Accumulated dust on solar cover glass reduces transmittance, leading to decreased energy efficiency of photovoltaic (PV) modules. Hydrophobic coatings on solar cover glass have been shown to provide anti-soiling properties when exposed to a condensing environment (e.g. dew). The addition of hydrophilic features along the top edge of the hydrophobic coated glass enhances condensation rates and can be used to achieve selfcleaning of the surfaces. However, to date, relatively long times have been required to clean the surfaces. In this study, we developed a new design for hydrophilic features that reduce the time required to clean the surface in laboratory tests as measured by laser scanning microscopy, optical photographs and UV-vis spectroscopy. The dagger-shaped features improve self-cleaning performance by a combination of three factors: a silica nanoparticle (NP) hydrophilic coating which enhances condensation rate due to a low water contact angle (WCA) and nano-scale porosity; the stepwise transition from the low WCA silica NP region to the high WCA silanized hydrophobic region via a bare glass transition zone; and the pointed shape of the hydrophobic dagger features which further minimizes the barrier for transport of droplets from the condensing region to the high-mobility, hydrophobic, region of the surface. The hydrophilic silica nanoparticle-coated dagger features not only improve the self-cleaning efficiency of the hydrophobic surfaces but also increase the overall amount of water harvested. Such coating designs provide an effective approach to reducing maintenance costs as well as increasing the overall energy output of PV panels.

Electrochromic devices (ECDs) have a broad range of applications such as smart windows, [1] displays, [2] in the automotive sector (e.g. sunroof, side windows, mirrors, lighting), [3] biosensors, [4] and wearables. [5] ECDs change their transmission when a voltage or a current is applied. Polymeric ECDs are an especially promising technology due to fast switching times, large-scale and efficient wet-chemical roll-to-roll processability and the availability of the full color palette. [6] In the project FLEX-G4.0, funded by the German Federal Ministry for Economic Affairs and Climate Action, a poly-3,4-ethylenedioxythiophene derivative (PEDOT-EthC6) is used to produce flexible large-area ECDs as retrofit smart window solutions for glass facades, with all processing steps from coating to lamination being roll-to-roll methods. [7] The goal is the regulation of the incident solar radiation to improve the visual and thermal comfort inside the buildings. For this application, in particular, the thermal stability of the ECDs is crucial. In this study, the high-temperature cycling stability of the “battery-like” PEDOT-EthC6 and Prussian blue (PB) ECDs on PET-ITO with a UV-cured polymer electrolyte is investigated up to 60 °C. At room temperature, the ECDs show no loss of optical performance over 10,000 switching cycles at ±1.1 V. With the same voltages, a loss of the transmittance modulation of 21% over 10,000 cycles at 60 °C is observed ( Figure 1a ). Analysis of the cycled ECDs by UV-Vis spectroscopy suggested that the PB electrode is overoxidized towards Prussian green, confirmed by temperature-dependent cyclic voltammetry (CV) of the PB electrode. Analog CV measurements of the PEDOT-EthC6 electrode indicate a side reaction of one aggregation state or sub-population. Raman spectroscopy of the PEDOT-EthC6 electrode after CV up to 80 °C shows an altered doping state. Moreover, the CV curves of both electrodes reveal the temperature dependent onset potentials of the side reactions. This information is combined with the CV results of three-electrode ECDs with Lithium as the reference electrode to determine safe switching voltages that avoid side reactions. With voltages of -0.55 V / +1.1 V, 91% of the initial visible light transmittance (τ v ) modulation from 10 % to 65% are retained over 10,000 cycles at 60 °C ( Figure 1b ). The results demonstrate that an adaptation of the switching parameters to temperature can improve the thermal stability of polymeric ECDs, making them more suitable for outdoor applications such as smart windows. [1] R. Tällberg, B. P. Jelle, R. Loonen, T. Gao, M. Hamdy, Sol. Energy Mater Sol. Cells , 2019 , 200 , 109828. [2] A. K. Kamali, D. Lee, R. Futsch, E. Glogic, A. Rougier, G. Sonnemann, ACS Sustainable Chem. Eng. , 2024 , 12 , 1501. [3] C. Y. Jeong, T. Kubota, K. Tajima, RSC Adv. , 2021 , 11 , 28614. [4] M. A. Farahmand Nejad, S. Ranjbar, C. Parolo, E. P. Nguyen, R. Álvarez-Diduk, M. R. Hormozi-Nezhad, A. Merkoçi, Mater. Today , 2021 , 50 , 476. [5] T. G. Yun, M. Park, D.-H. Kim, D. Kim, J. Y. Cheong, J. G. Bae, S. M. Han, I.-D. Kim, ACS nano , 2019 , 13 , 3141. [6] a) H. Wang, M. Barrett, B. Duane, J. Gu, F. Zenhausern, Mater. Sci. Eng. B. , 2018 , 228 , 167; b) W. T. Neo, Q. Ye, S.-J. Chua, J. Xu, J. Mater. Chem. C , 2016 , 4 , 7364. [7] a) L. Brändler, L. Niklaus, M. Schott, G. A. Giffin, P. Löbmann, Adv. Mater. Technol. , 2024 , 2302205; b) S. Macher, M. Schott, M. Dontigny, A. Guerfi, K. Zaghib, U. Posset, P. Löbmann, Adv. Mater. Technol. , 2021 , 6 , 2000836; c) S. Macher, M. Schott, M. Sassi, I. Facchinetti, R. Ruffo, G. Patriarca, L. Beverina, U. Posset, G. A. Giffin, P. Löbmann, Adv. Funct. Mater. , 2020 , 30 , 1906254. Figure 1

