal GaInP/GaAs//Si solar cell reaching a 1-sun AM1.5G conversion efficiency of 33.3%. As silicon solar cells are reaching their optimal efficiencies, below 30%, multi-junctions are being developed to increase the electrical power output over the same area. Here, Cariou et al. use wafer-bonding to fabricate two-terminal silicon III–V tandem cells that reach efficiencies above 33%.

In this paper, large-area honeycomb (HC) texturing of multi-crystalline Si substrates with a newly developed process chain based on roller nanoimprint lithography and inline-capable plasma etching is demonstrated. The realized HC-textures show optical properties superior to random pyramids on c-Si, while the surface passivation quality is comparable. First, results on 156 × 156 mm2 multi-crystalline Si solar cells with an aluminum back-surface field show an efficiency of η = 17.8% compared with η = 17.3% on isotextured reference samples. This efficiency gain of 0.5% results from an increase in $J_{{\rm sc}}$ of up to 1.3 mA/cm2, which underlines the high optical and electrical quality of the texture. On a smaller area (50 × 50 mm2), the gain in $J_{{\rm sc}}$ of HC-textured cells compared with isotextured references was even higher with up to 2.5 mA/cm2.

Silicon based multi-junction solar cells are a promising option to overcome the theoretical efficiency limit of a silicon solar cell (29.4%). With III-V semiconductors, high bandgap materials applicable for top cells are available. For the application of such silicon based multi-junction devices, a full integration of all solar cell layers in one 2-terminal device is of great advantage. We realized a triple-junction device by wafer-bonding two III-V-based top cells onto the silicon bottom cell. However, in such a series connected solar cell system, the currents of all sub-cells need to be matched in order to achieve highest efficiencies. To fulfil the current matching condition and maximise the power output, photonic structures were investigated. The reference system without photonic structures, a triple-junction cell with identical GaInP/GaAs top cells, suffered from a current limitation by the weakly absorbing indirect semiconductor silicon bottom cell. Therefore rear side diffraction gratings manufactured by nanoimprint lithography were implemented to trap the infrared light and boost the solar cell current by more than 1 mA/cm2. Since planar passivated surfaces with an additional photonic structure (i.e. electrically planar but optically structured) were used, the optical gain could be realized without deterioration of the electrical cell properties, leading to a strong efficiency increase of 1.9% absolute. With this technology, an efficiency of 33.3% could be achieved.

Reflectance, reduction, and light trapping enhancement are essential to maximize the absorption of silicon solar cells. The industrial state of the art method to improve the solar cell optics is wet chemical texturization of the front surface in combination with the deposition of antireflection coatings. This work analyzes an alternative route, namely a TiO2 pillar structure on the front side of a planar silicon solar cell encapsulated in ethylene vinyl acetate (EVA) and glass. It focuses on parameter variations of the structured TiO2 layer while taking the module encapsulation into account. It is shown that internal reflections at the front interface of the module play a crucial role for the structure design. This leads to optimized structures working in a different optical regime. While state of the art structures optimized for a half infinite encapsulation act as effective media, structures optimized for the full module show an improved performance by making use of diffractive effects. It could be shown that weighted reflectance of 4.7% can be reached for a solar module with TiO2 pillar structure on top of the silicon surface compared to 5.5% for a two-layer ARC with a TiO2 bottom layer and 2.3% for an isotexture, which is the state of the art structure for multicrystalline silicon cells.

Micro- and nanostructures can be used for reflectance reduction or light guidance in applications like photovoltaic solar cells, LEDs or display technology. The combination of interference lithography and nanoimprint lithography enables the fabrication and replication of high resolution structures on large areas. The origination of master structures, seamlessly patterned on areas as large as 1.2 × 1.2 m2 was shown using interference lithography. Within this work we demonstrate our current results on the up-scaling of the replication process chain based on nanoimprint lithography with in-line capable tools. Application examples in the fields of photovoltaics are demonstrated, e.g. the micron-scale patterning of multicrystalline silicon substrates to increase the solar cell efficiency. Furthermore, the lifetime of soft PDMS stamps is investigated. AFM force-distance measurements are introduced as suitable method to quantify the PDMS hardness as a parameter indicating stamp degradation. This technique is subsequently applied to evaluate two different resist materials. Applying the epoxy material (SU-8) with its more complex molecular structure results in a strongly increased stamp lifetime compared to the acrylate resist (Laromer LR 8996). This is a highly valuable result for further developments towards an up-scaled realization of nanoimprint lithography.

