Impedance spectroscopy of Sb₂Se₃ photovoltaics consisting of (Sb₄Se₆)_<i>n</i> nanoribbons under light illumination.

Sb2Se3, consisting of one-dimensional (Sb4Se6)n nanoribbons has drawn attention as an intriguing light absorber from the photovoltaics (PVs) research community. However, further research is required on the performance-limiting factors in Sb2Se3 PVs. In this study, we investigated the charge carrier behavior in Sb2Se3 PVs by impedance spectroscopy (IS) under light illumination. (Sb4Se6)n nanoribbons with two different orientations were used to investigate the effect of crystal orientation on the device performance. Regardless of the (Sb4Se6)n orientation, negative capacitance was observed at forward bias, representing a recombination pathway at the TiO2/Sb2Se3 interface. A comparison of the recombination resistances and lifetimes of two different Sb2Se3 PVs showed that a better interface could be formed by placing the (Sb4Se6)n ribbons parallel to the TiO2 layer. Based on these observations, an ideal structure of the Sb2Se3/TiO2 interface is proposed, which will enhance the performance of Sb2Se3 PVs toward its theoretical limit

Highly Reliable Magnetic-based Pressure Sensor utilizing Simple Microstructured PDMS: Mechanical and Design Analysis via Finite Element Analysis

Pressure sensors have been integral in the development of biomedical industry and health monitoring devices. Their versatility in applications as well as their simple, straightforward mechanisms have led to massive production of pressure sensors which are typically based on the electrical properties of the active materials. This, however, introduces some risks in the sensors&amp;#x2019; reliability due to difficulties in maintaining the materials&amp;#x2019; uniformity. To address this issue, a unique magnetic-based pressure sensor is fabricated utilizing a planar Hall resistive (PHR) sensor, a magnet and simple microstructured polydimethylsiloxane (PDMS) layers fabricated via 3D printed molds. The stability of the magnetic sensor and its incredibly small hysteresis value ensure high reproducibility. Furthermore, the PDMS layers are further fine-tuned and their deformation analyzed using finite element method. This analysis offers insight into the mechanism of PDMS compression as well as provide clues on further improvisations of the pressure sensor. The successful integration of the magnetic-based pressure sensor into health monitoring processes such as pulse monitoring, respiration and phonetic recognition also promises its wide expanse of possibilities as a wearable diagnostic device. IEEE1

Highly Transparent Low Resistance ZnO/Ag Nanowire/ZnO Composite Electrode for Thin Film Solar Cells

We present an indium-free transparent conducting composite electrode composed of silver nanowires (AgNWs) and ZnO bilayers. The AgNWs form a random percolating network embedded between the ZnO layers. The unique structural features of our ZnO/AgNW/ZnO multilayered composite allow for a novel transparent conducting electrode with unprecedented excellent thermal stability (∼375 °C), adhesiveness, and flexibility as well as high electrical conductivity (∼8.0 Ω/sq) and good optical transparency (>91% at 550 nm). Cu(In,Ga)(S,Se)₂ (CIGSSe) thin film solar cells incorporating this composite electrode exhibited a 20% increase of the power conversion efficiency compared to a conventional sputtered indium tin oxide-based CIGSSe solar cell. The ZnO/AgNW/ZnO composite structure enables effective light transmission and current collection as well as a reduced leakage current, all of which lead to better cell performance

Uniform Pressing Mechanism in Large-Area Roll-to-Roll Nanoimprint Lithography Process

We aimed to increase the processing area of the roll-to-roll (R2R) nanoimprint lithography (NIL) process for high productivity, using a long roller. It is common for a long roller to have bending deformation, geometric errors and misalignment. This causes the non-uniformity of contact pressure between the rollers, which leads to defects such as non-uniform patterning. The non-uniformity of the contact pressure of the conventional R2R NIL system was investigated through finite element (FE) analysis and experiments in the conventional system. To solve the problem, a new large-area R2R NIL uniform pressing system with five multi-backup rollers was proposed and manufactured instead of the conventional system. As a preliminary experiment, the possibility of uniform contact pressure was confirmed by using only the pressure at both ends and one backup roller in the center. A more even contact pressure was achieved by using all five backup rollers and applying an appropriate pushing force to each backup roller. Machine learning techniques were applied to find the optimal combination of the pushing forces. In the conventional pressing process, it was confirmed that pressure deviation of the contact area occurred at a level of 44%; when the improved system was applied, pressure deviation dropped to 5%

High-resolution printing of micrometer-scale copper electrode: From ink formulation and process optimization to application

In the rapidly advancing field of electronics, there is a growing demand for devices to be miniaturized with high-resolution patterns and compact, straightforward configurations, all while maintaining cost competitiveness. Precision patterning of conductive nano ink based on inexpensive metals offers an effective solution. This technique has proven compatibility with numerous integrated electronics. However, conventional patterning techniques face difficulties achieving high resolution, uniform thickness, and compatibility with environments prone to oxidation. Here, we optimize the reverse offset printing process and its ink formulation for green manufacturing of high-quality, high-resolution conductive micropatterns. The oleate ligand on the surface of Cu nanoparticles (CuNPs) is replaced by polyvinylpyrrolidone, which is more suitable for the steric stabilization of CuNPs in eco-friendly, polar solvent. Then, in consideration of the reverse offset printing mechanism, solvents and additives are evaluated to prepare a reverse offset printable ink. By examining the change in printability according to the composition and process parameters, we determine the printable composition range and process conditions. High-quality CuNP micropatterns with a fine line width of 10 μm, narrow spacing, sharp edge definition, and high uniformity are achieved. Finally, the reverse offset printed CuNP micropatterns are successfully implemented in thermistor microarrays as a potential application. © 2023 The AuthorsTRU

