Analogous Design of a Microlayered Silicon Oxide-Based Electrode to the General Electrode Structure for Thin-Film Lithium-Ion Batteries.

Development of miniaturized thin-film lithium-ion batteries (TF-LIBs) using vacuum deposition techniques is crucial for low-scale applications, but addressing low energy density remains a challenge. In this work, structures analogous to SiOx-based thin-film electrodes are designed with close resemblance to traditional LIB slurry formulations including active material, conductive agent, and binder. The thin-film is produced using mid-frequency sputtering with a single hybrid target consisting of SiOx nanoparticles, carbon nanotubes, and polytetrafluoroethylene. The thin-film SiOx/PPFC (plasma-polymerized fluorocarbon) involves a combination of SiOx and conductive carbon within the PPFC matrix. This results in enhanced electronic conductivity and superior elasticity and hardness in comparison to a conventional pure SiOx-based thin-film. The electrochemical performance of the half-cell consisting of thin-film SiOx/PPFC demonstrates remarkable cycling stability, with a capacity retention of 74.8% up to the 1000th cycle at 0.5 C. In addition, a full cell using the LiNi0.6Co0.2Mn0.2O2 thin-film as the cathode material exhibits an exceptional initial capacity of ≈120 mAh g-1 at 0.1 C and cycle performance, marked by a capacity retention of 90.8% from the first cycle to the 500th cycle at a 1 C rate. This work will be a stepping stone for the AM/CB/B composite electrodes in TF-LIBs.

Light-Emitting Transistors with High Color Purity Using Perovskite Quantum Dot Emitters.

The class of organic-inorganic lead halides with perovskite crystal structures has recently emerged as promising materials for a variety of practical optoelectronic applications. In particular, hybrid halide perovskite quantum dots possess excellent intrinsic optoelectronic properties such as high color purity (full width at half-maximum of 24.59 nm) and photoluminescence quantum yields (92.7%). In this work, we demonstrate the use of perovskite quantum dot materials as an emissive layer of hybrid light-emitting transistors. To investigate the working mechanism of perovskite quantum dots in light-emitting transistors, we investigated the electrical and optical characteristics under both p-channel and n-channel operation. Using these materials, we have achieved perovskite quantum dot light-emitting transistors with high electron mobilities of up to 12.06 cm2·V-1 s-1, high brightness of up to 1.41 × 104 cd m-2, and enhanced external quantum efficiencies of up to 1.79% operating at a source-drain potential of 40 V.

Tungsten-Doped Zinc Oxide and Indium-Zinc Oxide Films as High-Performance Electron-Transport Layers in N-I-P Perovskite Solar Cells.

Perovskite solar cells (PSCs) have attracted tremendous research attention due to their potential as a next-generation photovoltaic cell. Transition metal oxides in N-I-P structures have been widely used as electron-transporting materials but the need for a high-temperature sintering step is incompatible with flexible substrate materials and perovskite materials which cannot withstand elevated temperatures. In this work, novel metal oxides prepared by sputtering deposition were investigated as electron-transport layers in planar PSCs with the N-I-P structure. The incorporation of tungsten in the oxide layer led to a power conversion efficiency (PCE) increase from 8.23% to 16.05% due to the enhanced electron transfer and reduced back-recombination. Scanning electron microscope (SEM) images reveal that relatively large grain sizes in the perovskite phase with small grain boundaries were formed when the perovskite was deposited on tungsten-doped films. This study demonstrates that novel metal oxides can be used as in perovskite devices as electron transfer layers to improve the efficiency.

Significant enhancement of the bias stability of Zn-O-N thin-film transistors via Si doping.

Si doping was used to significantly improve the bias stability of ZnON thin-film transistors. Si 3 W (~1%) doped ZnON TFTs showed a saturation mobility of 19.70 cm2/Vs along with remarkable improvements in the threshold voltage shift for negative gate bias stress (NBS) within 1.69 V. The effects of Si doping were interpreted by the experimental correlation between device performance and physical analysis, as well as by the theoretical calculation. Si doping induces the reduction of N-related defects by increasing stoichiometric Zn3N2, and decreasing nonstoichiometric ZnxNy. In addition, Si doping reduces the band edge states below the conduction band. According to density functional theory (DFT) calculations, Si, when it substitutes for Zn, acts as a carrier suppressor in the ZnON matrix.

Material Design of New p-Type Tin Oxyselenide Semiconductor through Valence Band Engineering and Its Device Application.