A comprehensive analysis of the optical properties of different surface textures for silicon solar cells must include (i) the optical performance at cell level as well as encapsulated to a module stack and (ii) a varying angle of incidence of the solar irradiation, as it influences the optical yield. Within this work, the OPTOS formalism (Optical Properties of Textured Optical Sheets) was used to compare a honeycomb texture featuring a high aspect ratio with state of the art random pyramids and the isotexture. The honeycomb texture exhibits an increased absorbed photocurrent density of 2.3 mA/cm 2 before and 0.7 mA/cm 2 after encapsulation compared to the isotexture for a 180 µm thick solar cell. The simulated absolute value of 42.3 mA/cm 2 after encapsulation is even superior to the random pyramid texture with 41.5 mA/cm 2 . Furthermore, a simulation-based optical yield analysis reveals that the angular irradiance of three exemplary terrestrial locations plays a minor role for the relative performance between the textures compared to influence of encapsulation effects.

Within this work we investigate the lifetime of soft PDMS stamps as a critical parameter for the up-scaled fabrication of microstructures via nanoimprint lithography. We propose the characterization of the PDMS hardness as a suitable parameter for the stamp degradation. The increasing hardness for a larger number of imprints is attributed to resist diffusion into the PDMS volume and possibly subsequent cross-linking. Force-distance measurements with an atomic force microscope were applied to demonstrate for two acrylic materials that a lower average molecular weight leads to a faster degradation. Using a temperature-assisted UV-imprint process with an epoxy material (SU-8 2002) enabled more than 100 imprints without measurable degradation due to the complex molecular structure which we assume to reduce the resist diffusion. This can be a key development towards a higher stamp lifetime and finally an industrial realization of NIL.

We show that the radiation-hardness of space solar cells can be significantly improved by employing nanophotonic light trapping. Two light-trapping structures are investigated in this work. In the first, an array of Al nanoparticles is embedded within the anti-reflection coating of a GaInP/InGaAs/Ge solar cell. A combined experimental and simulation study shows that this structure is unlikely to lead to an improvement in radiation hardness. In the second, a diffractive structure is positioned between the middle cell and the bottom cell. Computational results, obtained using an experimentally validated electro-optical simulation tool, show that a properly designed light-trapping structure in this position can lead to a relative 10% improvement in the middle-cell photocurrent at end-of-life.

After more than 20 years of research on rear side gratings for light trapping in solar cells, we have been able to demonstrate enhanced efficiencies for crystalline silicon solar cells with two different grating concepts and solar cell architectures. In both cases planar front sides have been used. With hexagonal sphere gratings and the tunnel oxide passivated contact (TOPCon) concept, a grating induced Jsc increase of 1.4 mA/cm2 and an efficiency increase of 0.8%absolute could be achieved. With binary crossed gratings fabricated by a nanoimprint based process chain, a grating induced Jsc gain of 1.2 mA/cm2 and an efficiency gain of 0.7% absolute could be achieved. For the binary grating concept, cell thickness variations have also been performed. The increasing importance of the light trapping properties towards low solar cell thicknesses could be confirmed by an enhanced EQE in the long wavelength region (Jsc increase: 1.6 mA/cm2 for 150 μm and 1.8 mA/cm2 for 100 μm thick solar cells). The results are in very good agreement with simulations using the OPTOS modeling formalism. OPTOS enables the further analysis and optimization of grating concepts in silicon solar cells and modules. So a grating induced Jsc gain of 0.8 mA/cm2 is forecast for solar cells with pyramidal front side texture. On module level, still a grating induced Jsc gain of 0.6 mA/cm2 can be expected.

