Stability of Graphene and Influence of AlN Surface Pits on GaN Remote Heteroepitaxy for Exfoliation.

Remote epitaxy is a promising technology that has recently attracted considerable attention, which enables the growth of thin films that copy the crystallographic characteristics of the substrate through two-dimensional material interlayers. The grown films can be exfoliated to form freestanding membranes, although it is often challenging to apply this technique if the substrate materials are prone to damage under harsh epitaxy conditions. For example, remote epitaxy of GaN thin films on graphene/GaN templates has not been achieved by a standard metal-organic chemical vapor deposition (MOCVD) method due to such damages. Here, we report GaN remote heteroepitaxy on graphene/AlN templates by MOCVD and investigate the influence of surface pits in AlN on the growth and exfoliation of GaN thin films. We first show the thermal stability of graphene before GaN growth, based on which two-step growth of GaN on graphene/AlN is developed. The GaN samples are successfully exfoliated after the first step of the growth at 750 °C, whereas the exfoliation failed after the second step at 1050 °C. In-depth analysis confirms that the pits in AlN templates lead to the degradation of graphene near the area and thus the alteration of growth modes and the failure of exfoliation. These results exemplify the importance of chemical and topographic properties of growth templates for successful remote epitaxy. It is one of the key factors for III-nitride-based remote epitaxy, and these results are expected to be of great help in realizing complete remote epitaxy using only MOCVD.

Novel Mg- and Ga-doped ZnO/Li-Doped Graphene Oxide Transparent Electrode/Electron-Transporting Layer Combinations for High-Performance Thin-Film Solar Cells.

Herein, a novel combination of Mg- and Ga-co-doped ZnO (MGZO)/Li-doped graphene oxide (LGO) transparent electrode (TE)/electron-transporting layer (ETL) has been applied for the first time in Cu2 ZnSn(S,Se)4 (CZTSSe) thin-film solar cells (TFSCs). MGZO has a wide optical spectrum with high transmittance compared to that with conventional Al-doped ZnO (AZO), enabling additional photon harvesting, and has a low electrical resistance that increases electron collection rate. These excellent optoelectronic properties significantly improved the short-circuit current density and fill factor of the TFSCs. Additionally, the solution-processable alternative LGO ETL prevented plasma-induced damage to chemical bath deposited cadmium sulfide (CdS) buffer, thereby enabling the maintenance of high-quality junctions using a thin CdS buffer layer (≈30 nm). Interfacial engineering with LGO improved the Voc of the CZTSSe TFSCs from 466 to 502 mV. Furthermore, the tunable work function obtained through Li doping generated a more favorable band offset in CdS/LGO/MGZO interfaces, thereby, improving the electron collection. The MGZO/LGO TE/ETL combination achieved a power conversion efficiency of 10.67%, which is considerably higher than that of conventional AZO/intrinsic ZnO (8.33%).

The Role of the Graphene Oxide (GO) and Reduced Graphene Oxide (RGO) Intermediate Layer in CZTSSe Thin-Film Solar Cells.

Cu2ZnSn(S,Se)4 (CZTSSe) solar cells with low cost and eco-friendly characteristics are attractive as future sources of electricity generation, but low conversion efficiency remains an issue. To improve conversion efficiency, a method of inserting intermediate layers between the CZTSSe absorber film and the Mo back contact is used to suppress the formation of MoSe2 and decomposition of CZTSSe. Among the candidates for the intermediate layer, graphene oxide (GO) and reduced GO have excellent properties, including high-charge mobility and low processing cost. Depending on the type of GO, the solar cell parameters, such as fill factor (FF), were enhanced. Thus, the conversion efficiency of 6.3% was achieved using the chemically reduced GO intermediate layer with significantly improved FF.

Improving Ultraviolet Responses in Cu2ZnSn(S,Se)4 Thin-Film Solar Cells Using Quantum Dot-Based Luminescent Down-Shifting Layer.

Quantum dot (QD)-based luminescent down-shifting (LDS) layers were deposited on Cu2ZnSn(S,Se)4 (CZTSSe) solar cells via the drop-casting method. The LDS layers can easily widen the narrow absorption wavelength regions of single-junction solar cells and enable improvement of the short-circuit current. The optical properties of LDS layers deposited on glass and containing different QD contents were analyzed based on their transmittance, reflectance, and absorbance. The absorber films to be used in the CZTSSe solar cells were determined by X-ray diffraction measurements and Raman spectroscopy to determine their crystal structures and secondary phases, respectively. The completed CZTSSe solar cells with LDS layers showed increased ultraviolet responses of up to 25% because of wavelength conversion by the QDs. In addition, the impact of the capping layer, which was formed to protect the QDs from oxygen and moisture, on the solar cell performance was analyzed. Thus, a maximal conversion efficiency of 7.3% was achieved with the 1.0 mL QD condition; furthermore, to the best of our knowledge, this is the first time that LDS layers have been experimentally demonstrated for CZTSSe solar cells.

