Micron‐scale textures at the front surface of solar modules have been reported to improve the current generation by both enhancing light in‐coupling as well as by reducing light out‐coupling via ...back‐reflection, similar to the retroreflective effect. Whereas the general working principle and advantages of these textures have been described previously, here, the interplay of the reflection properties of different substrates with the enhancement effects is analyzed for textures of conical geometry. The study takes into consideration the incident light of arbitrary angle of incidence as well as the overall energy yield. Supported by optical simulations, periodic micro‐cone textures were optimized and prototyped based on direct laser writing and a scalable replication process. Micron‐scale textures with cones of various aspect ratios were examined on mono‐crystalline silicon (c‐Si) solar cells; an optimum aspect ratio of 0.73 was identified. This moderate aspect ratio is suitable for large‐scale replication, while showing near‐zero surface reflection and excellent light trapping. An increase in energy yield of up to 8% was calculated for the case of micro‐cone textures at the front surface of commercial alkaline‐etched c‐Si solar cells. Moreover, the excellent optical properties of the micro‐cone textures were highlighted by improving the power conversion efficiency (PCE) of a Cu(In,Ga)Se2 (CIGS) thin‐film solar cells from 20.2% to 20.9%. A comparable PCE improvement has been achieved by conventional MgF2 antireflection coatings, but the angular stability and in turn the energy yield of the micro‐cone textures is much higher.
Micron‐scale textures applied to the front surface of solar modules enhance the transmission to the underlying solar cells and trap light reflected from the solar cells. A systematic experimental study of conical micro‐textures is performed, focusing on the aspect ratio. The interaction between the texture and solar cell is investigated in detail, and the angle‐stable performance enhancement on different photovoltaic devices is demonstrated.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Solar‐pumped lasers (SPLs) typically couple sunlight into the laser cavity using focusing optics and solar tracking. Luminescent solar concentrators (LSC) are an alternative, fully planar, scalable ...pump source that can concentrate diffuse light. For liquid LSC‐based SPLs, reflective cavities have been used to trap light and pump a Nd3+‐doped silica fiber. Here, three solid‐state LSC‐based SPL designs, in addition to the reflective cavity making use of total internal reflection, are analyzed by ray‐tracing simulations. Results are compared to a liquid LSC reference, also used for validating simulations. Substituting the liquid‐state LSC for a solid‐state LSC (with the fiber placed inside) allows a 7‐fold enhancement of the gain coefficient, corresponding to a 30‐fold enhancement of the laser output power. An additional 4‐fold increase of the output power is possible with a fiber of kilometers length. These results show a roadmap for realizing SPLs with output powers on the order of 2.8 W m−2 under terrestrial sunlight, while keeping an identical reflective cavity used for the liquid LSC design. In addition, room‐temperature operation should be possible with certain solid LSC designs, and the necessity for a reflective cavity comprised of costly dielectric mirrors may be relieved.
Ray‐tracing simulations demonstrate that the performance of solar‐pumped lasers (SPLs), based on solid‐state luminescent concentrators, should significantly exceed the best experimental results achieved for fiber‐based SPLs pumped by liquid‐state luminescent concentrators. Embedding a fiber of optimized length into a specially designed solid‐state luminescent concentrator is a promising route for producing scalable SPLs.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In article number 2100479, Stephan Dottermusch, Ian A. Howard and co‐workers use ray‐tracing simulations to demonstrate how the performance of lightweight, scalable, solar‐pumped lasers can be ...boosted by luminescent concentrators. Embedding the solar‐pumped laser's fiber in an appropriately designed solid‐state luminescent concentrator leads to significant enhancement of the output power compared with current designs also based on radiative energy transfer.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Ultrathin crystalline silicon (c-Si) solar cells represent an important technology development direction for reducing material usage and thus lowering the cost of solar electricity. Here, we ...demonstrate a prototype device with high efficiency assisted by a micro-/nano-structured polycarbonate thin nanofur film inspired by water ferns. The ultrathin c-Si solar cells consist of a 17 μm-thick c-Si absorber and exhibit an efficiency of up to 17.3% and short-circuit current density (Jsc) of 35.8 mA cm−2. With the assistance of the thin nanofur, the efficiency is increased to 18.1% due to an increase in Jsc to 37.4 mA cm−2. The photocurrent enhancement is attributed to, firstly, a more favorable refractive index transition due to the polymer addition and, secondly, the high forward scattering of the structured film, which increases the optical pathlength within the ultrathin absorber layer of the devices. To our knowledge, the present prototype device demonstrates the highest Jsc and efficiency in the area of ultrathin c-Si solar cells with an absorber layer of less than 20 µm.
•17 μm-thick ultrathin crystalline Si solar cell fabricated with 18.1% efficiency.•Photocurrent enhancement of 1.6 mA cm−2 realised via bioinspired polymeric “nanofur”.•An absolute efficiency improvement of Δη = 0.8% is achieved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Advanced optical concepts, making use of tailored microstructured front cover glasses, promise to reduce the losses encountered with encapsulated solar modules. However, implementing optical concepts ...into the conventional architecture of encapsulated solar modules and simultaneously maintaining high durability represent a severe technological challenge. The liquid glass technique offers a route to meet this challenge by enabling the implementation of these optical concepts directly into the durable front cover glass of solar modules. In this work, we demonstrate for the first time two showcases of texturing fused silica front cover glass, using the facile liquid glass technique: (I) multifunctional microcone textures that reduce front-side reflection losses by ∼80% compared to a planar reference, which correlates to an increase in short-circuit current density of encapsulated planar monocrystalline silicon heterojunction solar cells by 2.9 mA cm–2, and exhibit strong hydrophilic behavior facilitating self-cleaning and (II) embedded freeform surface cloaks that redirect incident light away from the metallic contact grids of the solar cell and demonstrate a cloaking efficiency of ∼88%.