Surface textures can significantly improve anti-reflective and light trapping properties of silicon solar cells. Combining standard pyramidal front side textures with scattering or diffractive rear side textures has the potential to further increase the light path length inside the silicon and thereby increase the solar cell efficiency. In this work we introduce the OPTOS (Optical Properties of Textured Optical Sheets) simulation formalism and apply it to the modelling of silicon solar cells with different surface textures at front and rear side. OPTOS is a matrix-based method that allows for the computationally-efficient calculation of non-coherent light propagation within textured solar cells, featuring multiple textures that may operate in different optical regimes. After calculating redistribution matrices for each individual surface texture with the most appropriate technique, optical properties like angle dependent reflectance, transmittance or absorptance can be determined via matrix multiplications. Using OPTOS, we demonstrate for example that the integration of a diffractive grating at the rear side of solar cells with random pyramids at the front results in an absorptance gain that corresponds to a photocurrent density enhancement of 0.73 mA/cm 2 for a 250 μm thick cell. The re-usability of matrices enables the investigation of different solar cell thicknesses within minutes. For thicknesses down to 50 μm the simulated gain increases up to 1.22 mA/cm 2 . The OPTOS formalism is furthermore not restricted with respect to the number of textured interfaces. By combining two or more textured sheets to effective interfaces, it is possible to optically model a complete photovoltaic module including EVA and potentially textured glass layers with one calculation tool.

We investigate the integration of Al nanoparticle arrays into the anti-reflection coatings (ARCs) of commercial triple-junction GaInP/ In0.01GaAs /Ge space solar cells, and study their effect on the radiation-hardness. It is postulated that the presence of nanoparticle arrays can improve the radiation-hardness of space solar cells by scattering incident photons obliquely into the device, causing charger carriers to be photogenerated closer to the junction, and hence improving the carrier collection efficiency in the irradiation-damaged subcells. The Al nanoparticle arrays were successfully embedded in the ARCs, over large areas, using nanoimprint lithography: a replication technique with the potential for high throughput and low cost. Irradiation testing showed that the presence of the nanoparticles did not improve the radiation-hardness of the solar cells, so the investigated structure has proven not to be ideal in this context. Nonetheless, this paper reports on the details and results of the nanofabrication to inform about future integration of alternative light-scattering structures into multi-junction solar cells or other optoelectronic devices.

Many markets require large area surface relief micro- and nanostructures. Important examples are light management structures for display applications or the radiation power management in solar systems. Structuring techniques with both up-scaling and mass production potential are an essential precondition for their realization. Interference lithography is a promising technique to originate fine-tailored structures on areas of up to 1.2 x 1.2 m(2). Subsequent replication techniques have the potential for enabling an industrial fabrication. After a description of the basic technologies, we present application examples of large area structures used as template for polarization optical films. Furthermore, light trapping structures for crystalline silicon solar cells are shown. For this application, etching masks were fabricated by nanoirnprint lithography. A subsequent etching step was applied to transfer the structures into the silicon. Finally, 3-dimensional photonic structures with distinguished optical properties are presented.

Haemorrhoidal disease belongs to the most common benign disorders in the lower gastrointestinal tract. Treatment options comprise conservative as well as surgical therapy still being applied arbitrarily in accordance with the surgeon's expertise. The aim of this consensus statement was therefore to assess a stage-dependent approach for treatment of haemorrhoidal disease to derive evidence-based recommendations for clinical routine. The most common methods are discussed with respect of haemorrhoidal disease in extraordinary conditions like pregnancy or inflammatory bowel disease and recurrent haemorrhoids. Tailored haemorrhoidectomy is preferable for individualized treatment with regard to the shortcomings of the traditional Goligher classification in solitary or circular haemorrhoidal prolapses.