This paper reports a new p-type tin oxyselenide (SnSeO), which was designed with the concept that the valence band edge from O 2p orbitals in the majority of metal oxides becomes delocalized by hybridizing Se 4p and Sn 5s orbitals. As the Se loading increased, the SnSeO film structures were transformed from tetragonal SnO to orthorhombic SnSe, which was accompanied by an increase in the amorphous phase portion and smooth morphologies. The SnSe0.56O0.44 film annealed at 300 °C exhibited the highest Hall mobility (µHall), 15.0 cm2 (V s)-1, and hole carrier density (nh), 1.2 × 1017 cm-3. The remarkable electrical performance was explained by the low hole effective mass, which was calculated by a first principle calculation. Indeed, the fabricated field-effect transistor (FET) with a p-channel SnSe0.56O0.44 film showed the high field-effect mobility of 5.9 cm2 (V s)-1 and an ION/OFF ratio of 3 × 102. This work demonstrates that anion alloy-based hybridization provides a facile route to the realization of a high-performance p-channel FET and complementary devices.

Universal Route to Impart Orthogonality to Polymer Semiconductors for Sub-Micrometer Tandem Electronics.

A universal method that enables utilization of conventional photolithography for processing a variety of polymer semiconductors is developed. The method relies on imparting chemical and physical orthogonality to a polymer film via formation of a semi-interpenetrating diphasic polymer network with a bridged polysilsesquioxane structure, which is termed an orthogonal polymer semiconductor gel. The synthesized gel films remain tolerant to various chemical and physical etching processes involved in photolithography, thereby facilitating fabrication of high-resolution patterns of polymer semiconductors. This method is utilized for fabricating tandem electronics, including pn-complementary inverter logic devices and pixelated polymer light-emitting diodes, which require deposition of multiple polymer semiconductors through solution processes. This novel and universal method is expected to significantly influence the development of advanced polymer electronics requiring sub-micrometer tandem structures.

Effect of counter-ions on the properties and performance of non-conjugated polyelectrolyte interlayers in solar cell and transistor devices.

We have investigated a series of non-conjugated polyelectrolytes (NPEs) which are based on a polyethylenimine (PEI) backbone with various counterions, such as Br- I- and BIm4 -, as interfacial layers at the electrodes of solar cells and transistor devices to improve the power conversion efficiency (PCE) and device performance. This new series of NPEs with different counterions are capable of forming electric dipoles at NPE/metal electrode interfaces; as a consequence tuning of the energy levels, and work function (WF) of the electrodes is possible. Using this approach, the PCE of organic solar cells could be improved from 1.05% (without NPEs) to 6.77% (with NPEs) while the charge carrier mobility and on/off ratio of FET devices could be improved, showing the broad utility of this type of material. This study provides a novel approach towards investigating the influence of ions on interfacial dipoles and electrode WFs in solution-processed semiconducting devices.

Replacement of n-type layers with a non-toxic APTES interfacial layer to improve the performance of amorphous Si thin-film solar cells.

Hydrogenated amorphous Si (a-Si:H) thin-film solar cells (TFSCs) generally contain p/n-type Si layers, which are fabricated using toxic gases. The substitution of these p/n-type layers with non-toxic materials while improving the device performance is a major challenge in the field of TFSCs. Herein, we report the fabrication of a-Si:H TFSCs with the n-type Si layer replaced with a self-assembled monolayer (3-aminopropyl) triethoxysilane (APTES). The X-ray photoelectron spectroscopy results showed that the amine groups from APTES attached with the hydroxyl groups (-OH) on the intrinsic Si (i-Si) surface to form a positive interfacial dipole towards i-Si. This interfacial dipole facilitated the decrease in electron extraction barrier by lowering the work function of the cathode. Consequently, the TFSC with APTES showed a higher fill factor (0.61) and power conversion efficiency (7.68%) than the reference device (without APTES). This performance enhancement of the TFSC with APTES can be attributed to its superior built-in potential and the reduction in the Schottky barrier of the cathode. In addition, the TFSCs with APTES showed lower leakage currents under dark conditions, and hence better charge separation and stability than the reference device. This indicates that APTES is a potential alternative to n-type Si layers, and hence can be used for the fabrication of non-toxic air-stable a-Si:H TFSCs with enhanced performance.

Effects of Embedded TiO2-x Nanoparticles on Triboelectric Nanogenerator Performance.