Complete response in hepatocellular carcinoma with lymph node metastasis by combination therapy of atezolizumab and bevacizumab: a case report

Sorafenib is the oldest first line systemic treatment in patients with advanced hepatocellularcarcinoma (HCC) and has been used exclusively for nearly 10 years. The superiority ofadministering a combination of atezolizumab plus bevacizumab (AteBeva) compared tosorafenib as first line systemic treatment for unresectable HCC was recently proven duringthe IMbrave150 Phase III randomized trial. While clinicians can expect improved responsesand treatment outcomes due to the good results of the IMbrave 150 trial, they must alsoconsider that atezolizumab can cause various immune-related adverse events (IrAEs). Basedon the above suggestions, we herein present a case of HCC with lymph node metastasiswho achieved complete remission following treatment with AteBeva and developed an IrAE(adrenal insufficiency). Further study of real-life data regarding combination therapy withAteBeva is needed to manage patients with advanced HCC.

Complete response in hepatocellular carcinoma with lymph node metastasis by combination therapy of atezolizumab and bevacizumab: a case report

Sorafenib is the oldest first line systemic treatment in patients with advanced hepatocellularcarcinoma (HCC) and has been used exclusively for nearly 10 years. The superiority ofadministering a combination of atezolizumab plus bevacizumab (AteBeva) compared tosorafenib as first line systemic treatment for unresectable HCC was recently proven duringthe IMbrave150 Phase III randomized trial. While clinicians can expect improved responsesand treatment outcomes due to the good results of the IMbrave 150 trial, they must alsoconsider that atezolizumab can cause various immune-related adverse events (IrAEs). Basedon the above suggestions, we herein present a case of HCC with lymph node metastasiswho achieved complete remission following treatment with AteBeva and developed an IrAE(adrenal insufficiency). Further study of real-life data regarding combination therapy withAteBeva is needed to manage patients with advanced HCC.

Impact of Na Doping on the Carrier Transport Path in Polycrystalline Flexible Cu2ZnSn(S,Se)4 Solar Cells.

It is well-known that the alkali doping of polycrystalline Cu2ZnSn(S,Se)4 (CZTSSe) and Cu(In,Ga)(Se,S)2 has a beneficial influence on the device performance and there are various hypotheses about the principles of performance improvement. This work clearly explains the effect of Na doping on the fill factor (FF) rather than on all of the solar cell parameters (open-circuit voltage, FF, and sometimes short circuit current) for overall performance improvement. When doping is optimized, the fabricated device shows sufficient built-in potential and selects a better carrier transport path by the high potential difference between the intragrains and the grain boundaries. On the other hand, when doping is excessive, the device shows low contact potential difference and FF and selects a worse carrier transport path even though the built-in potential becomes stronger. The fabricated CZTSSe solar cell on a flexible metal foil optimized with a 25 nm thick NaF doping layer achieves an FF of 62.63%, thereby clearly showing the enhancing effect of Na doping.

Enhanced Emission of Deep Ultraviolet Light-Emitting Diodes through Using Work Function Tunable Cu Nanowires as the Top Transparent Electrode.

Deep ultraviolet light-emitting diodes (DUV LEDs) (<280 nm) have been important light sources for broad applications in, e.g., sterilization, purification, and high-density storage. However, the lack of excellent transparent electrodes in the DUV region remains a challenging issue. Here, we demonstrate an architectural engineering scheme to flexibly tune the work function of Cu@shell nanowires (NWs) as top transparent electrodes in DUV LEDs. By fast encapsulation of shell metals on Cu NWs and a shift of electron binding energy, the electronic work function could be widely tailored down to 4.37 eV and up to 5.73 eV. It is revealed that the high work function of Cu@Ni and Cu@Pt NWs could overcome the interfacial barrier to p-AlGaN and achieve direct ohmic contact with high transparency (91%) in 200-400 nm. Completely transparent DUV LED chips are fabricated and successfully lighted with sharp top emission (wall-plug efficiency reaches 3%) under a turn-on voltage of 6.4 V. This architectural strategy is of importance in providing highly transparent ohmic electrodes for optoelectronic devices in broad wavelength regions.