The thermal stability of polymeric electrochromic devices (ECDs) on flexible substrates is crucial for most applications. In this study, the high‐temperature cycling stability of the side‐chain modified poly(3,4‐ethylenedioxythiophene) (PEDOT‐EthC6) and Prussian blue (PB) ECDs on indium tin oxide coated polyethylene terephthalate (PET‐ITO) is investigated up to 60 °C. Without a temperature‐dependent voltage control, a loss of optical contrast of 21% over 10 000 cycles at 60 °C and ±1.1 V is observed. Analysis of the cycled ECDs and cyclic voltammetry of the electrodes reveal that side reactions of the EC materials occur during cycling. A local aggregation state of the PEDOT‐EthC6 is degraded. The PB electrode is overoxidized toward Prussian green as confirmed by UV‐vis spectroscopy. Raman spectroscopy shows an altered doping state of the PEDOT‐EthC6 electrode after cyclic voltammetry measurements up to 80 °C. The temperature‐dependent onset potentials of the side reactions are determined. By cyclic voltammetry of ECDs with a Li reference electrode, safe voltage windows are established. With −0.55 V / +1.1 V, 91% of the initial contrast of τ v = 10% ↔ 65% is retained over 10 000 cycles at 60 °C. The results demonstrate that an adaptation of switching parameters for temperature can improve the thermal stability of polymeric ECDs.

Increased particulate matter (PM) concentrations in our ambient air are the cause of various life-threatening diseases and consequently need to be reduced to nonhazardous levels. The natural PM removal capabilities of leaves inspired the development of a low-cost coating technology that exploits natural weather phenomena for its PM catching and removal processes. The herein presented coating is based on microparticle-filled silicone with optimized chemical and physical surface properties. Its surface roughness was tuned using differently sized spray-dried particles, and its surface contact angle was adjusted through silicone tensides, polar ether groups incorporated in the silicon backbone, and the used amount of spray-dried particles. In such a way, optimized silicone coatings showed in laboratory experiments improved catching abilities (>300% relative to glass surfaces), a full retention of adsorbed PM during wind events, and the formation of large PM aggregates. Upon (simulated) rain events, these coatings were regenerated, and the content of harmful PM of various sizes dispersed in water was reduced between ∼73 and 100%. Furthermore, an outdoor test over 100 days showed the functioning of the coating under real-world conditions. These regenerative coatings are readily applicable on diverse surfaces and do not require any further technical infrastructure. Thus, they present an extension of the toolbox for PM reduction technologies.

