Loss Of Device Performance Research Articles

Ultra-Broadband, Compact Arbitrary-Ratio Multimode Power Splitter Based on Tilted Subwavelength Gratings

Mode division multiplexing (MDM) technology is an effective solution for high-capacity optical interconnection, and multimode power splitters, as essential components in MDM systems, have attracted widespread attention. However, supporting a wide range of modes and arbitrary power splitting ratios with large bandwidth in power splitters remains a significant challenge. In this paper, we designed a power splitter based on a subwavelength grating (SWG) structure with tilted placement on a silicon-on-insulator (SOI) substrate. We achieve arbitrary TE0–TE9 mode-insensitive power distribution by altering the filling coefficient of the SWG. Thanks to our specific selection of cladding materials and compensatory design for the optical wave transmission and reflection shifts induced by SWG, our device demonstrates low additional loss (EL < 1.1 dB) and inter-mode crosstalk (−18.8 < CT < −60 dB) for optical modes ranging from TE0 to TE9, covering a wavelength range from 1200 nm to 1700 nm. Furthermore, our proposed device can be easily extended to higher-order modes with little loss of device performance, offering significant potential in MDM platforms.

Sustainable solvent selection for the manufacture of methylammonium lead triiodide (MAPbI3) perovskite solar cells

An approach for screening solvent systems for PSCs to substitute REACH restricted DMF with no loss in device performance.

Thermally Stable, Efficient, Vapor Deposited Inorganic Perovskite Solar Cells

We report on thermally stable inorganic mixed halide perovskite solar cells deposited using a vapor deposition technique with no loss in device performance at 200 °C for 72 h. X-ray diffraction ana...

Physical insights into the operation of a 1-nm gate length transistor based on MoS2 with metallic carbon nanotube gate

Low-dimensional materials such as layered semiconductors or carbon nanotubes (CNTs) have been attracting increasing attention in the last few decades due to their inherent scaling properties, which become fundamental to sustain the scaling in electronic devices. Inspired by recent experimental results [Desai et al., Science 354, 99 (2016)], in this work we examined the ultimate performance of MoS2-channel Field Effect Transistors with a gate length of 1 nm by means of quantum transport simulations based on the Poisson equation and non-equilibrium Green's function formalism. We considered uniformly scaled devices, with channel lengths ranging from 5 to 20 nm controlled by a cylindrical gate with a diameter of 1 nm, as would be required in realistic integrated circuits. Moreover, we also evaluated the effect of the finite density of states of a carbon nanotube gate on the loss of device performance. We noticed that the sub-threshold swing for all short-channel structures was greater than the ideal 60 mV per decade limit of thermionic devices, and we attributed this to the presence of tunneling currents and gate-drain interactions. We tailored the transistor architecture in order to improve the gate control. We concluded that the limited CNT-channel capacitive coupling poses severe limitations on the operation and thus exploitation of the device.

Stable Water Oxidation in Acid Using Manganese-Modified TiO2 Protective Coatings

Accomplishing acid-stable water oxidation is a critical matter for achieving both long-lasting water-splitting devices and other fuel-forming electro- and photocatalytic processes. Because water oxidation releases protons into the local electrolytic environment, it becomes increasingly acidic during device operation, which leads to corrosion of the photoactive component and hence loss in device performance and lifetime. In this work, we show that thin films of manganese-modified titania, (Ti,Mn)O x, topped with an iridium catalyst, can be used in a coating stabilization scheme for acid-stable water oxidation. We achieved a device lifetime of more than 100 h in pH = 0 acid. We successfully grew (Ti,Mn)O x coatings with uniform elemental distributions over a wide range of manganese compositions using atomic layer deposition (ALD), and using X-ray photoelectron spectroscopy, we show that (Ti,Mn)O x films grown in this manner give rise to closer-to-valence-band Fermi levels, which can be further tuned with annealing. In contrast to the normally n-type or intrinsic TiO2 coatings, annealed (Ti,Mn)O x films can make direct charge transfer to a Fe(CN)63-/4- redox couple dissolved in aqueous electrolytes. Using the Fe(CN)63-/4- redox, we further demonstrated anodic charge transfer through the (Ti,Mn)O x films to high work function metals, such as iridium and gold, which is not previously possible with ALD-grown TiO2. We correlated changes in the crystallinity (amorphous to rutile TiO2) and oxidation state (2+ to 3+) of the annealed (Ti,Mn)O x films to their hole conductivity and electrochemical stability in acid. Finally, by combining (Ti,Mn)O x coatings with iridium, an acid-stable water-oxidation anode, using acid-sensitive conductive fluorine-doped tin oxides, was achieved.

