Silicon germanium photo-blocking layers for a-IGZO based industrial display

Amorphous indium- gallium-zinc oxide (a-IGZO) has been intensively studied for the application to active matrix flat-panel display because of its superior electrical and optical properties. However, the characteristics of a-IGZO were found to be very sensitive to external circumstance such as light illumination, which dramatically degrades the device performance and stability practically required for display applications. Here, we suggest the use for silicon-germanium (Si-Ge) films grown plasmaenhanced chemical vapour deposition (PECVD) as photo-blocking layers in the a-IGZO thin film transistors (TFTs). The charge mobility and threshold voltage (V-th) of the TFTs depend on the thickness of the Si-Ge films and dielectric buffer layers (SiNX), which were carefully optimized to be similar to 200 nm and similar to 300 nm, respectively. As a result, even after 1,000 s illumination time, the V-th and electron mobility of the TFTs remain unchanged, which was enabled by the photo-blocking effect of the Si-Ge layers for a-IGZO films. Considering the simple fabrication process by PECVD with outstanding scalability, we expect that this method can be widely applied to TFT devices that are sensitive to light illumination.

Augmented Mechanical Forces of the Surface-Modified Nanoporous Acupuncture Needles Elicit Enhanced Analgesic Effects

Over the past several decades, clinical studies have shown significant analgesic effects of acupuncture. The efficacy of acupuncture treatment has improved with the recent development of nanoporous needles (PN), which are produced by modifying the needle surface using nanotechnology. Herein, we showed that PN at acupoint ST36 produces prolonged analgesic effects in an inflammatory pain model; the analgesic effects of PN acupuncture were sustained over 2 h, while those using a conventional needle (CN) lasted only 30 min. In addition, the PN showed greater therapeutic effects than CN after 10 acupuncture treatments once per day for 10 days. We explored how the porous surface of the PN contributes to changes in local tissue, which may in turn result in enhanced analgesic effects. We showed that the PN has greater rotational torque and pulling force than the CN, particularly at acupoints ST36 and LI11, situated on thick muscle layers. Additionally, in ex vivo experiments, the PN showed greater winding of subcutaneous connective tissues and muscle layers. Our results suggest that local mechanical forces are augmented by the PN and its nanoporous surface, contributing to the enhanced and prolonged analgesic effects of PN acupuncture.1

Simple Approach to the Highly Efficient and Cost-Effective Inverted Perovskite Solar Cells via Solvent-Engineered Electron-Transporting Layers of Fullerene

With dramatic growth in the photovoltaic (PV) market, perovskite solar cells (PSCs) have achieved remarkable performance and demonstrated enormous potential for use in next-generation PVs. In particular, inverted PSCs have advantages in lowering manufacturing costs because they are suitable for low-temperature printable processability and compatibility with existing silicon PVs for tandem cells. However, for the successful commercialization of PSC-based modules, material cost, a crucial factor, has not been considered in depth. Most inverted PSCs with the highest performance usually consist of fullerene derivatives, which are expensive but difficult to replace with other materials. Therefore, a rational method is needed to solve this problem, and we propose a simple idea to reduce material costs. We systematically investigated the correlation between the properties of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) films and various solvents with different boiling points. We discovered that the highly volatile dichloromethane (DCM) solvent forms a thick and uniform PCBM layer even at quarter concentrations. The DCM–PCBM layer improves the interfacial properties of the PCBM–perovskite film, leading to a device with superior performance compared to that of a device prepared with the PCBM layers from the other solvents. Finally, we successfully demonstrated a high-efficiency inverted PSC based on DCM–PCBM with a maximum power conversion efficiency (PCE) of 22.4%

Large-scale transfer-free growth of thin graphite films at low temperature for solid diffusion barriers

Amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) have been under intense investigation as one of the promising candidates for active matrix flat-panel displays. However, solid diffusion of a-IGZO to other layers during TFT device fabrication highly degrades their electrical and optical properties. It is expected that the diffusion-impenetrable properties of graphitic materials can be utilized as diffusion barriers. A conventional transfer method and direct growth on TFTs with high temperature are limited due to wet transfer conditions and low T-g (similar to 540 degrees C) of the glass substrates, respectively. Here we report the large-scale transfer-free growth of thin graphite films at low temperature (similar to 350 degrees C) for solid diffusion barriers in the a-IGZO TFTs using plasma enhanced chemical vapor deposition (PECVD), which can be widely used to protect solid-diffusion for sustainable and scalable future industrial technology

Control of Crystallinity in PbPc:C₆₀ Blend Film and Application for Inverted Near-Infrared Organic Photodetector

Inverted near-infrared (NIR) organic photodetectors (OPDs) are required to combine the OPDs with an n-channel silicon-based integrated circuit. NIR absorption in the 930–960 nm range is important because the intensity of solar irradiation is low in this wavelength regime. Here, we controlled the crystallinity of lead­(II) phthalocyanine (PbPc) in a PbPc:C₆₀ blend film to obtain NIR absorption. To form a triclinic phase responsible for NIR light absorption, a substrate was heated during fabrication and C₆₀ was used as a templating layer, as well as an electron extraction layer, for an inverted structure. NIR absorption near 950 nm was enhanced, and the structural properties of the film changed dramatically. The OPD with enhanced NIR absorption exhibited a responsivity of 244 mA/W and an external quantum efficiency of 31.1% at a reverse bias of −3 V and 970 nm. The OPD detectivity also increased to 9.01 × 10¹² and 1.36 × 10¹¹ cm Hz^1/2/W under a zero bias and a reverse bias of −3 V, respectively

Efficient heat generation in large-area graphene films by electromagnetic wave absorption

Graphene has been intensively studied due to its outstanding electrical and thermal properties. Recently, it was found that the heat generation by Joule heating of graphene is limited by the conductivity of graphene. Here we suggest an alternative method to generate heat on a large-area graphene film more efficiently by utilizing the unique electromagnetic (EM) wave absorption property of graphene. The EM wave induces an oscillating magnetic moment generated by the orbital motion of moving electrons, which efficiently absorbs the EM energy and dissipate it as a thermal energy. In this case, the mobility of electron is more important than the conductivity, because the EMinduced diamagnetic moment is directly proportional to the speed of electron in an orbital motion. To control the charge carrier mobility of graphene we functionalized substrates with self-assembled monolayers (SAM). As the result, we find that the graphene showing the Dirac voltage close to zero can be more efficiently heated by EM waves. In addition, the temperature gradient also depends on the number of graphene. We expect that the efficient and fast heating of graphene films by EM waves can be utilized for smart heating windows and defogging windshields