For the use of polymeric electrochromic devices (ECDs) in architectural or automotive applications, the photostability of the electrochromic (EC) polymer is crucial for long-term durability. In this study, the photostability of the side-chain modified poly(3,4-ethylenedioxythiophene) (PEDOT-EthC6)thin films deposited by roll-to-roll slot-die coating on indium tin oxide coated polyethylene terephtalate (PET-ITO) is investigated and characterized by UV-vis and IR spectroscopy. Residual iron salt on the EC polymer layer, necessary for the in situ polymerization, and the variation of storage times between processing steps have no influence on the degradation rate during light exposure. The photostability of the thin films is 30% better in an inert atmosphere than in ambient conditions. Different long-pass filters are applied to enhance the photostability in the colored and the bleached state. The position of the absorption edge strongly affects the photostability and visual appearance/color of the PEDOT-EthC6 electrodes. The analysis of the CIE L*a*b* color coordinates reveals that a trade-off between stability and a desirable color is necessary. To prevent UV degradation of the EC polymer in flexible ECDs, sputtered nickel oxide is chosen as the counter electrode material. The hybrid ECD shows no sign of degradation and loss of electrochromic performance after 350 h of light exposure. The photostability of roll-to-roll-processed, sidechain-modified poly(3,4-ethylenedioxythiophene) (PEDOT-EthC6) on indium tin oxide coated polyethylene terephtalate (PET-ITO) is improved by excluding ambient atmosphere. In the colored and bleached states, degradation is prevented by 420 and 500 nm long pass filters, respectively. Nickel oxide, as a counter electrode and UV protection, results in ECDs that show no loss of EC performance after 350 h of light exposure. image

Liquid-infused surfaces exhibit remarkable repellency properties toward water, oils, and complex fluids and are widely applied to maintain clean, operational, and high-performing surfaces in various fields, from the biomedical sector to marine infrastructure. Polydopamine (PDA) forms an ideal base layer for the development of such coatings as it adheres to virtually any substrate and can be chemically modified via amino-containing molecules to adjust the surface properties. Here, strategies are explored to increase the mechanical stability of such coatings by i) incorporating imidazole during film formation to increase crosslinking, and ii) formation of a composite consisting of the organic PDA and an inorganic siliceous porous coating by infiltration of a preformed porous silica layer with PDA. Both strategies exhibit improved resistance to tangential shear assessed by a sandpaper abrasion test and to dynamic impact assessed by a sand trickle test. These improved mechanical properties are successfully transferred to liquid-infused surfaces created from such modified PDA base layers. The most durable coatings retain efficient liquid repellency after 25 abrasion cycles, indicating improved resilience in real-world applications.

Soiling of solar cover glass is a major cause for efficiency loss of solar photovoltaic modules. Anti-soiling coatings can be used to reduce the rate of soiling and lower cleaning costs. The efficiency of these coatings has been demonstrated in laboratory and field tests, but the mechanisms and relevant parameters are still not well understood.In this article, we present a study on the influence of surface structure of hydrophilic sol-gel coatings on their anti-soiling performance in terms of both, dust accumulation and subsequent indoor tests for dust removal by wind. The surface structure of the films originates from the addition of colloidal silica particles of different sizes to the sols used for film preparation. In the dust deposition experiments, standardized test dust and dust collected from solar installations were used. Repeated tests were conducted under controlled humidity.In the case of dust deposition, the accumulation of dust particles larger than -10 mu m is strongly reduced, in relation to bare glass, by the anti-soiling effect of all coatings regardless of their surface structure.For the dust removal via wind, coatings that bear a smoother surface structure are cleaned more easily than coatings with a rougher surface structure. Additionally, larger and rounder dust particles are removed more easily from coatings with a rougher surface structure (structure height over -40 nm), while smaller and more irregularly shaped dust particles are removed more easily from coatings with a smoother surface structure.

