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In the realm of energy harvesting, free-standing, film-type, moisture-driven electricity generators (MEGs) based on polymer hydrogels with moisture-retaining capability are promising as a convenient and practical power source, making them potentially suitable for various self-powered, wearable, and patchable electronic devices. Their performance is, however, substantially degraded under low-humidity (<40%) conditions owing to the limited water supply to the device. This study presents a high-performance film-type MEG that functions at a low humidity of 20%. The MEG is based on an ion-selective polymer aerogel as an electricity-generating layer, constructed on a water-collecting gel as a water reservoir. The water-collecting gel in the bi-layered MEG absorbs moisture even under low-humidity conditions and efficiently delivers moisture to the electricity-generating aerogel layer. The energy-harvesting ability of the electricity-generating aerogel layer is further facilitated by its characteristic vertical microstructure, which comprises aerogel pores directionally grown on the frozen water-collecting gel during the freeze-drying process. The low humidity-tolerant MEG generated a stable open-circuit voltage of 1.1 V for more than 500 min even under dry conditions (20% relative humidity). Various self-powered electronic applications are demonstrated with the low-humidity-tolerant, bi-layered MEGs in dry environments. This study provides new insights for designing future MEGs for operation in low-humidity environments, further facilitating the development of green and sustainable power generation. [Display omitted] • (Moisture-driven Energy Generators) MEGs offer a promising avenue for energy harvesting. • Most devices operate optimally only in high humidity environments. • With a water-absorbing layer and vertical aerogel, the MEG generate electricity even in low humidity conditions. • These MEGs are scalable and function as self-powered sensors for human activities. [ABSTRACT FROM AUTHOR]

• Anneal temperature for layer formation effect on carrier inter-diffusion phenomenon. • TEM/EDS analysis at carrier selective contact layer/interface oxide/substrate. • Comparison of free energy loss analysis by inter-diffusion depth and concentration. • Comparison of the overall output performance by interface quality and inter-diffusion. • Output characteristics with illumination, temperature and interface quality change. In this study, technology computer-aided design (TCAD) was used to investigate carrier selective contact solar cell performance based on the boundary of tunneling oxide and electron selective contact layer properties. The role of tunneling oxide quality in the passivation and inter-diffusion properties of the plasma-enhanced chemical vapor deposition of phosphorus-doped amorphous silicon as an electron selective contact layer is studied for carrier selective contact solar cells. Tunnel oxide quality varies according to the ratio of Si4+ to Si2+ state. For the Si4+/Si2+ ratio of 4, open-circuit voltage of 730 mV and the lowest interface trap density of 5.3 × 1010 cm−2 eV−1 are achieved. The change in diffusion depth of the doped layer with respect to the annealing temperature is analysed by transmission electron microscopy (TEM)/energy dispersive X-ray spectroscopy (EDS) measurement. Carrier selective contact solar cell parameters are optimized by incorporating the experimental values of interface trap density, inter-diffused impurity concentration, and depth in the Quokka 3 TCAD tool. Solar cell conversion efficiency of 24.31% was obtained. To understand the response of carrier selective solar cell to the environmental changes, the output characteristics of the solar cell were studied by varying the illumination temperature by 10% of the standard test conditions (STC) and temperature from 277 K to 377 K (difference of 100 K). [ABSTRACT FROM AUTHOR]

Abstract Visualization of human senses has been of great interest for developing an emerging interactive display that can artificially stimulate synesthesia with numerous unprecedented applications. Especially, visualization of various daily sound and music, which are much more complicated than human touch, in a form of flexible thin film devices can be a great challenge. We present flexible artificial synesthesia electronics that visualize continuous and complicated sounds. The electronic device is made of a thin composite film of a piezoelectric polymer for sound generation and inorganic electroluminescence (EL) microparticles for direct visualization of input sound signals. Field-induced EL of the microparticles in the device depends upon the source sound wave, making their EL synchronized with sound arising from the piezoelectric actuation. The flexible artificial synesthesia devices with sound-synchronized EL (FASSEL) showed extreme mechanical tolerance that can be repeatedly folded and crumpled with visible sound, allowing a variety of unexplored applications including synchronous sound-lightings and wearable, on-body sound-vision systems to facilitate emotional interaction of human being with sound in a human-friendly form. Graphical abstract Image 1 Highlights • Ultra-flexible piezoelectric loudspeakers were developed with sound synchronized EL. • Piezoelectric polymer composite with EL particles for direct visualization of sound. • Artificial synesthesia of sound and vision via a single capacitive device platform. • Silica-encapsulated-ZnS particle was employed for high EL with low leakage current. • Extreme mechanical tolerance that can be repeatedly folded and crumpled. [ABSTRACT FROM AUTHOR]

