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Mesenchymal stem cell (MSC)-derived small extracellular vesicles (MSC-sEVs) are known to exert immunosuppressive functions. This study showed that MSC-sEVs specifically convert T helper 17 (Th17) cells into IL-17 low-producer (ex-Th17) cells by degrading RAR-related orphan receptor γt (RORγt) at the protein level. In experimental autoimmune encephalomyelitis (EAE)-induced mice, treatment with MSC-sEVs was found to not only ameliorate clinical symptoms but also to reduce the number of Th17 cells in draining lymph nodes and the central nervous system. MSC-sEVs were found to destabilize RORγt by K63 deubiquitination and deacetylation, which was attributed to the EP300-interacting inhibitor of differentiation 3 (Eid3) contained in the MSC-sEVs. Small extracellular vesicles isolated from the Eid3 knockdown MSCs by Eid3-shRNA failed to downregulate RORγt. Moreover, forced expression of Eid3 by gene transfection was found to significantly decrease the protein level of RORγt in Th17 cells. Altogether, this study reveals the novel immunosuppressive mechanisms of MSC-sEVs, which suggests the feasibility of MSC-sEVs as an attractive therapeutic tool for curing Th17-mediated inflammatory diseases.

We present a study on the potential use of sulfuric acid-treated poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a viable alternative to indium tin oxide (ITO) electrodes in quantum dot light-emitting diodes (QLEDs). ITO, despite its high conductivity and transparency, is known for its disadvantages of being brittle, fragile, and expensive. Furthermore, due to the high hole injection barrier of quantum dots, the need for electrodes with a higher work function is becoming more significant. In this report, we present solution-processed, sulfuric acid-treated PEDOT:PSS electrodes for highly efficient QLEDs. The high work function of the PEDOT:PSS electrodes improved the performance of the QLEDs by facilitating hole injection. We demonstrated the recrystallization and conductivity enhancement of PEDOT:PSS upon sulfuric acid treatment using X-ray photoelectron spectroscopy and Hall measurement. Ultraviolet photoelectron spectroscopy (UPS) analysis of QLEDs showed that sulfuric acid-treated PEDOT:PSS exhibited a higher work function than ITO. The maximum current efficiency and external quantum efficiency based on the PEDOT:PSS electrode QLEDs were measured as 46.53 cd/A and 11.01%, which were three times greater than ITO electrode QLEDs. These findings suggest that PEDOT:PSS can serve as a promising replacement for ITO electrodes in the development of ITO-free QLED devices.

Low-temperature processing is important for improving the stability and performance of flexible quantum dot light-emitting diodes (QLEDs). In this study, QLEDs were fabricated using poly[bis(4-phenyl) (2,4,6-trimethylphenyl)amine] (PTAA) as a suitable hole transport layer (HTL) material owing to its low-temperature processability and vanadium oxide as the low-temperature solution-processable hole injection layer material. The maximum luminance and highest current efficiency of the QLEDs on a glass substrate with an optimal PTAA HTL was 8.9 × 104 Cd/m2 and 15.9 Cd/A, respectively, which was comparable to that of conventional devices. The QLEDs on a flexible substrate showed a maximum luminance of 5.4 × 104 Cd/m2 and highest current efficiency of 5.1 Cd/A. X-ray and ultraviolet photoelectron spectroscopies were used to investigate the chemical state and interfacial electronic structure according to the materials and the state changes of the HTL, respectively. The interfacial electronic structure showed that PTAA exhibited a better hole transport ability owing to its low hole injection barrier ($${\Phi }_{{\text{h}}}$$ Φ h ). Moreover, QLEDs with a PTAA HTL could operate as photosensors under reverse bias conditions. These results indicate that the low-temperature-processed PTAA HTL is suitable for improving the performance of flexible QLEDs.

Al-doped TiO2 (ATO) interfacial layer improves the charge balance and the performance of quantum-dot light-emitting diodes (QLEDs).

Vanadium oxide (V2O5) doped with Li (5, 10, and 15 mol%) was synthesized using an easy and low-cost solution process method and was used as a hole-injection layer (HIL) for quantum-dot light-emitting diodes (QLEDs).