UV irradiation is used to precharge sputtered tungsten trioxide (WO 3 ) on polyethylene terephthalate enhancing the photochromic response with organic solvents. A comparison between the optical and electrochemical properties of photochemically and electrochemically charged WO 3 results in a correlation of the transmittance to the respective charge density. This allows for a precise control of the charge density in the precharging process monitored by UV–Vis spectroscopy. A proof‐of‐concept flexible electrochromic device combining precharged WO 3 (charge density: 20 mC cm −2 ) and Prussian blue (15 mC cm −2 ) exhibits a superior change in the visible light transmittance (τ v ) from 8% (dark) to 79% (bleached) and a coloration efficiency of 139 cm 2 C −1 at 716 nm.

Although citrates are commonly used to modify nanoparticles, attention is rarely paid to how the modification parameters affect the type of adsorption and, thus, possibly, the properties of the modified particles. The relevance of this and the significant impact it can have is demonstrated in this study by examining the effect of pH upon the modification of superparamagnetic iron oxide nanoparticles (SPIONs) with citrate, using a citrate concentration that yields a high molecular surface density but induces almost no coordination pressure. Relying first on a number of classical surfaces analyzing methods, no clear pH‐dependent differences can be identified. Finally, the consideration of the thermally induced redox behavior gives a decisive clue to unravel the “citric acid mystery” and to put together the, until then, weak hints into an overall picture. This shows that the citrate carboxyl groups are linked to the oxidic surface pH dependently via hydrogen bonds to hydroxide groups or coordinatively to iron ions and, besides, also interact, to a certain extent, with ammonia that is used for pH adjustment. With these findings, it is finally possible to explain the observed differences when the citrate‐modified SPIONs are coated with silica (SiO 2 ) or redispersed after spray‐drying.

Solvent-free inorganic-organic hybrid polymers were prepared for digital light processing (DLP) and ink-jet printing. The resins were characterized in terms of viscosity, surface tension, and refractive index. Optical bulk components were prepared with both printing techniques and compared regarding their surface roughness and optical scattering. The haze of DLP-samples can be avoided by inkjet 3D printing. Moreover, different quantum dots (QD) could be incorporated into resins; DLP resulted in complex 3D assemblies.

Porous MgF2 antireflective λ/4 films were prepared by sol–gel processing and coated with an additional top layer by electron beam evaporation. Scanning Electron Microscopy was applied to characterize the microstructure of the bilayer assembly. It can be shown that the top layer has a protective effect in terms of abrasion resistance and reduced solubility in water. In a second step the thickness of the two film systems has been matched to achieve optimum antireflection properties.

MgF2 coating solutions were prepared by the fluorolytic processing of Mg(OEt)2 and MgCl2. Parts of these sols are solvothermally treated in an autoclave at 160 °C. The two respective precursors were used to prepare porous λ/4 antireflective films by dip-coating on soda-lime and borosilicate glass substrates. UV–Vis spectroscopy and X-Ray diffraction (XRD) were applied to characterize the films as a function of annealing temperature. Samples treated at 500 °C underwent testing of abrasion resistance and water solubility.