High-Resolution and Large-Area Patterning of Highly Conductive Silver Nanowire Electrodes by Reverse Offset Printing and Intense Pulsed Light Irradiation

Conventional printing technologies such as inkjet, screen, and gravure printing have been used to fabricate patterns of silver nanowire (AgNW) transparent conducting electrodes (TCEs) for a variety of electronic devices. However, they have critical limitations in achieving micrometer-scale fine line width, uniform thickness, sharp line edge, and pattering of various shapes. Moreover, the optical and electrical properties of printed AgNW patterns do not satisfy the performance required by flexible integrated electronic devices. Here, we report a high-resolution and large-area patterning of highly conductive AgNW TCEs by reverse offset printing and intense pulsed light (IPL) irradiation for flexible integrated electronic devices. A conductive AgNW ink for reverse offset printing is prepared by carefully adjusting the composition of AgNW content, solvents, surface energy modifiers, and organic binders for the first time. High-quality and high-resolution AgNW micropatterns with various shapes and line widths are successfully achieved on a large-area plastic substrate (120 × 100 mm 2 ) by optimizing the process parameters of reverse offset printing. The reverse offset printed AgNW micropatterns exhibit superior fine line widths (up to 6 μm) and excellent pattern quality such as sharp line edge, fine line spacing, effective wire junction connection, and smooth film roughness. They are post-processed with IPL irradiation, thereby realizing excellent optical, electrical, and mechanical properties. Furthermore, flexible OLEDs and heaters based on reverse offset printed AgNW micropatterns are successfully fabricated and characterized, demonstrating the potential use of the reverse offset printing for the conductive AgNW ink. © 2019 American Chemical Society.FALS

A Hierarchical Metal Nanowire Network Structure for Durable, Cost-Effective, Stretchable, and Breathable Electronics

Polymer nanofiber-based porous structures ("breathable devices") have been developed for breathable epidermal electrodes, piezoelectric nanogenerators, temperature sensors, and strain sensors, but their applications are limited because increasing the porosity reduces device robustness. Herein, we report an approach to produce ultradurable, cost-effective breathable electronics using a hierarchical metal nanowire network and an optimized photonic sintering process. Photonic sintering significantly reduces the sheet resistance (16.25 to 6.32 ω sq-1) and is 40% more effective than conventional thermal annealing (sheet resistance: 12.99 ω sq-1). The mechanical durability of the sintered (648.9 ω sq-1) sample is notably improved compared to that of the untreated (disconnected) and annealed (19.1 kω sq-1) samples after 10,000 deformation cycles at 40% tensile strain. The sintered sample exhibits ∼29 times less change in electrical performance compared to the thermally annealed sample. This approach will lead to the development of affordable and ultradurable commercial breathable electronics. © 2021 American Chemical Society.FALS

Roll-to-roll-compatible, flexible, transparent electrodes based on self-nanoembedded Cu nanowires using intense pulsed light irradiation

Copper nanowire (Cu NW)-based flexible transparent conductive electrodes (FTCEs) have been investigated in detail for use in various applications such as flexible touch screens, organic photovoltaics and organic light-emitting diodes. In this study, hexadecylamine (HDA) adsorbed onto the surface of NWs is changed into polyvinylpyrrolidone (PVP) via a ligand exchange process; the high-molecular-weight PVP enables high dispersion stability. Intense pulsed light (IPL) irradiation is used to remove organic species present on the surface of the NWs and to form direct connections between the NWs rapidly without any atmospheric control. NWs are self-nanoembedded into a plastic substrate after IPL irradiation, which results in a smooth surface, strong NW/substrate adhesion, excellent mechanical flexibility and enhanced oxidation stability. Moreover, Cu NW FTCEs with high uniformities are successfully fabricated on a large area (150 mm × 200 mm) via successive IPL irradiation that is synchronized with the motion of the sample stage. This study demonstrates the possibility of roll-to-roll-based, large-scale production of low-cost, high-performance Cu NW-based FTCEs. © The Royal Society of Chemistry 2016.

Meyer-Rod Coated 2D Single-Crystalline Copper Nanoplate Film with Intensive Pulsed Light for Flexible Electrode

Copper is widely used because it is inexpensive, abundant, and highly conductive. However, most copper used in industrial coating processes is in the form of circular powder, which is problematic for large area, high conductive coatings. In this work, 2D single-crystalline Cu nanoplates (Cu NPLs) were synthesized and a systematic study on coating with large-scale Cu NPLs using a Meyer-rod coating process was performed. The rheological behaviors of the Cu solution with various concentrations, surface tensions, and speeds were analyzed using Ca and Re numbers to optimize coating conditions. In addition, the effect of intensive pulse light (IPL) to sinter the coper film within a 1 s timeframe was also investigated in order to be able to produce an electrode in the shortest possible time which is applicable to industry. Finally, the Meyer-rod coated electrode was utilized in an electrochemical luminescence (ECL) device