Optimization, characterization and upscaling of aqueous solar nanoparticle inks for organic photovoltaics using low-cost donor:acceptor blend

Abstract We present the optimization and upscaling of water-based nanoparticle inks based on a novel donor-acceptor pair consisting of poly(3-hexylthiophene) (P3HT) and a newly developed indene-C 60 multiadducts (ICxA) that is comprised of indene-C 60 monoadduct (ICMA), indene-C 60 bisadduct (ICBA), and indene-C 60 trisadduct (ICTA). This material system has been used as a case study to explore the transition from OPV materials optimised for small-scale spin-coating to those optimised for large-scale printing. In particular, we have explored the effects of transitioning from a small-scale BHJ ink formulated from a high-cost acceptor to a large-scale NP ink formulated from a low-cost fullerene mixture. We show that it is possible to use a low-cost acceptor and to formulate the inks at scale with no loss in device performance.

Integrating Nanostructured Artificial Receptors with Whispering Gallery Mode Optical Microresonators via Inorganic Molecular Imprinting Techniques.

The creation of label-free biosensors capable of accurately detecting trace contaminants, particularly small organic molecules, is of significant interest for applications in environmental monitoring. This is achieved by pairing a high-sensitivity signal transducer with a biorecognition element that imparts selectivity towards the compound of interest. However, many environmental pollutants do not have corresponding biorecognition elements. Fortunately, biomimetic chemistries, such as molecular imprinting, allow for the design of artificial receptors with very high selectivity for the target. Here, we perform a proof-of-concept study to show how artificial receptors may be created from inorganic silanes using the molecular imprinting technique and paired with high-sensitivity transducers without loss of device performance. Silica microsphere Whispering Gallery Mode optical microresonators are coated with a silica thin film templated by a small fluorescent dye, fluorescein isothiocyanate, which serves as our model target. Oxygen plasma degradation and solvent extraction of the template are compared. Extracted optical devices are interacted with the template molecule to confirm successful sorption of the template. Surface characterization is accomplished via fluorescence and optical microscopy, ellipsometry, optical profilometry, and contact angle measurements. The quality factors of the devices are measured to evaluate the impact of the coating on device sensitivity. The resulting devices show uniform surface coating with no microstructural damage with Q factors above 106. This is the first report demonstrating the integration of these devices with molecular imprinting techniques, and could lead to new routes to biosensor creation for environmental monitoring.

Parameters responsible for the degradation of CH3NH3PbI3-based solar cells on polymer substrates

Despite the rapid progress made in the field of perovskite solar cells, their instability remains a major obstacle for commercialization. Here, focus is placed on the stability of CH3NH3PbI3 solar cells on polymer substrates and the understanding of the factors influencing device degradation. A range of storage conditions is used, parameters such as light or temperature are isolated, and their impacts on the perovskite film examined. The severe loss in device performance is not predominantly correlated to the perovskite film deterioration, which implies that the device failure originates elsewhere. This study demonstrates that the hole transport material plays a significant role in the device degradation, and thus its optimization or removal can potentially lead to enhanced device lifetime.

Water Ingress in Encapsulated Inverted Organic Solar Cells: Correlating Infrared Imaging and Photovoltaic Performance

Understanding the degradation and failure mechanisms of organic photovoltaic devices is a key requirement for this technology to mature toward a reliable product. Here, an investigation on accelerated temperature and moisture long‐term stability testing (>20 000 h) of inverted and glass‐encapsulated poly(3‐hexylthiophene)/phenyl‐C61‐butyric acid methyl ester solar cells is presented. The degradation kinetics is analyzed using the Arrhenius model and the resulting activation energy for the diffusion of water is measured to be ≈43 kJ mol−1. Through comparison of electroluminescence imaging, lock‐in thermography, and photoluminescence mapping, the device performance is correlated with the loss of effective cell area and it is shown that the reaction of water at the hole extraction/active layer interface is likely to be the dominant cause for long‐term device failure. The diffusion of water through the packaged solar cell is described using classical diffusion theory. Based on an analytical solution of a simple diffusion model, the diffusion coefficient is estimated to be 4 × 10−12 m2 s−1. A shelf life of 100 000 h is anticipated at 65 °C/85% RH using a 9.3 cm wide protective adhesive rim. The findings of this study may inform strategies for predicting lifetimes of organic solar cells and modules based on local in situ tracking of moisture‐induced device performance loss using IR imaging.

Interlayer adhesion in roll-to-roll processed flexible inverted polymer solar cells

The interlayer adhesion of roll-to-roll processed flexible inverted P3HT:PCBM bulk heterojunction (BHJ) polymer solar cells is reported. Poor adhesion between adjacent layers may result in loss of device performance from delamination driven by the thermomechanical stresses in the device. We demonstrate how a thin-film adhesion technique can be applied to flexible organic solar cells to obtain quantitative adhesion values. For the P3HT:PCBM-based BHJ polymer solar cells, the interface of the BHJ with the conductive polymer layer PEDOT:PSS was found to be the weakest. The adhesion fracture energy varied from 1.6 J/m 2 to 0.1 J/m 2 depending on the composition of the P3HT:PCBM layer. Post-deposition annealing time and temperature were shown to increase the adhesion at this interface. Additionally the PEDOT:PSS cells are compared with V 2O 5 cells whereby adhesive failure marked by high fracture energies was observed.