Ionic thermoelectric supercapacitors (ITESCs) produce orders of magnitude higher voltages than those of conventional thermoelectrics (TEs) based on the thermo-diffusion of electrons/holes and are therefore attractive for converting low-grade heat into electricity. The stretchability and stability of the whole ITESC are important for wearable heat harvesting applications. Recent studies on ITESC have focused on stretchable ionic TE electrolytes with a giant Seebeck coefficient, but there are no reports of fully stretchable ITESCs for wearable heat harvesting devices due to the lack of stretchable electrodes and stretchable ionic TE electrolytes with stability. Herein, we present a fully stretchable ITESC composed of stable high-performance ionic thermoelectric elastomer (ITE) electrolyte and stretchable gold nanowire (AuNW) electrodes. The ITE shows excellent air stability (> 60 d) in comparison to hydrogel-based electrolytes that are susceptible to dehydration in ambient conditions. Furthermore, the ITE exhibits an apparent thermopower up to 38.9 mV K–1 and ionic conductivity of 3.76 × 10–1 mS cm–1, which both are maintained up to a tensile strain of 250%. Finally, a fully stretchable ITESC with AuNW electrodes is developed which can harvest energy from thermal gradients during deformations. [Display omitted] • Ionic thermoelectric elastomer was made of polyethylene glycol diacrylate/2-hydroxyethyl acrylate network with ionic liquid. • The ITE shows excellent air and thermal stability in comparison to hydrogel-based electrolytes. • Thermopower (38.9 mV K–1) and ionic conductivity (3.76 × 10–1 mS cm–1) were obtained. • Ionic thermoelectric performances were maintained up to a tensile strain of 250%. • A stretchable ionic thermoelectric supercapacitor (ITESC) with the ITE and AuNW electrodes was developed. • The stretchable ITESC potentially offers a wearable heat harvesting device on the human epidermis. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENG) is of great interest as an emerging power harvester due to its simple device architecture and high efficiency. Despite development of various surface modification techniques for enhancing the performance of a TENG with a given triboelectric pair of materials, a method capable of being used universally on a variety of surfaces and improving the performance of TENGs with diverse surfaces remains a challenge. Here, we demonstrate a novel transfer-printing technique of hierarchically dewetted polymer droplets on various TENG surfaces for performance enhancement of the TENGs. Our method is based on controlled dewetting of a thin supramolecular assembled film of two end-functionalized polymer blends on a prepatterned poly(dimethyl siloxane) mold, followed by the physical pattern-transfer of arrays of the dewetted droplets consisting of supramolecular assembled nanostructures on a TENG contact surface. The hierarchically dewetted microdroplets comprising soft-etched nanopores efficiently improve the performance of a TENG by more than three times compared to one without the transferred pattern. The pattern-transfer is successfully achieved on various surfaces including not only oxides, plastics, rubbers, and metals, but also fabrics, coins, vegetables, and shells, making our approach a convenient way for enhancing the triboelectric performance of a given TENG. [ABSTRACT FROM AUTHOR]

Since the conventional fluorine-based electro-active polymers release toxic residues into the environment during their syntheses and decomposition processes, eco-friendly piezoelectric polymers are urgently demanded in the field of energy-related soft materials. Here, we derive a high-performance biodegradable chitin polymer from squid pen material and demonstrate its utility as a flexible piezoelectric material. The readily controlled ferroelectric chitin film confers excellent piezoelectricity under external mechanical pressure, resulting in comparable performance with that of conventional fluorine-based piezoelectric polymers. In particular, the sufficient piezoelectric behavior in chitin film allows us to not only realize a high-fidelity paper-type speaker and microphone that operates over a wide frequency range without significantly deteriorating the input and output sounds but also demonstrate transparent speaker consisting of AgNWs electrodes onto freestanding chitin film which also enables to resemble the original sound. Finally, the biodegradable chitin polymer can be successfully dissolved by chitinase enzyme within eight days without any toxic residues remained. [ABSTRACT FROM AUTHOR]

In this article we present a mechanism for creating metastable defects in intrinsic hydrogenated amorphous silicon (a-Si:H) layers by changing the flow-rate ratio of SiH 4 and H 2 . This is an important cardinal property that restricts the performance of both solar cells and thin-film transistors (TFT). Light or electrical bias results in generation of metastable dangling bonds. We evaluated the gas flow-rate ratio dependence of current decrease before and after application of electrical bias stress. Furthermore, we produced an a-Si:H TFT for comparison with a single-layer a-Si:H. Intrinsic layers deposited by SiH 4 to H 2 flow-rate ratios of 1:3 exhibited greater resistance to stress. In a-Si:H single layer experiment, we got a similar result, samples with SiH 4 and H 2 flow-rate ratios of 1:3 exhibited less decrease in current after application of electrical bias stress. These results will facilitate fabrication of more-stable a- Si:H thin film p-i-n solar cells. [ABSTRACT FROM AUTHOR]

