Radiation-Induced Graft Immobilization (RIGI): Covalent Binding of Non-Vinyl Compounds on Polymer Membranes

Radiation-induced graft immobilization (RIGI) is a novel method for the covalent binding of substances on polymeric materials without the use of additional chemicals. In contrast to the well-known radiation-induced graft polymerization (RIGP), RIGI can use non-vinyl compounds such as small and large functional molecules, hydrophilic polymers, or even enzymes. In a one-step electron-beam-based process, immobilization can be performed in a clean, fast, and continuous operation mode, as required for industrial applications. This study proposes a reaction mechanism using polyvinylidene fluoride (PVDF) and two small model molecules, glycine and taurine, in aqueous solution. Covalent coupling of single molecules is achieved by radical recombination and alkene addition reactions, with water radiolysis playing a crucial role in the formation of reactive solute species. Hydroxyl radicals contribute mainly to the immobilization, while solvated electrons and hydrogen radicals play a minor role. Release of fluoride is mainly induced by direct ionization of the polymer and supported by water. Hydrophobic chains attached to cations appear to enhance the covalent attachment of solutes to the polymer surface. Computational work is complemented by experimental studies, including X-ray photoelectron spectroscopy (XPS) and fluoride high-performance ion chromatography (HPIC)

Subwavelength Custom Wavefront Shaping by a Nonlinear Electro-optic Spatial Light Modulator

Holographic displays offer a method to completely reconstruct any desired wavefront and can thus lead to breakthrough innovation in beamforming, sensing, and information encryption. However, full control over a wavefront in the visible requires features of 100 nm or less. Here, we apply these stringent requirements in an all-encompassing device structure including light source, modulator, and driver electronics. To this end, we propose a continuous electro-optically modulated barium titanate slab waveguide employing a metamaterial cladding layer enabling electrodes to be in contact with the optically active layer. This prevents both the undesired scattering and the absorption that metallic electrodes would introduce. We elaborate the driving requirements of the proposed waveguide display including the optimal use of a nonlinear barium titanate crystal and electrical and optical simulations that show complete control over a waveguided mode, resulting in desired holographic imaging in far-field simulations

Perovskite Light Emitting Diode Characteristics: The Effects of Electroluminescence Transient and Hysteresis

The reproducibility of results is one of the corner stones of scientific research. However, in emerging technologies, the reported results often tend to be sensitive to the chosen measurement protocol. This can stem from measurement artifacts or from unknown complex underlying phenomena. Metal halide perovskites have emerged as an exciting material system for optoelectronic devices. The anomalous hysteresis in the current density-voltage (J-V) characteristics of perovskite solar cells has triggered wide discussions on how to report their power conversion efficiency (PCE) to achieve consistency between different research groups. However, less attention is so far given to the anomalous effects that can affect the reporting of the characteristics of perovskite light emitting diodes (PeLEDs). Here, we show that even for PeLEDs with little J-V hysteresis, the transient response and hysteresis of electroluminescence (EL), likely caused by ion migration, heat accumulation and device degradation under electrical excitation, can lead to significantly different device characteristics depending on the measurement procedures for the same device. Therefore, we propose a method based on pulsed excitation that allows better reproducibility and interpretation of the measured device characteristics. Furthermore, we also provide suggestions on reporting PeLED characteristics, as input for further discussions in the scientific community.status: publishe

Non-linear electro-optic modelling of a Barium Titanate grating coupler

We provide insight into the driving mechanisms and requirements to create an electro-optic spatial light modulator based on a Barium Titanate waveguide and an optically transparent electrode cladding layer. We have developed a generic framework of electric field simulations and non-linear optics to create any desired modulation in an area of interest, applicable for liquid crystals, Pockels and Kerr cells. Targeting our device structure, we have evaluated several design parameters of the arbitrarily reprogrammable SLM, capable of optical beamforming and high-quality holograms.status: publishe

Perovskite modules with 99% geometrical fill factor using point contact interconnections design

Thin‐film photovoltaic technology, based on hybrid metal halide perovskites, has achieved 25.2% and 16.1% certified power conversion efficiencies for solar cell and solar module devices, respectively. Still, the gap between power conversion efficiency of small area solar cells and large area solar modules is greater than for any other photovoltaic technology. Analysis of loss mechanisms in n‐i‐p solution processed devices defined layer inhomogeneity loss and inactive area loss as the two most prominent loss mechanisms in upscaling. In this study, we focus on minimizing inactive area loss. We analyze the point contact interconnections design and demonstrate it on perovskite thin‐film solar modules to achieve a geometrical fill factor of up to 99%. Numerical and analytical simulations are utilized to optimize interconnections and solar module design and balance inactive area loss, series resistance loss, and contact resistance loss

Perovskite modules with 99% geometrical fill factor using point contact interconnections design

status: publishe

Radiation-Induced Graft Immobilization (RIGI): Covalent Binding of Non-Vinyl Compounds on Polymer Membranes

Radiation-induced graft immobilization (RIGI) is a novel method for the covalent binding of substances on polymeric materials without the use of additional chemicals. In contrast to the well-known radiation-induced graft polymerization (RIGP), RIGI can use non-vinyl compounds such as small and large functional molecules, hydrophilic polymers, or even enzymes. In a one-step electron-beam-based process, immobilization can be performed in a clean, fast, and continuous operation mode, as required for industrial applications. This study proposes a reaction mechanism using polyvinylidene fluoride (PVDF) and two small model molecules, glycine and taurine, in aqueous solution. Covalent coupling of single molecules is achieved by radical recombination and alkene addition reactions, with water radiolysis playing a crucial role in the formation of reactive solute species. Hydroxyl radicals contribute mainly to the immobilization, while solvated electrons and hydrogen radicals play a minor role. Release of fluoride is mainly induced by direct ionization of the polymer and supported by water. Hydrophobic chains attached to cations appear to enhance the covalent attachment of solutes to the polymer surface. Computational work is complemented by experimental studies, including X-ray photoelectron spectroscopy (XPS) and fluoride high-performance ion chromatography (HPIC)

Reduced Efficiency Roll-Off and Improved Stability of Mixed 2D/3D Perovskite Light Emitting Diodes by Balancing Charge Injection

status: publishe

Touchscreen tags based on thin-film electronics for the Internet of Everything

Capacitive touchscreens are increasingly widespread, featuring in mobile phones and tablets, as well as everyday objects such as cars and home appliances. As a result, the interfaces are uniquely placed to provide a means of communication in the era of the Internet of Everything. Here we show that commercial touchscreens can be used as reader interfaces for capacitive coupled data transfer. The transfer of data to the touchscreen is achieved using a 12-bit thin-film capacitive radio frequency identification tag powered by a thin-film battery or a thin-film photovoltaic cell that converts light from the screen. The thin-film integrated circuit has a 0.8 cm2 on-chip monolithic antenna, employs 439 transistors, and dissipates only 31 nW of power at a supply voltage of 600 mV. The chip has an asynchronous data rate of up to 36 bps, which is limited by the touchscreen readout electronics.status: publishe