A visible-light phototransistor have been fabricated by adding a solution-processed thin Al2O3 layer under the ZnO layer to improve the visible-light photodetection.

One of the major obstacles in the way of high-performance quantum dot light-emitting diodes (QLEDs) is the charge imbalance arising from more efficient electron injection into the emission layer than the hole injection. In previous studies, a balanced charge injection was often achieved by lowering the electron injection efficiency; however, high performance next-generation QLEDs require the hole injection efficiency to be enhanced to the level of electron injection efficiency. Here, we introduce a solution-processed HfO

We carried out KF postdeposition treatment (PDT) on a Cu(In,Ga)Se2 (CIGS) layer with a process time varying from 50 to 200 s. The highest CIGS solar-cell efficiency was achieved at a KF PDT process time of 50 s; in this condition, we observed the highest level of K element at the near-surface of the CIGS layer and the perfectly passivated pinholes on the CIGS surface. At process times above 150 s, the oversupplied KF agglomerated into large islands and was subsequently eliminated during the deposition of the chemical bath deposition (CBD)-Zn(O,S) buffer layer owing to the islands' water-soluble characteristics. As a result, the growth mechanism of the CBD-Zn(O,S) layer varied as a function of KF PDT process time. X-ray photoemission spectroscopy (XPS) measurements were used to examine the dependency of the chemical state on the KF PDT process time, and from the results, we formulated a chemical reaction model based on the shift in the elemental binding energy following deposition of the CBD-Zn(O,S) buffer layer. The chemical states of the K-In-Se phase, which have a beneficial effect on the solar-cell performance owing to the formation of durable and improved p-n junctions, are formed only at a KF PDT process time of 50 s. We derived band alignments from the XPS depth profiles by extracting the conduction- and valence-band offsets, and we used optical-pump-THz-probe spectroscopy to measure the ultrafast photocarrier lifetimes related to the defect states following KF PDT. Our key findings can be summarized as follows: (i) photocarrier transport is beneficial at a low barrier height, and (ii) the photocarrier lifetime increases when the K-In-Se phases are formed on the CIGS surface, which allows K+ ions to be effectively substituted into Cu vacancies.

A ZnMgO and ZnO double-layered structure was prepared to create a stepwise interfacial electronic structure to improve the electron-injection and electron-transport behaviors in quantum-dot light-emitting diodes (QLEDs). The current density of the electron-only device (EOD) with ZnMgO/ZnO was higher than that of the EOD with only ZnMgO. The detailed QLED interfacial electronic structure was measured using X-ray and ultraviolet photoelectron spectroscopy. A stepwise interfacial electronic structure for electron injection and electron transport was observed connecting the aluminum cathode to the ZnMgO conduction band minimum (CBM) via the ZnO CBM. The QLEDs with the ZnMgO/ZnO double electron transport layer showed an improved performance, with a maximum luminance and current efficiency of 90,892 cd m−2 and 19.2 cd A−1, respectively. Moreover, the turn-on voltage of the device was significantly reduced to 2.6 V due to the stepwise interfacial electronic structure between the aluminum cathode and ZnMgO CBM. This research provides a useful method for developing highly efficient and low turn-on voltage QLEDs using a ZnMgO/ZnO double ETL for next-generation display.

Visible-light phototransistors have been fabricated based on the heterojunction of zinc oxide (ZnO) and titanium oxide (TiO2). A thin layer of TiO2 was deposited onto the spin-coated ZnO film via atomic layer deposition (ALD). The electrical characteristics of the TiO2 layer were optimized by controlling the purge time of titanium isopropoxide (TTIP). The optimized TiO2 layer could absorb the visible-light from the sub-gap states near the conduction band of TiO2, which was confirmed via photoelectron spectroscopy measurements. Therefore, the heterostructure of TiO2/ZnO can absorb and generate photocurrent under visible light illumination. The oxygen-related-states were investigated via X-ray photoelectron spectroscopy (XPS), and the interfacial band structure between TiO2 and ZnO was evaluated via ultraviolet photoelectron spectroscopy (UPS). Oxygen-related states and subgap-states were observed, which could be used to generate photocurrent by absorbing visible light, even with TiO2 and ZnO having a wide bandgap. The optimized TiO2/ZnO visible-light phototransistor showed a photoresponsivity of 99.3 A W−1 and photosensitivity of 1.5 × 105 under the illumination of 520 nm wavelength light. This study provides a useful way to fabricate a visible-light phototransistor based on the heterostructure of wide bandgap oxide semiconductors.