Self-powered user-interactive displays that facilitate the visualization of human information acquired by sensors are of great interest in emerging human–machine interface technology with efficient energy consumption. Herein, a self-powered motion-sensing display capable of simultaneously detecting and visualizing finger motions is presented. Our device is based on a one-dimensional photonic crystal of an interpenetrated hydrogel network block copolymer (IHN-BCP) consisting of alternating water-absorbable and non-absorbable lamellae. Triboelectrification is achieved as a function of relative humidity from 30% to 80%. The direct visualization of the humidity is also achieved through the humidity-dependent structural color of the photonic crystal in the full visible range. Furthermore, the humidity-responsive triboelectrification and structural color of our IHN-BCP photonic crystal facilitates the development of a self-powered finger motion-sensing display where diverse gestures of a finger with natural humidity are quantitatively recognized, such as vertical and sliding motion of the finger with simultaneous visualization of the motions in both contact and non-contact modes. Self-powered finger motion-sensing display capable of simultaneously detecting and visualizing finger motions is developed, based on the one-dimensional photonic crystal of a self-assembled block copolymer. The humidity-responsive triboelectrification and structural color of our photonic crystal allows the quantitative sensing and visualization of diverse gestures of a finger with natural humidity. [Display omitted] • We demonstrate self-powered finger motion-sensing display based on self-assembled block copolymer photonic crystal • We utilize humidity-dependent triboelectrification and structural color of the photonic crystal in finger motion. • Self-powered triboelectric sensing is accomplished with simultaneous evolution of structural color in various finger motions. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on two main challenges: (i) to achieve a low surface recombination velocity and (ii) the quantitative control of the positive charges contained in the rear SiN x by varying the refractive index (n). We adopted a Si-rich SiN x film with a relatively thin thickness to control the fixed charge density (Q f ) from 2.74 × 1012 to 1.63 × 1012/cm2 and flat-band voltage (V FB ) is shifted from −2.53 to −1.41 V. A rear side recombination velocity (S rear) and implied open circuit voltage (iV oc ) was achieved 30 cm/s and 630 mV respectively after forming gas anneal (FGA) treatment. The low temperature processed LBC solar cell fabricated with photolithographic contacts exhibits V oc of 647 mV, and efficiency of 19.3%. The laser fired cell exhibits V oc of 637 mV, and efficiency of 19.0%. [Copyright &y& Elsevier]

Abstract: Industrial applicable fine-line double printing and nickel plating method was applied to single crystalline silicon (c-Si) solar cells. As the finger widths decreased, the efficiency and short circuit current density (J SC) linearly increased. Although the increase of the J SC was caused by the reduction of shadowing loss due to the decrease of finger width, the fill factor (FF) was slowly decreased due to increase of contact resistance. The FF of the cells using the fine line was enhanced by using a double printing and nickel plating. c-Si solar cells with the dimensions of 12.5cm×12.5cm, double printed finger width of 50μm due to spreadability of paste, a finger spacing of 2.4μm, and aluminum back surface field were fabricated, achieving an increase of J SC and efficiencies of up to about 0.62mA/cm2 and 0.38% compared to a reference cell at 79.8% of the FF, respectively. [Copyright &y& Elsevier]

Block copolymers (BCPs) have received great attention for the past 40 years but only within the past decade have they been seriously considered for nanotechnological applications. Their applicability to nanotechnology stems from the scale of the microdomains and the convenient tunability of size, shape, and periodicity afforded by changing their molecular parameters. The use of the tensorial physical properties of BCPs in such areas as transport, mechanical, electrical, and optical properties will provide substantial benefits in the future. In this review article, we first focus on the current efforts to utilize BCPs in nanotechnologies including nanostructured membranes, BCP templates for nanoparticle synthesis, photonic crystals, and high-density information storage media. In order to realize these applications, control over microdomain spatial and orientational order is paramount. This article reviews various methods to control BCP microdomain structures in the bulk state as well as in thin films. A variety of biases such as mechanical flow fields, electric fields, temperature gradients, and surface interactions can manipulate the microstructures of BCPs. A particular emphasis is made on two approaches, epitaxy and graphoepitaxy, and their combinations. Manipulation of BCP microdomain structures employing multiple external fields promises realization of many potential nanotechnological applications. [Copyright &y& Elsevier]

Controlled molecular and nanostructures of soft and hybrid materials are being studied for developing high-performance electronic devices such as solar cells, displays, memories, and sensors. Because these photoelectronic devices often consist of thin constituent layers of various soft and hybrid materials, conventional techniques, such as conduction, convection, and solvent vapor annealing—in which all constituent layers are exposed to heat and/or solvent source—are undesirable. The development of high-performance photoelectronic devices with controlled nanostructures of soft and hybrid materials requires alternative approaches that ensure a localized control of the nanostructures without harming the adjacent components. Recent advances in photon-assisted techniques based on photothermal conversion allow such localized control of the nanostructures of emerging materials. This review provides a comprehensive overview of the state-of-the-art photon-assisted technologies used to control the nanostructures of the emerging soft self-assembled materials, including self-assembled block copolymers, organic-inorganic halide perovskites, MOFs, and nanocomposites with a variety of low-dimensional nanomaterials of carbon nanotubes, graphenes, and transition metal dichalcogenides. Photothermal techniques involving light-to-heat conversion have been introduced, leading to the successful development of remotely and locally controlled nanostructures that are suitable for a variety of photoelectronic and electrochemical devices. Progressive device miniaturization and high-density integration such as lab-on-a-chip require novel techniques for controlling the nanostructures of constituent materials with minimal damage to adjacent components. In other words, techniques that ensure remote and local control of phase-separation, crystallization, curing/sintering, grafting, or crosslinking/scission of emerging soft and hybrid materials are in great demand. [Display omitted] • A comprehensive overview of photon-assisted nanostructures of emerging self-assembled soft materials is provided. • Recent progress with a focus on the compatibility between photon sources and light absorbing materials is presented. • Applications of structurally designed emerging materials including improvement and novel functionalities are summarized. [ABSTRACT FROM AUTHOR]