Triboelectric nanogenerators (TENGs) are used as self-power sources for various types of devices by converting external waves, wind, or other mechanical energies into electric power. However, obtaining a high-output performance is still of major concern for many applications. In this study, to enhance the output performance of polydimethylsiloxane (PDMS)-based TENGs, highly dielectric TiO2-x nanoparticles (NPs) were embedded as a function of weight ratio. TiO2-x NPs embedded in PDMS at 5% showed the highest output voltage and current. The improved output performance at 5% is strongly related to the change of oxygen vacancies on the PDMS surface, as well as the increased dielectric constant. Specifically, oxygen vacancies in the oxide nanoparticles are electrically positive charges, which is an important factor that can contribute to the exchange and trapping of electrons when driving a TENG. However, in TiO2-x NPs containing over 5%, the output performance was significantly degraded because of the increased leakage characteristics of the PDMS layer due to TiO2-x NPs aggregation, which formed an electron path.

Enhancement of the Device Performance and the Stability with a Homojunction-structured Tungsten Indium Zinc Oxide Thin Film Transistor.

Tungsten-indium-zinc-oxide thin-film transistors (WIZO-TFTs) were fabricated using a radio frequency (RF) co-sputtering system with two types of source/drain (S/D)-electrode material of conducting WIZO (homojunction structure) and the indium-tin oxide (ITO) (heterojunction structure) on the same WIZO active-channel layer. The electrical properties of the WIZO layers used in the S/D electrode and the active-channel layer were adjusted through oxygen partial pressure during the deposition process. To explain enhancements of the device performance and stability of the homojunction-structured WIZO-TFT, a systematic investigation of correlation between device performance and physical properties at the interface between the active layer and the S/D electrodes such as the contact resistance, surface/interfacial roughness, interfacial-trap density, and interfacial energy-level alignments was conducted. The homojunction-structured WIZO-TFT exhibited a lower contact resistance, smaller interfacial-trap density, and flatter interfacial roughness than the WIZO-TFT with the heterojunction structure. The 0.09 eV electron barrier of the homojunction-structured WIZO-TFT is lower than the 0.21 eV value that was obtained for the heterojunction-structured WIZO-TFT. This reduced electron barrier may be attributed to enhancements of device performance and stability, that are related to the carrier transport.

Characterization of Rotational Stacking Layers in Large-Area MoSe2 Film Grown by Molecular Beam Epitaxy and Interaction with Photon.

Transition metal dichalcogenides (TMDCs) are promising next-generation materials for optoelectronic devices because, at subnanometer thicknesses, they have a transparency, flexibility, and band gap in the near-infrared to visible light range. In this study, we examined continuous, large-area MoSe2 film, grown by molecular beam epitaxy on an amorphous SiO2/Si substrate, which facilitated direct device fabrication without exfoliation. Spectroscopic measurements were implemented to verify the formation of a homogeneous MoSe2 film by performing mapping on the micrometer scale and measurements at multiple positions. The crystalline structure of the film showed hexagonal (2H) rotationally stacked layers. The local strain at the grain boundaries was mapped using a geometric phase analysis, which showed a higher strain for a 30° twist angle compared to a 13° angle. Furthermore, the photon-matter interaction for the rotational stacking structures was investigated as a function of the number of layers using spectroscopic ellipsometry. The optical band gap for the grown MoSe2 was in the near-infrared range, 1.24-1.39 eV. As the film thickness increased, the band gap energy decreased. The atomically controlled thin MoSe2 showed promise for application to nanoelectronics, photodetectors, light emitting diodes, and valleytronics.

Unraveling the Issue of Ag Migration in Printable Source/Drain Electrodes Compatible with Versatile Solution-Processed Oxide Semiconductors for Printed Thin-Film Transistor Applications.

In recent decades, solution-processable, printable oxide thin-film transistors have garnered a tremendous amount of attention given their potential for use in low-cost, large-area electronics. However, printable metallic source/drain electrodes undergo undesirable electrical/thermal migration at an interfacial stack of the oxide semiconductor and metal electrode. In this study, we report oleic acid-capped Ag nanoparticles that effectively suppress the significant Ag migration and facilitate high field-effect mobilities in oxide transistors. The origin of the role of surface-capped Ag nanoparticles is clarified with comparative studies based on X-ray photoelectron spectroscopy and X-ray absorption spectroscopy.

Differences in end-of-life care decision making between patients with and without cancer.