Flexible High-Efficiency CZTSSe Solar Cells on Diverse Flexible Substrates via an Adhesive-Bonding Transfer Method.

Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells are showing great promise due to using earth-abundant and nontoxic materials and tuning the band gap through the amount of S and Se. Flexible high-efficiency CZTSSe solar cells are one of the outstanding research challenges because they currently require the use of thick glass substrates due to the high-temperature heat treatment process, and for this reason, few flexible CZTSSe solar cells have been reported. Furthermore, most researchers have used thin glass and metal substrates with little flexibility; the power conversion efficiency (PCE or η) values of the solar cells made with them have been slightly lower. To overcome these hurdles, we transferred high-efficiency CZTSSe solar cells formed on a soda-lime glass substrate to flexible substrates via an adhesive-bonding transfer method. Through this method, we were able to achieve the PCE of 5.8-7.1% on completely flexible substrates such as cloth, paper, and poly(ethylene terephthalate) (PET). In particular, we were able to produce a CZTSSe solar cell on a PET substrate with a PCE of 7.1%, which is the highest among fully flexible CZTSSe solar cells currently known to us. In addition, we deeply analyzed the PCE degradation of the flexible CZTSSe solar cell fabricated by the transfer method through a panoramic focused ion-beam image and nanoindentation. From the results of our work, we provide an insight into the possibility of making flexible high-efficiency CZTSSe solar cells using our transfer method.

Improved efficiency of InGaN/GaN light-emitting diodes with perpendicular magnetic field gradients.

The effect of magnetic fields on the optical output power of flip-chip light-emitting diodes (LEDs) with InGaN/GaN multiple quantum wells (MQWs) was investigated. Films and circular disks comprising ferromagnetic cobalt/platinum (Co/Pt) multilayers were deposited on a p-ohmic reflector to apply magnetic fields in the direction perpendicular to the MQWs of the LEDs. At an injection current of 20 mA, the ferromagnetic Co/Pt multilayer film increased the optical output power of the LED by 20% compared to an LED without a ferromagnetic Co/Pt multilayer. Furthermore, the optical output power of the LED with circular disks was 40% higher at 20 mA than the output of the LED with a film. The increase of the optical output power of the LEDs featuring ferromagnetic Co/Pt multilayers is attributed to the magnetic field gradient in the MQWs, which increases the carrier path in the MQWs. The time-resolved photoluminescence measurement indicates that the improvement of optical output power is owing to an enhanced radiative recombination rate of the carriers in the MQWs as a result of the magnetic field gradient from the ferromagnetic Co/Pt multilayer.

Spontaneous and Selective Nanowelding of Silver Nanowires by Electrochemical Ostwald Ripening and High Electrostatic Potential at the Junctions for High-Performance Stretchable Transparent Electrodes.

Metal nanowires have been gaining increasing attention as the most promising stretchable transparent electrodes for emerging field of stretchable optoelectronic devices. Nanowelding technology is a major challenge in the fabrication of metal nanowire networks because the optoelectronic performances of metal nanowire networks are mostly limited by the high junction resistance between nanowires. We demonstrate the spontaneous and selective welding of Ag nanowires (AgNWs) by Ag solders via an electrochemical Ostwald ripening process and high electrostatic potential at the junctions of AgNWs. The AgNWs were welded by depositing Ag nanoparticles (AgNPs) on the conducting substrate and then exposing them to water at room temperature. The AgNPs were spontaneously dissolved in water to form Ag+ ions, which were then reduced to single-crystal Ag solders selectively at the junctions of the AgNWs. Hence, the welded AgNWs showed higher optoelectronic and stretchable performance compared to that of as-formed AgNWs. These results indicate that electrochemical Ostwald ripening-based welding can be used as a promising method for high-performance metal nanowire electrodes in various next-generation devices such as stretchable solar cells, stretchable displays, organic light-emitting diodes, and skin sensors.

High-performance metal mesh/graphene hybrid films using prime-location and metal-doped graphene.