[Display omitted] van der Waals heterostructures (vdWHs), consisting of more than one type of atomically thin 2D crystal layers are emerging platforms for interesting electrical, optical, and catalytic applications. High yield production of vdWHs with atomic scale precision is crucial prerequisite for practical utilization. Here we present a generalized approach of random solution phase, high yield heteroassembly of semiconducting vdWHs by exploiting inherent surface charge states of 2D materials as well as chemical affinity of specific ligand end-functionalities. Facile removal of noncovalent functionalized ligands via simple pH reversal enables clean interfaces within vdWHs, yielding outstanding optoelectrical and electrochemical properties driven by fluent interfacial charge transfer among the layered 2D structures. The generality of this procedure is demonstrated by the formation of a series of different vdWHs such as WSe 2 -MoS 2 , graphene–MoS 2 - and phospherene–WSe 2 heterostructures. Atomically thin WSe 2 –MoS 2 phototransistor displayed an exceptionally fast response time with high sensitivity. Graphene–MoS 2 overcomes the inherent charge transfer issue of MoS 2 for electrochemical catalyst. Phospherene–WSe 2 successfully addresses poor ambient stability of phospherene together with enhanced surface activity towards chemical sensing. [ABSTRACT FROM AUTHOR]

Two dimensional (2D) p-MoTe 2 channel-based nonvolatile memory transistors with ferroelectric P(VDF-TrFE) polymer has been studied using a bottom-gate device architecture, which is introduced to dramatically reduce both of the switching and drain voltages to minimum 8 V and 10 mV, respectively. In fact, most of 2D-channel ferroelectric FETs with the same P(VDF-TrFE) polymer have used top-gate architectures, utilizing high switching pulse voltages over 20–25 V due to the existence of dead layer, which is unavoidably formed at the interface between P(VDF-TrFE) and thermal-deposited Al top gate. Key effects to realize such a low 8–13 V switching thus originate from the bottom-gate architecture. On the one hand, keys to obtain the low operation/drain voltage come from anneal-free Ohmic contact which is obtained using H 2 O 2 solution. Thanks to the low operation voltages of 10 mV, consuming power in the nonvolatile FETs can be minimized to ~a few pW for OFF/Erase state and ~a few hundred pW for ON/Program although it eventually becomes ~nW and ~30 nW for OFF and ON states in a practical circuit operation to switch organic light emitting diodes. Our approaches of bottom-gate architecture and H 2 O 2 contact nicely work even for transparent nonvolatile memory FET. ga1 • MoTe 2 channel memory transistor with P(VDF-TrFE) ferroelectric is fabricated. • Minimum switching voltage of 8 V is achieved from bottom-gate transistor architecture. • Ultralow operating voltage of 10 mV is achieved via H 2 O 2 treatment for source/drain contact. • Nanowatt power demonstration is performed with the memory transistor-integrated OLED pixel circuit. • Transparent ferroelectric memory transistor is also demonstrated. [ABSTRACT FROM AUTHOR]

Zn-polyiodide redox flow batteries (RFBs) are a promising grid-scale electrical energy storage (EES) option because of their significant energy density, which is due to the high solubility of ZnI 2 in water. In spite of the importance of the RFBs, a mechanistic understanding of both Zn2+/Zn and I 3 −/I− half redox reactions have not been fully achieved yet. The I 3 −/I− half redox reaction occurring on a cathode in this RFB is particularly complicated due to metastable iodine films, which only form on an electrode when an electrochemical potential is biased enough to drive the electro-oxidation of I−. Due to the thermodynamically unstable nature of iodine films in I−-rich aqueous solutions, the film is also difficult to characterize by ex-situ analyses, and its physicochemical properties are largely unknown. In this article, we report electrochemical in situ monitoring of the formation and dissolution of a metastable iodine film as an intermediate during I 3 −/I− redox reactions in an aqueous solution using a rotating ring disk electrode (RRDE). We suggested a reaction model for electro-oxidation of I− to I 3 − via iodine films and its electro-reduction to I− based on the mechanism proposed by Gileadi et al. Chronoamperograms (CAs) and cyclic voltammograms (CVs) associated with the I 2 /I− redox reaction involving only formation and dissolution of iodine films on a disk electrode were obtained using an RRDE. From the CAs and CVs, we successfully obtained trajectory information on the formation and dissolution of an iodine film during the I 3 −/I− redox reaction on a disk electrode under transient and potential-time variation conditions. In addition, we found evidence of a possible transition in the iodine film from an I−-conductor to an I−-semiconductor during formation based on the quantitatively monitored iodine formation curve as a function of time during electro-oxidation of I−. Image, graphical abstract [ABSTRACT FROM AUTHOR]