Printable organic electrochromic materials are the key component of flexible low power and low weight displays and dynamic shading systems. A vast number of more or less well-performing materials is reported in the literature, but only a very limited number of them have been tested in an industrially-relevant environment so far. Upscaling requires simplicity of synthesis, overall sustainability, low cost and compatibility with simple and high throughput wet-chemical deposition techniques, such as slot-die coating or inkjet printing. In the present paper, an original process is described that enables the controlled oxidative polymerization of a water insoluble, functionalized 3,4-ethylene dioxythiophene (EDOT) derivative. This process leads to the formation of an ink that consists solely of active polymeric material (no dispersing agents) and has suitable rheological properties for use in roll-to-roll slot-die coating or ink-jet printing. The straightforward deposition, followed by a simple thermal treatment, directly yields stable and homogeneous thin films with state-of-the-art electrochromic performance.

This study demonstrates how the method of thermally assisted oxidative precipitation in water can be opened for—the so far neglected—metal organic iron(II) complexes (herein: citrate) in order to obtain, in one step, ferromagnetic magnetite nanoparticles, possessing essential ligand properties. Based on a dedicated analysis of the specific precursor in combination with the consideration of known properties of the ligand, it is possible to identify existing inhibition‐attributes of the iron organyl such that these can be overcome. Moreover, they can be exploited in a targeted manner; thus, simply by changing concentrations, a variety of magnetite nanoparticle morphologies with distinct properties can be obtained. In the case of the herein investigated ferrous citrate, three major inhibition effects are identified. While two of them efficiently prevent the formation of magnetite and need to be addressed to be overcome, the third can be exploited to selectively synthesize, for example, relatively stable carboxyl group‐bearing nuclei clusters, exhibiting the properties of magnetically responsive photonic crystals, or relatively large mesocrystals, whose intraparticular magnetic interactions are apparently disturbed.

Oxidative precipitation is a facile synthesis method to obtain ferromagnetic iron oxide nanoparticles from ferrous salts—with unexplored potential. The concentration of base and oxidant alone strongly affects the particle's structure and thus their magnetic properties despite the same material, magnetite (Fe 3 O 4 ), is obtained when precipitated with potassium hydroxide (KOH) from ferrous sulfate (FeSO 4 ) and treated with potassium nitrate (KNO 3 ) at appropriate temperature. Depending on the potassium hydroxide and potassium nitrate concentrations, it is possible to obtain a series of different types of either single crystals or mesocrystals. The time‐dependent mesocrystal evolution can be revealed via electron microscopy and provides insights into the process of oriented attachment, yielding faceted particles, showing a facet‐dependent reactivity. It is found that it is the nitrate and hydroxide concentration that influences the ligand exchange process and thus the crystallization pathways. The presence of sulfate ions contributes to the mesocrystal evolution as well, as sulfate apparently hinders further crystal fusion, as revealed via infrared spectroscopy. Finally, it is found that nitrite, as one possible and ecologically highly relevant reduction product occurring in nature in context with iron, only evolves if the reaction is quantitative.

Sol–gel formulations were applied to replace silicone as matrix material for phosphors in pc-LEDs. The content of organic groups was minimized in order to reduce yellowing during the operation of the elements. It was possible to evenly embed YAG:Ce particles in sol–gel binders. Further processing on LED chips resulted in operational light sources; and their performance was compared to standard silicone-based elements. Additional deposition of ALD laminates seals possible defects within the sol–gel matrix as additional protection of the phosphors and the underlying LEDs.

Large‐area electrochromic devices (ECDs) based on a cathodically‐coloring, side chain‐modified poly(3,4‐ethylene dioxythiophene) (PEDOT) derivative and anodically‐coloring Prussian blue (PB) are assembled by a customized sheet‐to‐sheet (S2S) lamination process. The ECDs with two complementary switching “half‐cells”, based on flexible PET‐ITO substrates, offer enhanced optical properties in terms of visible light transmission change (4–53%), contrast ratio (CR = 93.4) and color neutrality (L* = 77.9, a* = −5.9, b* = −0.6) in the bleached state. The cycling stability is monitored for up to 10 000 switching cycles (97% charge retention). The reported optical, electrochemical, and in operando (in situ) spectroelectrochemical data are obtained from small laboratory‐scale ECDs (active area: 5 × 5 cm 2 ). These results, the homogeneity of the large‐area devices and the scalability of the S2S lamination process are confirmed by measurements on the large ECDs with an active area of 45 × 65 cm 2 . This large‐area electrochromic film technology with high optical contrast and enhanced cycling stability offers an excellent perspective for further development and scale‐up towards pilot production and the commercialization of flexible ECDs upon their unique materials and processing characteristics.