The wide band gap of oxide semiconductors enables them to generate photocurrents through irradiation with high-energy photons, such as by ultraviolet light. To enhance the photoresponsivity of an oxide semiconductor to visible light, we fabricate a phototransistor by doping ZnO with Li. The amount of oxygen vacancies in ZnO is controlled by changing the concentration of lithium hydroxide in ZnO solution. Li dopants increase the electron concentration in ZnO, thereby improving the electrical behavior of ZnO thin-film transistors (TFTs). The Li-doped ZnO TFTs exhibit a high field-effect mobility of 10.15 cm2 V−1 s−1 and a high on/off ratio of ∼107. These oxygen vacancy states are located above the valence band of ZnO; therefore, they can generate a photocurrent upon irradiation of Li-doped ZnO TFTs with visible light. Li-Doped ZnO phototransistors exhibit excellent photodetection characteristics (photoresponsivity: 23.11 A W−1; photosensitivity: 4.94 × 106) upon 520 nm laser irradiation on the device, when the concentration of lithium hydroxide is 5 mol%. In addition, Li doped ZnO TFTs can be operated stably without light-induced aging effects or degradation caused by negative bias stress. Ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy measurements are performed to investigate the origin of the improved visible-light photoresponsivity of the Li-doped ZnO phototransistors. Our experimental results suggest that a visible-light photodetector can be developed using wide band gap ZnO.

Poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) is a commonly used material for the hole injection layer (HIL) in quantum-dot light-emitting diodes (QLEDs). In this work, we improved the performance of the QLED by using an organic–inorganic hybrid HIL. The hybrid HIL was prepared by mixing PEDOT:PSS with vanadium oxide (V2O5), which is a transition-metal oxide (TMO). The hole injection properties of PEDOT:PSS were improved according to the amount of V2O5 mixed into the PEDOT:PSS. The maximum luminance and current efficiency were 36 198 cd m−2 and 13.9 cd A−1, respectively, when the ratio of PEDOT:PSS and V2O5 was 10 : 1. Moreover, the operating lifetime exceeded 300 h, which is 10 times longer than the lifetime of the device with only PEDOT:PSS HIL. The improvement was analyzed using ultraviolet and X-ray photoelectron spectroscopy. We found that the density of state (DOS) of PEDOT:PSS near the Fermi energy level was increased by mixing V2O5. Therefore, the increase of DOS improved the hole injection and the performance of QLEDs. The result shows that the hybrid HIL can improve the performance and the stability of QLEDs.

We have developed a visible-light phototransistor with excellent photodetection characteristics and stability via atomic layer deposition (ALD) to add a thin layer of aluminum oxide (Al2O3) to quantum dot (QD)/zinc oxide (ZnO) films. Al2O3 was used to passivate the surface of the QDs and fill the interspace of the QDs. This led to a reduction in the number of QD surface traps and prevented damage due to the migration of aggressive metal atoms during electrode deposition. Additionally, some parts of Al2O3 deposited on the surface of ZnO triggered a doping effect by interacting with ZnO. This enhanced the electrical properties of ZnO TFTs by providing an extra electron and allowed the efficient transfer of photoelectrons from the QDs to ZnO by reducing the conduction band minimum of ZnO. Therefore, upon 520 nm laser irradiation Al2O3/QD/ZnO TFTs exhibited excellent photodetection characteristics (e.g., photosensitivity: 3.8 × 107, photoresponsivity: 46.8 A W−1, and photodetectivity: 4.5 × 1014 Jones) at a gate voltage of −5 V. Excellent electrical properties, such as saturation mobility of 1.72 cm V−1 s−1 and on/off current ratio of 1.8 × 106, were also realized. Furthermore, the photo-excited charge transfer mechanism was investigated using X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and time-resolved photoluminescence. Our experimental results suggest a method for realizing enhanced optoelectronic characteristics and stability of QD/ZnO TFTs via ALD-Al2O3 deposition, which is useful for developing high-performance visible phototransistors.