[Display omitted] Dual-mode optical encryption based on holographic metasurfaces and color components is of great attraction because of their enhanced information security and storage; however, the realization of independently as well as reversibly encodable holographic metasurfaces and color components remains unreported. Herein, we present reconfigurable dual-mode encryptions of structural colors (SC) and holograms, achieved through stimuli-responsive block copolymer (BCP) photonic crystals (PCs) with micro-imprinted holographic metasurfaces. Holographic images appear when the micro-imprinted BCP PCs, consisting of self-assembled alternating lamellae of two dielectrics, are exposed to an incident laser. A characteristic SC develops in the visible range when the imprinted film is immersed in a liquid agent that can swell one of the dielectrics, allowing for dual-mode holographic and SC encodings in the solid and liquid states, respectively. The dual-mode optical encoding is reconfigured. The holographic image can be erased and replaced with another micropattern, while preserving the SC. Moreover, an SC, set by crosslinking of the swellable lamellae, is reset by chemical de-crosslinking and subsequent transient re-crosslinking, enabling the SC reconfigurability of the BCP PC film. A prototype of a high-security reconfigurable dual encryption has been developed, wherein true information is decrypted when holographic passwords are confirmed with full-color visible SC passwords. [ABSTRACT FROM AUTHOR]

In this article, a classical redox mediated metal (in this study, Au) indicator electrode approach was revisited for the direct interrogation of 'slow' enzymatic redox second-order kinetics of horseradish peroxidase (HRP) for oxidative conversion of the model redox substrates, ferrocenemethanol (FcMeOH) and hydroquinone (H 2 Q) in low HRP-concentration levels. The presented electroanalysis allowed us to recognize the inhibited enzyme reactivity of HRP for FcMeOH-oxidation by its conjugation to model proteins (streptavidin, avidin, and monoclonal antibody), whereas this effect was negligible for H 2 Q-oxidation by HRP. From a theoretical investigation using finite element analysis, slow kinetics of HRP can be sensitively recognized through an Au indicator electrode approach in the case where HRP bulk electrolyzes a redox substrate in a solution. Five redox substrates were electrochemically investigated, and FcMeOH and H 2 Q showed negligible side reactions during mediation between HRP and the indicator electrode. From the chronoamperometric approach, the apparent rate constants for oxidative conversion of FcMeOH by the non-conjugated, free HRP were estimated to be ∼104 M−1s−1 at various pH values, while that of H 2 Q was roughly two orders of magnitude higher at pH ∼7. The molecular docking simulation revealed the need for a significant conformational change of HRP for FcMeOH access to the heme site, whereas the structural alternation of HRP was negligible for access of the H 2 Q into the domain of the enzyme. The simulation result indicates that the oxidative conversion rate of FcMeOH by HRP could be more susceptible to recognize additionally induced steric hindrance for access of the redox substrate to the catalytic site of the enzyme than that of H 2 Q. We experimentally verified that the apparent rate constant for FcMeOH-oxidation by the HRP conjugated to streptavidin was estimated to be ∼5 times smaller than that by the free HRP, and those by other conjugates to avidin and monoclonal antibody were ∼60% of that by the non-conjugated one. In contrast to the case of FcMeOH, the estimated reactivity of H 2 Q by HRP was barely affected by the conjugated model proteins. The presented study demonstrated that a redox enzymatic reactivity of HRP could be significantly affected by conjugated proteins when access of a redox substrate to a catalytic site of an enzyme is susceptible to conformational changes. [Display omitted] [ABSTRACT FROM AUTHOR]

Here we report a new nanogap formation manner at edges of a palladium (Pd) thin film on highly patterned arrays of an elastomeric PDMS substrate fabricated nanoimprint lithography (NIL) by absorption/desorption cycles of H 2 for use in the detection of hydrogen (H 2 ) gas. A 10-nm-thick Pd layer was deposited on the patterned PDMS substrate using an ultra-high vacuum DC magnetron sputtering system. The Pd nanogaps (∼100 nm (W)) formed on the edges of the grating structure by expansion and contraction of the film through a few cycles of H 2 absorption and desorption. Such nanogaps are crucial to the performance of the sensors. The H 2 sensors were found to exhibit a fast response time (∼1 s), low detection limit (0.1%), wide linear range (0.1–2%), and an ON–OFF switching operation in air. These properties are attributed to the synergistic combination of nanogap break junction control in Pd and the patterned elastomeric substrate. [ABSTRACT FROM AUTHOR]