The availability of stretchable conductive materials is a key requirement for the development of soft and wearable electronics. Although there are many promising materials, the characterization of these materials under realistic conditions is complex and a standardized and reliable procedure has not been etablished yet. We therefore introduce a comprehensive protocol for the practice-oriented dynamic electro-mechanical analysis of elastomer-particle composites. In addition to strain dependence (0-100% strain) and fatigue strength (10,000 cycles), this protocol aims in particular to clarify the influence of strain rate (0-100% s(-1)) on conductivity. Samples with the commonly used filler representatives carbon black and silver flakes with 20 vol% each were prepared and investigated. Silicone elastomers of different stiffness were used as matrix in order to determine its influence. We found that while the conductivity of the carbon black composites of about 1 x 10(2) S m(-1) proved to be fatigue resistant and largely independent of the strain rate, the silver flake composites lost their initially higher conductivity of 1 x 10(4) S m(-1) at high strain rates and increasing numbers of cycles. In addition, the use of a softer silicone matrix improved the performance of both particle composites, which was also demonstrated on an exemplary wearable electronic device.

The cycling stability of flexible electrochromic devices (ECDs) under humid atmospheres is limited by irreversible indium tin oxide (ITO) reduction. A strategy to limit this degradation was developed and tested for model ECDs based on a sidechain-modified poly(3,4-ethylene dioxythiophene) (PEDOT) derivative and Prussian blue (PB). This work reveals that the cycling stability is reduced by dissolution of the ITO thin films and formation of metallic indium particles on the surface of the ITO layers. The ITO degradation strongly depends on the applied electrode potentials in combination with moisture ingress into the ECDs. To avoid ITO reduction in ECDs, efforts were made to adjust the electrode potentials. ECDs equipped with an auxiliary reference electrode were set up to gather knowledge on the actual electrode potentials. By adjusting the electrode charge density ratio, it was possible to narrow the overall cell voltage window to an extent in which irreversible ITO reduction no longer occurs. Detailed investigation of ECDs with the optimized cell configuration (charge density ratio) showed that the overall device performance with regard to visible light transmittance change and response time is not impaired and that the cycling stability under humid atmosphere (90% rH) is dramatically improved. Thus, the proposed strategy offers an excellent perspective for the commercialization of flexible ECDs upon their enhanced durability.

Conjugated electrochromic (EC) polymers for flexible EC devices (ECDs) generally lack a fully colorless bleached state. A strategy to overcome this drawback is the implementation of a new sidechain‐modified poly(3,4‐ethylene dioxythiophene) derivative that can be deposited in thin‐film form in a customized high‐throughput and large‐area roll‐to‐roll polymerization process. The sidechain modification provides enhanced EC properties in terms of visible light transmittance change, Δτ v = 59% (Δ L* = 54.1), contrast ratio (CR = 15.8), coloration efficiency (η = 530 cm² C −1 ), and color neutrality ( L* = 83.8, a* = −4.3, b* = −4.1) in the bleached state. The intense blue‐colored polymer thin films exhibit high cycle stability (10 000 cycles) and fast response times. The design, synthesis, and polymerization of the modified 3,4‐ethylene dioxythiophene derivative are discussed along with a detailed optical, electrochemical, and spectroelectrochemical characterization of the resulting EC thin films. Finally, a flexible see‐through ECD with a visible light transmittance change of Δτ v = 47% (Δ L* = 51.9) and a neutral‐colored bleached state is developed.