Mouse mesenchymal stem cells (MSCs) have been shown to suppress T cells. Especially, MSC-cultured media have shown suppressive functions against various immune cells including the T cells. However, the underlying immunosuppressive mechanisms of the MSC-cultured medium are not yet fully understood. In this study, we confirmed the T cell-suppression capacity of MSC culture supernatant (MSC-CS) through both apoptosis and cell cycle arrest, and hypothesized that the exosomes were the major immunosuppressive agents in the MSC-CS. MSC-derived exosomes (MSC-exo) exhibited potent suppressive effects on T cell proliferation while the rest of the supernatant fraction did not. Interestingly, the exosomes derived from MSC only induced the cell cycle arrest, and it was through the upregulation of p27kip1 protein and downregulation of Cdk2 protein. In conclusion, the exosomes secreted from MSCs could suppress the activated T cell proliferation through the induction of cell cycle arrest.

Zinc oxide (ZnO) is a commonly used electron transport layer in quantum-dot light-emitting diodes (QLEDs). In this study, we used a highly conductive ZnO film via a low-temperature process to improve the electron transport behavior of the QLEDs. The electron transport behavior of ZnO film was investigated from the electron only device, and the origin of high conductivity was figured out using x-ray photoelectron spectroscopy. We found that the oxygen vacancy, which can improve the carrier transport in ZnO film, was increased according to reduce the process temperature of ZnO. Meanwhile, the hydroxyl group, which contribute to the quenching effect, was decreased according to reduce the process temperature of ZnO. Therefore, high-performance QLEDs were fabricated using the low-temperature processed ZnO, and it showed an improved luminance and current efficiency in a full current range. The maximum luminance and current efficiency of the devices were measured as 65,391 Cd/m2 and 2.48 Cd/A, respectively. Moreover, the lifetime of the device was improved due to the low-temperature process. Therefore, we suggest that a highly conductive ZnO film could be formed through a low-temperature process, and it can improve the performance of QLEDs.

Conventional visible-light phototransistors based on the heterostructure of wide band gap zinc oxide (ZnO) and colloidal quantum dots (CdSe/ZnS QDs) have been studied. However, it is found that there are various deteriorated characteristics for their photoelectric behavior. Here, the phototransistors of an additional thin layer of TiO2 deposited onto the ZnO/QDs film using atomic layer deposition are developed for improving the performance of phototransistors. Small band gap QDs can absorb low-energy visible light and generate photoexcited charge carriers, which can be injected into the conduction band of wide band gap ZnO. Subsequently, the photoexcited charge carriers can be injected into the conduction band of TiO2 owing to the low injection barrier. Therefore, the ZnO/QDs phototransistor with the TiO2 layer can generate a larger photocurrent from visible light compared to a device without the TiO2 top layer. Moreover, the inorganic TiO2 layer improved the stability of the device. Under illumination with light at a wavelength of 520 nm, the maximum photosensitivity of the device was 4.2 × 106 and the transition rate was 0.728 ns−1, which is high enough to reduce the persistent photocurrent effect. This work offers a useful method to enhance the performance of visible-light phototransistors based on a heterostructure of oxide semiconductors and QDs.