In this paper, we present guidelines for the design of backside gratings for crystalline silicon solar cells. We use a specially developed method based on a combination of rigorous 3D wave optical simulations and detailed semiconductor device modeling. We also present experimental results of fabricated structures. Simulation-based optimizations of grating period Λ and depth d of a binary grating and calculations of the optical and electrical characteristics of solar cells with optimized gratings are shown. The investigated solar cell setup features a thickness of dbulk = 40 µm and a flat front surface. For this setup, we show a maximum increase in short-circuit current density of ΔjSC = 1.8 mA/cm² corresponding to an efficiency enhancement of 1% absolute. Furthermore, we investigate different loss mechanisms: (i) an increased rear surface recombination velocity S0,b because of an altered surface caused by the introduction of the grating and (ii) absorption in the aluminum backside reflector. We analyze the trade-off point between gain due to improved optical properties and loss due to corrupted electrical properties. We find that, increasing the efficiency by 1% absolute due to improved light trapping, the maximum tolerable recombination velocity is S0,b(max) = 5.2 × 103 cm/s. From simulations and measurements, we conclude that structuring of the aluminum backside reflector should be avoided because of parasitic absorption. Adding a dielectric buffer layer between silicon and the structured aluminum, absorption losses can be tuned. We find that for a planar reflector, the thickness of a SiO2 buffer layer should exceed dSiO2 = 120 nm. Copyright © 2011 John Wiley & Sons, Ltd.

Since micro- and nanostructures for photon management are of increasing importance in novel high efficiency solar cell concepts, structuring techniques with up-scaling potential play a key role for the realization of these concepts. Interference lithography is reviewed as a technology for the origination of fine-tailored two and three dimensional photonic structures on large areas. With the interference pattern of two or more coherent waves, a wide variety of structures can be generated on areas of up to 1.2 x 1.2 m 2 . In combination with subsequent microreplication steps, the industrially feasible production of elaborate structures is possible. After the review of the basic technology, three novel application examples are presented: (1) honeycomb structures for the front side texturization via nanoimprint lithography, (2) diffractive back side gratings for absorption enhancement in the spectral region near the band gap of silicon, and (3) three dimensional photonic crystals as elements for visionary solar cell concepts including advanced light trapping schemes and luminescent processes.

In the version of this Article originally published, in the ‘Rear-side light trapping’ paragraph of the Methods section, the values of depth and fill factor were incorrectly given as 350 nm and 50%, respectively; instead, the values should have read 250 nm and 60%. This has now been corrected.

Unter einem Ileus wird unabhangig von Ursache und Art jede schwere Storung der Darmpassage bis hin zum vollstandigen Lumenverschluss bzw. zur vollstandigen Darmlahmung verstanden. Darmverschlusse treten oft als akute Ereignisse auf, die unbehandelt sehr schnell in ein lebensbedrohliches Zustandsbild ubergehen konnen. Prinzipiell wird zwischen mechanischem (ca. 70–80% der Falle) und paralytischem (funktionellem) Ileus unterschieden.

We demonstrate diffractive rear side gratings to enhance the near infrared light trapping and thus the quantum efficiency of wafer based crystalline silicon solar cells. Binary crossed gratings with a period of 1 µm, produced via nanoimprint lithography and plasma etching, are electrically decoupled from the solar cell by a thin dielectric passivation layer, creating an electrically flat, but optically rough rear side. We fabricated solar cells with thicknesses of 250, 150 and 100 µm and demonstrate a short circuit current density gain due to the grating of 1.2, 1.6 and 1.8 mA/cm 2 for solar cells with planar front surface. For solar cells with pyramidally textured front surface the grating also leads to a small current density gain in the near infrared of approximately 0.3 mA/cm 2 according to EQE measurements, leading to the best cell's efficiency of 21.1%. By optical simulations we show the potential of the grating structure and identify losses in the fabricated solar cells.

This paper contains a combined experimental and simulation study of the effect of Al and AlInP nanoparticles on the performance of multijunction (MJ) solar cells. In particular, we investigate oblique photon scattering by the nanoparticle arrays as a means of improving thinned subcells or those with low diffusion lengths, either inherently or due to radiation damage. Experimental results show the feasibility of integrating nanoparticle arrays into the antireflection coatings of commercial InGaP/InGaAs/Ge solar cells, and computational results show that nanoparticle arrays can improve the internal quantum efficiency via optical path length enhancement. However, a design that improves the external quantum efficiency of a state-of-the-art cell has not been found, despite the large parameter space studied. We show a clear tradeoff between oblique scattering and transmission loss and present design principles and insights into how improvements can be made.