BACKGROUND: Most patients and families do not want invasive life-sustaining procedures when recovery is unlikely. We compared the clinical features of advance directives (ADs) of patients with and without cancer. METHODS: The ADs were obtained from retrospectively reviewing electronic medical records of 699 consecutive patients who died from April 2011 to July 2012. RESULTS: Patients with cancer were more likely to have written ADs: 265 (85.8%) patients with cancer and 277 (71.0%) noncancer patients (P < .001). Significantly more noncancer patients were in the intensive care unit, indicating that they had received or were receiving invasive treatments. Noncancer patients requested life-sustaining treatment more frequently but symptom control less frequently than patients with cancer. CONCLUSION: Advance care planning in patients with incurable, noncancer disease is important to guarantee patient autonomy at the end of life.

A randomized phase II study to assess the effectiveness of fluid therapy or intensive nutritional support on survival in patients with advanced cancer who cannot be nourished via enteral route.

BACKGROUND: Experts advise against parenteral nutrition (PN) for patients with advanced cancer at the end of life. But because many patients and families fear starvation, many physicians administer PN to patients with terminal cancer in Korea. OBJECTIVE: We designed this study to investigate the effect of PN on survival in patients with terminal cancer at the end of life. DESIGN: We planned a randomized phase II study enrolling 116 patients randomized to receive either fluid or PN. SETTING/SUBJECTS: Eligible patients are who could not tolerate enteral feeding and had short life expectancies (<3 months) due to progressive cancer. Patients with functioning bowels were excluded. MEASUREMENTS: The primary end point was overall survival and the secondary end point was total administered calories. RESULTS: We prospectively enrolled 31 consecutive patients and 16 patients were assigned to the PN group. The study ended early because many patients and families were extremely concerned about starvation. The baseline characteristics, including nutritional parameters, were not significantly different between the two groups. The mean administered calories was 374.7 (± 71.7) kcal/d for the fluid group and 1286.8 (± 108.3) kcal/d for the PN group (p<0.001). Median survival was 8 days (95% confidence interval [CI], 5.7-10.3 days) in the fluid group and 13 days (95% CI: 3.1-22.9 days) in the PN group, and this difference was not statistically significant (p = 0.982 by Log-rank test). CONCLUSIONS: This study did not conclusively determine the role of PN for patients with advanced cancer, however, PN support failed to significantly prolong survival in these patients compared to similar patients receiving only fluid.

Intra-peritoneal interleukin-6 system is a potent determinant of the baseline peritoneal solute transport in incident peritoneal dialysis patients.

BACKGROUND: Interleukin-6 (IL-6) is a key player in modulating inflammation. IL-6 and soluble IL-6 receptor (sIL-6R) complex induces the synthesis and secretion of various chemokines, adhesion molecules and angiogenic molecules. We hypothesized that the baseline peritoneal solute transport rate (PSTR) early after commencing peritoneal dialysis (PD) may depend largely on the IL-6/sIL-6R system. We also hypothesized that the dialysate concentrations of IL-6/sIL-6R could be closely related to local inflammation or angiogenesis in the peritoneal cavity. METHODS: Fifty incident patients with a modified peritoneal equilibration test result within 3 months after commencing PD and without a previous history of peritonitis were enrolled. Clinical parameters such as age, sex, comorbid disease, body mass index, residual renal function and C-reactive protein were assessed. Serum and dialysate markers including CA125, IL-6, sIL-6R, monocyte chemoattractant protein-1 (MCP-1), vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2) were measured and correlated with PSTR. RESULTS: Dialysate concentrations of IL-6 (r = 0.576, P < 0.001), MCP-1 (r = 0.408, P = 0.003) and Ang-2 (r = 0.408, P = 0.003) correlated with mass transfer area coefficient for creatinine (MTAC(cr)), respectively. Dialysate appearance rate (AR) of albumin correlated with dialysate concentrations of CA125 (r = 0.751, P < 0.001), IL-6 (r = 0.303, P = 0.039), sIL-6R (r = 0.497, P < 0.001), MCP-1 (r = 0.488, P < 0.001), VEGF (r = 0.443, P = 0.004) and Ang-2 (r = 0.488, P < 0.001). Neither MTAC(cr) nor AR of albumin was associated with systemic markers. Multivariate analysis showed that MTAC(cr) is independently associated with dialysate IL-6 and serum albumin. It also showed that AR of albumin is independently predicted by dialysate sIL-6R. Dialysate IL-6 correlated with dialysate concentrations of CA125 MCP-1, VEGF and Ang-2. CONCLUSION: Our study from incident PD patients suggested that (i) dialysate the IL-6 system is a potent determinant of baseline PSTR and (ii) elevation of IL-6 in the dialysate is associated with up-regulation of intra-peritoneal inflammatory and angiogenic molecules.