Abstract: The surface passivation is one of the crucial steps to achieve high conversion efficiencies in c-Si solar cells. Though thermal silicon oxide (SiO2) and silicon nitride (SiN x ) provides a good passivation layer the high temperature process of SiO2 and the fixed positive charge of SiN x on p-substrate cause detrimental effect in surface passivation. A thermally stable thin film with a negative charge (for p-substrate) passivation layer is required to develop a good rear passivation suitable for PERC cells processed with screen printing. In this paper, a PECVD stack layer system consisting of SiO x , SiN x , and SiO x was employed for rear side passivation. The optimal refractive index of silicon oxide and silicon nitride thin film was found by varying the silane, ammonia and nitrous oxide gas ratios. A low surface recombination velocity (SRV) was achieved using interface treatment. Carrier lifetime of 212 μs and interface trap density of 8.265 × 109 cm−2 eV−1 was obtained. With optimized PECVD–ONO layer, the solar cell parameters measured were V OC of 647 mV and efficiency of 19.3%, while those of the reference solar cell were V OC of 621 mV and efficiency of 18.6%. [Copyright &y& Elsevier]

Abstract: Micropatterning of a semicrystalline poly(vinylidene fluoride) (PVDF) solution was performed by a temperature controlled capillary micromolding where the rate of solvent evaporation was controlled by substrate temperature. In order to choose proper solvents for micropatterning, we have investigated the solubility of PVDF in various organic solvents and crystal structures of the PVDF bulk films cast from the solvents. The films prepared from the polar solvents such as dimethylformamide (DMF), dimethyl sulfoxide (DMSO) dominantly showed γ type crystals regardless of preparation temperature, while the films from tetrahydrofuran (THF) exhibit α type crystals and the ones from acetone and methyl ethyl ketone (MEK) show the characteristics of both α- and γ-PVDF. The quality of micropatterns and shapes of the PVDF crystals in the patterns significantly depend on solvent evaporation rates. Micropatterns of PVDF formed in DMF at 120°C showed the best uniformity in shape. Crystals of the PVDF nucleated at the center regions of microchannels tended to be elongated with the b-axis of γ-PVDF crystals along the channels as the concentration of the solution decreased. In contrast, crystals nucleated at the corner regions of the channels had their b-axis oriented perpendicular to the channels. In line patterns with the width of 2μm, the corner nucleated crystals were dominant and a resulting bamboo-like crystalline microstructure was observed in which the b-axis of γ-PVDF crystals, fast growth direction, is oriented normal to the microchannels. The crystal structures of the bulk films and the micropatterns were characterized by X-ray diffractometer, Fourier transform infrared spectroscope in Attenuated Total Reflection mode, Polarized Optical and Scanning Electron Microscope. [Copyright &y& Elsevier]

It has been believed that stereo-irregular polymers hardly form crystalline structure because of the deficient ordering along the backbone direction. Here we show the crystallization of atactic polymers by rapid thermal quenching of polymers co-melted with a chain-stretching agent. To this end, crystalline PMMAs (hc-PMMAs) are prepared from stereo-irregular atactic-PMMAs (M n = 35–1500 kg/mol) as well as stereo-regular isotactic- and syndiotactic-PMMAs by rapid quenching of molten PMMA/benzoic acid (BA) solutions. BA acts as a chain-stretching agent. PMMA chains are elongated up to 60% of their contour length when they are co-melted with BA. The preferential hydrogen bonding between PMMA and BA compensates the conformational entropy loss of PMMA chains in molten PMMA/BA solutions. Upon quenching, PMMA chains are further stretched because of the large tensile stress induced by the sudden temperature drop and because of mechanical squeezing by concomitant directional crystallization of anisotropic lath-like BA crystals. After sublimation of BA, the PMMA shows a clear melting transition: T m = 276–283 °C for hc- s -PMMA and 293–306 °C for hc- a -PMMA. Unlike other conventional crystals having 3D crystallinity, hc-PMMAs exhibits 1D crystallinity due to ordered lateral packing between chains (d = ∼4.3 Å) which is independent on the tacticity while the packing is amorphous-like for the other two directions. For the reason of the reduced dimensionality in crystallinity, we named the crystalline PMMA as 1D hypo-crystalline PMMA (hc-PMMA). Because of their high 1D crystallinity (55–65%), hc-PMMAs exhibit the storage modulus (E ′) enhanced by 20 times comparing with those of pristine PMMA. [ABSTRACT FROM AUTHOR]

Electron-hole pair (EHP) recombination is a decreasing factor of the efficiency in silicon solar cells. The passivation layer reduces recombination by removing dangling bonds which act as recombination centers. Usually, SiN x , SiO x , SiON x and AlO x layers are used as passivation layer in solar cell applications. Tunnel oxide layer is one of the main issues to achieve high-quality passivation using carrier-selectivity between the silicon wafer and poly-Si layer. In this work, ultra-thin tunnel oxide layer by plasma enhanced chemical vapor deposition using N 2 O plasma is deposited on both sides of the samples. The RF power and substrate temperature are varied. Then phosphorus doped Si layer is deposited. The optimized tunnel oxide layer has low D it (5.3 × 10 10 cm −2 eV −1 ) and high passivation effect (τ eff of 923 μs, iV oc of 739 mV) when deposited with RF power of 200 W and a substrate temperature of 400 °C. This optimized tunnel oxide passivation layer is applied to the n-type c-Si solar cell. The fabricated solar cell showed J sc of 41.04 mA/cm 2 and V OC of 644 mV. Compared to the cell with chemical oxide passivation, J sc and V oc increased by 0.2 mA/cm 2 and 11 mV which were also higher than the cell with SiN x passivation. [ABSTRACT FROM AUTHOR]