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IJS, KILJ, NUK, PNG, UL, UM
Air‐stable inorganic cesium lead iodide (CsPbI
3
) perovskite thin films with a bandgap of 1.7 eV are a promising candidate for tandem cell solar cells, comprising a perovskite top cell with a ...crystalline silicon bottom cell. The device design and simulations are important to develop high‐efficiency photovoltaic devices. However, knowledge of complex optical constants of the CsPbI
3
thin films is mandatory to complement such tasks. Herein, air‐stable inorganic CsPbI
3
perovskite thin films are prepared using one‐step synthesis through a spin‐coating method. Variable angle spectroscopic ellipsometry (VASE) is then conducted at five angles (43.9°, 48.9°, 53.9°, 58.9°, and 63.9°) to obtain ellipsometric data (Ψ and Δ). The thickness nonuniformity model of the perovskite thin film combined with an effective medium approximation for describing rough surface is adopted to achieve excellent fitting. The complex optical constants of the CsPbI
3
thin film are experimentally obtained in the wavelength range of 300–1200 nm. The present results open the door for design and simulations on high‐efficiency CsPbI
3
/c‐Si tandem solar cells.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A phosphor‐particle‐loaded microlens array on a polymer substrate offers an attractive unclonable anticounterfeiting label design. A random pattern of bright emission points is created due to the ...random coincidences of light focused by a microlens with an underlying phosphor microparticle. The change of the bright point patter with the angle of the incident light (owing to a shift in the locations of the focal points) makes the labels unclonable. This work examines the authentication of such labels using a single smartphone. The smartphone flashlight provides illumination whereas the camera is used for detection (optical filters prevent capture of scattered source light). A 196‐bit binary string is created from the captured images to identify which lenses in the 14 × 14 array create bright emission points for a given position of the smartphone. The classification of test and reference images as matching or not is achieved with >99% confidence, as is a 1 cm tolerance for the positioning accuracy of the smartphone. Moreover, authentication is possible for different distances between flash and camera provided this is less than 3 cm. In summary, the present work quantifies the good potential of the microlens array microphosphor unclonable label concept for authentication using a smartphone.
An unclonable label designed to be authenticated using a smartphone is presented. The label is made from a microlens array on top of a phosphor‐doped layer. A pattern of emission points is observed with the camera when the label is excited by the flashlight. This pattern change as the phone is moved making the labels highly resistant to cloning.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Advanced optical concepts, making use of tailored micro-structured front cover glasses, promise to reduce the losses encountered with encapsulated solar modules. However, implementing optical ...concepts into the conventional architecture of encapsulated solar modules and simultaneously maintaining high durability represents a severe technological challenge. The liquid glass technique offers a route to meet this challenge by enabling the implementation of these optical concepts directly into the durable front cover glass of solar modules. In this work, we demonstrate for the first time two showcases of texturing fused silica front cover glass, using the facile liquid glass technique: (I) multi-functional micro-cone textures that reduce front-side reflection losses by ~80 % compared to a planar reference and exhibit strong hydrophilic behavior facilitating self-cleaning; and (II) embedded freeform surface cloaks that redirect incident light away from the metallic contact grids of the solar cell and demonstrate a cloaking efficiency of ~88 %.
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IJS, KILJ, NUK, PNG, UL, UM
Micron-scale randomness during manufacturing can ensure anti-counterfeiting labels are unclonable. However, this security typically comes at the expense of complex hardware being needed for ...authentication (e.g., microscopy systems). We demonstrate unclonable labels that can be authenticated using a standard light-emitting diode and smartphone camera. The labels consist of a microlens array laminated to a polymer film that is doped with luminescent microparticles. The micron-scale random overlap of focal volumes and microparticles leads to a pattern of bright points of visible light emission that can be easily imaged by a smartphone camera. 10 000 comparisons of images demonstrate that the labels can be robustly authenticated, and that the probability of a false authentication is on the order of \(10^{-15}\). The ability for microlens arrays to simplify the hardware needed for authentication of unclonable labels is generalizable, and attractive for the implementation of unclonable labels in anti-counterfeiting systems.
Intraocular medulloepithelioma (IO-MEPL) is a rare embryonal ocular neoplasm, prevalently occurring in children. IO-MEPLs share histomorphological features with CNS embryonal tumors with multilayered ...rosettes (ETMRs), referred to as intracranial medulloepitheliomas. While Sonic hedgehog (SHH) and WNT signaling pathways are crucial for ETMR pathogenesis, the impact of these pathways on human IO-MEPL development is unclear. Gene expression analyses of human embryonal tumor samples revealed similar gene expression patterns and significant overrepresentation of SHH and WNT target genes in both IO-MEPL and ETMR. In order to unravel the function of Shh and Wnt signaling for IO-MEPL pathogenesis in vivo, both pathways were activated in retinal precursor cells in a time point specific manner. Shh and Wnt co-activation in early Sox2- or Rax-expressing precursor cells resulted in infiltrative ocular lesions that displayed extraretinal expansion. Histomorphological, immunohistochemical, and molecular features showed a strong concordance with human IO-MEPL. We demonstrate a relevant role of WNT and SHH signaling in IO-MEPL and report the first mouse model to generate tumor-like lesions with features of IO-MEPL. The presented data may be fundamental for comprehending IO-MEPL initiation and developing targeted therapeutic approaches.
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