Ultra-Shallow Junction Formation Using Rapid Thermal Processing

One of the main materials challenges of the 130 nm silicon technology node was the need to find a processing solution to the anomalous diffusion behavior of ion-implanted dopants known from three decades of research. Reduction of implantation energy no longer proved sufficient when trying to reduce source/drain extension junction depth, increase abruptness, and limit sheet resistance. Spike-annealing, a new process in which ion implanted silicon could be heated rapidly to temperatures required for dopant activation and then cooled down without dwelling at temperature, adequately addressed the scaling requirements of this node. The resulting junctions achieved high dopant concentration values very close to the surface while limiting junction depth. However, this increased the propensity for dopant migration to overlying layers associated with the source/drain spacer. Loss of device performance due to this and other phenomena became a strong motivating factor for further materials research in order to sustain progress through the 130 nm and 90 nm nodes. Complex interactions between various layers have been understood and the resulting developments in spacer materials have enabled high performance devices. The requirements of the 65 and 45 nm nodes stretch spike-annealing to its limit and newer ultra-high temperature anneals must be considered.

ITO-free wrap through organic solar cells—A module concept for cost-efficient reel-to-reel production

Organic solar cells have the potential to make cheap photovoltaic devices feasible. In order to achieve this, material and production costs have to be minimised by using device architectures, which are suited to tap the full potential of reel-to-reel production. The inversion of the layer sequence in organic bulk-heterojunction solar cells is motivated by the possibility to omit the commonly used expensive indium tin oxide electrode utilising the so-called wrap through concept. In this concept, the hole contact is formed by a highly conductive formulation of poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate), which is led through via holes in the solar cell to the backside of the substrate in a regular pattern, where it is contacted with a metal layer with low sheet resistance. In this way, a scalable parallel connexion is realised. If higher voltage is desired, one can also connect several such cell segments in series monolithically. We will show that the inversion of the layer sequence is possible without loss of device performance. Using the results of small area inverted devices, we calculate the optimal dimensions of the wrap through solar cell module. First devices with active areas of 2–4 cm 2 with parallel and serial wrap through connexion will be shown as proof of concept.

Ultra-Shallow Junction Formation Technology from the 130 to the 45 nm node

ABSTRACTOne of the main materials challenges of the 130 nm silicon technology node was the need to find a processing solution to the anomalous diffusion behavior of ion-implanted dopants known from three decades of research. Reduction of implantation energy no longer proved sufficient when trying to reduce source/drain extension junction depth, increase abruptness, and limit sheet resistance. Spike-annealing, a new process in which ion implanted silicon could be heated rapidly to temperatures required for dopant activation and then cooled down without dwelling at temperature, adequately addressed the scaling requirements of this node. The resulting junctions achieved high dopant concentration values very close to the surface while limiting junction depth. However, this increased the propensity for dopant migration to overlying layers associated with the source/drain spacer. Loss of device performance due to this and other phenomena became a strong motivating factor for further materials research in order to sustain progress through the 130 nm and 90 nm nodes. Complex interactions between various layers have been understood and the resulting developments in spacer materials have enabled high performance devices. The requirements of the 65 and 45 nm nodes stretch spike-annealing to its limit and newer Ultra-High Temperature anneals must be considered.

Improved stability in Al 2O 3CdSe thin-film transistors

AlAl 2O 3CdSe thin-film transistors have been fabricated that show significant improvement in electrical stability over previous devices reported. This improvement is shown to be due to the use of Al 2O 3 formed by plasma-anodization in a d.c. O 2 glow discharge. The use of this oxide as a gate insulator results in a two-orders-of-magnitude reduction in surface state density at the Al 2O 3CdSe improvement in electrical stability. Interface state densities are typically found to be less than 5 × 10 10 states/cm 2- eV. Transistors using Al 2O 3 have been bias-temperature tested at room temperature and up to 75°C. No shift in threshold voltage is presently observed at 75°C with gate oxide fields of 1 × 10 6 V/ cm. The use of Al 2O 3, while resulting in improved electrical stability, has not resulted in any loss of device performance. Thin-film transistors with gain-bandwidth product of 20 MHz and gate breakdown strengths of 7 × 10 6 V/cm are obtainable. Gate threshold voltages are typically 0−0.5 V. The effects of processing steps and the reproducibility of the transistors fabrication procedure have been studied. Through the use of post-deposition hydrogen annealing, excellent reproducibility in device characteristics has been achieved. Variations in transistor characteristics across a substrate are typically less than 10 per cent, while variation from substrate to substrate is also significantly reduced. The reduction is attributed to the low interface state density and the effects of annealing on oxide charge and CdSe resistivity.