In this study, highly anisotropic Cu oblate ellipsoids incorporated polymer composites were prepared that revealed excellent broadband electromagnetic shielding effectiveness of 80.0 to 62.1 dB at a frequency region between 300.0 KHz and 12.0 GHz, at low Cu contents. Cu-coated hollow polymer beads were fabricated through electroless plating of Cu on the polymer hollow beads. The hollow polymer beads were prepared through thermal expansion of acrylonitrile-based polymer beads containing a blowing agent. These beads were capable of incorporating highly anisotropic 2-dimensional (2D) Cu oblate ellipsoids into polymer composite through simple compression molding process. The resulting broadband electromagnetic shielding performance attributes to a low percolation behavior of the composites due to high anisotropy of the conductive Cu filler and their multilayered structure in the composites. [ABSTRACT FROM AUTHOR]

The phase transitions in the films of an asymmetric polystyrene- b -poly(2-vinylpyridine) (PS- b -P2VP) were investigated by grazing incidence small-angle X-ray scattering (GISAXS) and transmission electron microscopy (TEM). Compared with the sequential transitions in the bulk, hexagonally perforated layer (HPL) – gyroid (GYR) – disorder (DIS) upon heating, the transitions in film geometry were dramatically changed with decreasing thickness due to the growing preferential interactions from substrate, resulting in a thickness-dependent transition diagram including four different morphologies of hexagonally modulated layer (HML), coexisting (HML and GYR), GYR, and DIS. Particularly in the films ≤10 L o , where L o is d -spacing at 150 °C, a stable HML structure was identified even above the order-to-disorder transition (ODT) temperature of the bulk, which was attributed to the suppressed compositional fluctuations by the enhanced substrate interactions. [ABSTRACT FROM AUTHOR]

In this study, we propose a statistical approach based on Taguchi method and Grey relational analysis for effective optimization of indium tin oxide (ITO) films which are used as front contact for shallow emitter based crystalline silicon (c-Si) solar cells. The experiments were designed by the Taguchi method through an orthogonal array, resulting in the reduction of the number of experiments by approximately 90%; the reproduction effect of process parameters on performance characteristics, however, is still ensured. Excellent compromise between electrical and optical properties of ITO films was obtained by Grey relational analysis at power density of 0.685W/cm2, working pressure of 0.4Pa, substrate temperature of 250°C, and post-annealing temperature of 300°C in 30min. The ITO films exhibited lowest electrical resistivity of 1.316×10−4 Ωcm, and highest transmittance of 91.251% under optimal condition. The shallow emitter based c-Si solar cells using the optimal ITO films showed highest efficiency of 17.555%, yielding a 1.375% absolute increase in efficiency compared to using ITO films with initial condition. Furthermore, using analysis of variance, we found that the substrate temperature was a key parameter which critically affected the opto-electrical properties of ITO films. [ABSTRACT FROM AUTHOR]

Abstract: Local Back Contact (LBC) crystalline silicon solar cell with novel antimony (Sb) Local Back Surface Field (LBSF) are reported. The Sb LBSF is formed at low temperature with a Laser Fired Contacts (LFC) process. To improve the solar cell parameters of Sb LBSF, the rear passivation layer with SiN x is optimized by varying the refractive index. The Si-rich SiN x with a refractive index (n) of 2.7 possesses high lifetime of 2 ms with reduced absorption at a longer wavelength. The increase in lifetime is analyzed with Si–H bond concentration by FTIR. A 100 nm thick Sb layer with low laser power of 44 mW resulted in a junction depth of 500 nm with a carrier concentration of 5 × 1020 cm−3. The improved rear passivation with Si-rich SiN x , the optimized Sb thickness yielded the best electrical results, with open circuit voltage (V oc) of 643 mV and efficiency of 19.25%, compared to the reference cell with V oc of 625 mV and efficiency of 18.20%. [Copyright &y& Elsevier]

Abstract: We report n-type passivated emitter rear totally diffused (PERT) silicon solar cells with local back contacts (LBC) formed by laser process. With passivated back surface field (BSF), the PERT cell design shows an improved open circuit voltage (V oc) with reduced recombination at the rear due to improved optical confinement. The rear side was diffused by POCl3 diffusion with low sheet resistance (R s) BSF and passivated using SiN x . Laser ablation was used to open the SiN x on the rear for LBC. The Nd:YAG laser power (mW) parameters and POCl3 doping temperature were varied to obtain the BSF with lower sheet resistance. Laser power of 44 mW with 10 kHz resulted in 30 Ω/sq BSF layer with effective lifetime (τ eff) of 90 μs and a higher V oc of 646 mV. With the optimized laser parameters the best electrical results yielded a short circuit current density (J sc) of 36 mA/cm2 and efficiency of 18.54%. [Copyright &y& Elsevier]