We introduce high-performance metal mesh/graphene hybrid transparent conductive layers (TCLs) using prime-location and metal-doped graphene in near-ultraviolet light-emitting diodes (NUV LEDs). Despite the transparency and sheet resistance values being similar for hybrid TCLs, there were huge differences in the NUV LEDs' electrical and optical properties depending on the location of the graphene layer. We achieved better physical stability and current spreading when the graphene layer was located beneath the metal mesh, in direct contact with the p-GaN layer. We further improved the contact properties by adding a very thin Au mesh between the thick Ag mesh and the graphene layer to produce a dual-layered metal mesh. The Au mesh effectively doped the graphene layer to create a p-type electrode. Using Raman spectra, work function variations, and the transfer length method (TLM), we verified the effect of doping the graphene layer after depositing a very thin metal layer on the graphene layers. From our results, we suggest that the nature of the contact is an important criterion for improving the electrical and optical performance of hybrid TCLs, and the method of doping graphene layers provides new opportunities for solving contact issues in other semiconductor devices.

Very thin ITO/metal mesh hybrid films for a high-performance transparent conductive layer in GaN-based light-emitting diodes.

In this paper, we introduce very thin Indium tin oxide (ITO) layers (5, 10, and 15 nm) hybridized with a metal mesh to produce high-performance transparent conductive layers (TCLs) in near-ultraviolet light-emitting diodes (NUV LEDs). Using UV-vis-IR spectrometry, Hall measurement, and atomic force microscopy, we found that 10 nm was the optimal thickness for the very thin ITO layers in terms of outstanding transmittance and sheet resistance values as well as stable contact properties when hybridized with the metal mesh. The proposed layers showed a value of 4.56 Ω/□ for sheet resistance and a value of 89.1% for transmittance. Moreover, the NUV LEDs fabricated with the hybrid TCLs achieved ∼140% enhanced light output power compared to that of 150 nm thick ITO layers. Finally, to verify the practical usage of the TCLs for industrial applications, we packaged the NUV LED chips and obtained improved turn-on voltage (3.48 V) and light output power (∼116%) performance.

Nine Cases of Sporadic Acute Hepatitis E in Korea / 대한간학회지

Hepatitis E virus is an enterically transmitted virus that causes endemic cases of acute hepatitis in many countries in Africa, and Southeast and Central Asia. Sporadic cases of acute hepatitis E also have been reported in developed countries. In non-endemic areas, most of the sporadic cases of hepatitis E are introduced from the endemic areas. Until now, only three cases of acute hepatitis E have been reported in Korea. Recently, we experienced nine cases of acute hepatitis, in which serologic studies showed positive of IgM anti-HEV. We report these as cases of acute hepatitis E. These cases suggest that HEV infection occurs sporadically in Korea and should be considered as a cause of cryptogenic acute hepatitis.

A Case of Multiple Myeloma Presenting as Non-obstructive Jaundice Due to Plasma Cell Infiltration of the Liver

Extraosseous manifestations are found in less than 5% of the patients with multiple myeloma. We reported here on a rare case of multiple myeloma presenting as non-obstructive jaundice due to diffuse plasma cell infiltration of the liver. A 70-year-old man was referred to our hospital because of general weakness, weight loss, jaundice, anemia and proteinuria. The laboratory studies showed: hemoglobin 8.5g/dL, calcium 10.3mg/dL, creatinine 1.3mg/dL, AST 41IU/L, ALT 26IU/L, alkaline phosphatase 304IU/L, total bilirubin 4.0mg/dL, direct bilirubin 2.3mg/dL and 24 hour urinary protein 1,120mg. The serologic tests for hepatitis B and C virus were negative. The abdominal CT scans were normal. The urinary protein studies revealed a M component of the lamda type light chain. The bone marrow biopsy showed atypical plasma cells, and the liver biopsy showed a diffuse sinusoidal infiltration of plasma cells.

Two different cases of episodic angioedema with eosinophilia / 대한내과학회지

Episodic angioedema with eosinophilia (Gleich's syndrome) is characterized by recurrent angioedema, fever, weight gain and peripneral eosinophilia. The symptoms and clinical course differ markedly from the idiopathic hypereosinophilic syndrome, including an absence of end organ involvement and a better prognosis. A transient variant, mainly reported in Japan, which is limited to a single attack, is usually less severe than the episodic type. Here we describe two young patients, one of those is the episodic type and the other is the transient type. We suggest that episodic angioedema with eosinophilia is not rare, and should be widely recognized as a new clinical entity for accurate and prompt diagnosis. Awareness and distinction from the hypereosinophilic syndrome is important because of the favorable prognosis and rapid response to corticosteroid therapy.