We report on a laser-doping process for the formation of a local back surface field with antimony for n-type crystalline silicon solar cells. The local back surface field was formed at low temperature with a laser-fired contact process. A 100nm thick Sb layer with 44mW laser power resulted in a junction depth of 500nm, and a carrier concentration of 5×1020 cm−3 yielded the best electrical results, with a current density of 35mAcm−2 and an efficiency of 17.16%. [Copyright &y& Elsevier]

Abstract: This paper presents an acidic texturing and a novel vapor texturing method for Edge-defined Film-fed Growth (EFG) multi-crystalline silicon (mc-Si) wafers. P-type EFG mc-Si wafers with resistivity 0.5–2Ωcm and thickness of 300±70μm were textured with acidic solution using HF:HNO3:CH3COOH. The reflectance decreased as the acid etching proceeded and then saturated when the etching depth reached 10μm. The isotropic etching of acid texturing resulted in minimum reflectance of 13%. For vapor texturing, the vapor particles were generated by adding silicon to HF:HNO3 acidic solution. Initially silicon was oxidized with HNO3 vapor particles. The nano-pore sized ion formed over the EFG mc-Si wafer acted as a barrier on the Si surface. The HF vapor particles then dissolved the formed SiO2 effectively by passing through the nano-pores of ion and etched the EFG mc-Si wafer. The anisotropic etching of vapor textured wafers resulted in an etching depth of about 2.78μm with reflectance of 5%. The EFG mc-Si solar cell fabricated with acid texturing had V OC of 592mV, J SC of 27.71mA/cm2 and efficiency of 12.85% while the cell with novel vapor texturing showed V OC of 597mV, J SC of 29.61mA/cm2 and efficiency of 13.54%. [Copyright &y& Elsevier]

Abstract: In this study, we demonstrate control over the localized surface plasmon band (SPB) of a micellar poly(styrene-block-4vinylpyridine) (PS-b-P4VP) copolymer thin film composite that includes Ag and Au nanoparticles (NPs) in the presence of single walled carbon nanotubes (SWCNTs). Ag and Au NPs are preferentially located in the P4VP core and the PS corona of ordered spherical PS-b-P4VP copolymer micelles, respectively. This structure gave rise to a single SPB due to the coupling of Ag and Au SPBs. The non-covalent addition of SWCNTs in the block copolymer micelles shifts the coupled SPB to a lower wavelength. The maximum shift in the coupled SPB of approximately 30nm was achieved in the PS-b-P4VP/Ag/Au NPs composite. The carbon nanotube induced modulation of the coupled SPB stems from the charge accumulation effect of the SWCNTs placed between the two types of nanoparticles. [Copyright &y& Elsevier]

Abstract: A new polymeric amphiphilic molecule for dispersing carbon nanotubes (CNTs) in water, oligothiophene-terminated poly(ethylene glycol) (TN-PEG), was synthesized and its ability to stabilize aqueous CNT dispersions was examined by UV–Vis spectroscopy and transmission electron microscopy. It was observed that the TN-PEGs were strongly adsorbed onto the nanotube surface via a strong π–π interaction, and thus only gentle sonication causes exfoliation of CNT ropes and bundles into well-separated individual objects and small bundles comprising 2–10 tubes. The dispersion ability of the TN-PEGs and the long-term stability of their resulting dispersions were much better than commercial surfactants. [Copyright &y& Elsevier]

Abstract: Microstructures of hundreds of micron thick poly(styrene-block-isoprene) copolymer films solution-cast in a cylindrical tube with the solvent evaporation controlled were investigated by transmission electron microscope (TEM), small angle X-ray scattering (SAXS) and optical microscope (OM). In a block copolymer with cylindrical polyisoprene microdomains, the orientation of the cylinders was varied along radial direction of the cylindrical tube. Highly aligned hexagonal arrays of in-plane polyisoprene cylinders were formed with their cylindrical axis parallel to the circumference of the tube in the regimes close to the wall edge. In contrast randomly ordered microdomains were observed at the center of the tube. We have also found that the orientation depends on the solvent evaporation rate and an intermediate rate (∼2.3nL/s) provides the best orientation. In the case of a block copolymer with a bicontinuous double gyroid structure, we obtained a globally ordered microstructure where [111] crystallographic direction was parallel to the circumference of the tube. For both block copolymers, the area of highly ordered arrays of nanoscopic domains is over 1mm2. Development of the orientation was explained by coupling two orthogonal fields: (1) The flow of a solution induced by strong capillary force at a meniscus between the cylindrical tube wall and the block copolymer solution and (2) the solvent evaporation. [Copyright &y& Elsevier]