Charge imbalance in quantum-dot light-emitting diodes (QLEDs) causes emission degradation. Therefore, many studies focused on improving hole injection into the QLEDs-emitting layer owing to lower hole conductivity compared to electron conductivity. Herein, CuCo2O4 has a relatively higher hole conductivity than other binary oxides and can induce an improved charge balance. As the annealing temperature decreases, the valence band maximum (VBM) of CuCo2O4 shifts away from the Fermi energy level (EF), resulting in an enhanced hole injection through better energy level alignment with hole transport layer. The maximum luminance and current efficiency of the CuCo2O4 hole injection layer (HIL) of the QLED were measured as 93,607 cd/m2 and 11.14 cd/A, respectively, resulting in a 656% improvement in luminous performance of QLEDs compared to conventional metal oxide HIL-based QLEDs. These results demonstrate that the electrical properties of CuCo2O4 can be improved by adjusting the annealing temperature, suggesting that solution-processed spinel can be applied in various optoelectronic devices.

High-luminance, efficient quantum-dot light-emitting diodes (QLEDs) have been achieved by optimizing the balance between the hole injection layer (HIL) and the hole transport layer (HTL). Different concentrations of vanadium oxide (V2O5) and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(4-sec-butylphenyl)diphenylamine)] (TFB) solutions were used to form the efficient HIL and HTL, respectively, for the QLEDs. The hole injection and transport behavior was characterized by using hole-only devices (HODs). The QLEDs, which were prepared with 0.5 wt.% of V2O5 and 0.1 wt.% of TFB as HIL and HTL, respectively, showed a maximum current efficiency of 2.27 cd·A−1 and a maximum luminance of 71,260 cd·m−2. Moreover, the turn-on voltage of the device was as low as 2.2 V due to the efficient carrier injection and transport. The results provide useful information for fabricating high-performance QLEDs.

One of the major obstacles in the way of high−performance quantum dot light−emitting diodes (QLEDs) is the charge imbalance arising from more efficient electron injection into the emission layer than the hole injection. In previous studies, a balanced charge injection was often achieved by lowering the electron injection efficiency; however, high performance next−generation QLEDs require the hole injection efficiency to be enhanced to the level of electron injection efficiency. Here, we introduce a solution−processed HfOx layer for the enhanced hole injection efficiency. A large amount of oxygen vacancies in the HfOx films creates gap states that lower the hole injection barrier between the anode and the emission layer, resulting in enhanced light−emitting characteristics. The insertion of the HfOx layer increased the luminance of the device to 166,600 cd/m2, and the current efficiency and external quantum efficiency to 16.6 cd/A and 3.68%, respectively, compared with the values of 63,673 cd/m2, 7.37 cd/A, and 1.64% for the device without HfOx layer. The enhanced light−emitting characteristics of the device were elucidated by X−ray photoelectron, ultra−violet photoelectron, and UV−visible spectroscopy. Our results suggest that the insertion of the HfOx layer is a useful method for improving the light−emitting properties of QLEDs.

The C-terminal fragment of CABIN1 interacts with calcineurin and represses the transcriptional activity of the nuclear factor of activated T cells (NFAT). However, the specific sequences and mechanisms through which it binds to calcineurin are unclear. This study determined that decameric peptide (CABIN1 residues 2146–2155) is minimally required for binding to calcineurin. This peptide contains a unique “PPTP” C-terminal sequence and a “PxIxIT” N-terminal motif. Furthermore, p38MAPK phosphorylated the threonine residue of the “PPTP” sequence under physiological conditions, dramatically enhancing the peptide’s binding affinity to calcineurin. Therefore, the CABIN1 peptide inhibited the calcineurin-NFAT pathway and the activation of T cells more efficiently than the VIVIT peptide without affecting calcineurin’s phosphatase activity. The CABIN1 peptide could thus be a more potent calcineurin inhibitor and provide therapeutic opportunities for various diseases caused by the calcineurin-NFAT pathway.

We carried out KF postdeposition treatment (PDT) on a Cu(In,Ga)Se

Islet transplantation is efficacious to prevent severe hypoglycemia and glycemic liability of selected patients of type 1 diabetes. However, since calcineurin inhibitor (CNI) causes β-cell and nephrotoxicity, alternative drug(s) with similar potency and safety profile to CNI will be highly desirable. Here we tested whether JAK3 inhibitor, tofacitinib could be used instead of tacrolimus in CIT07 immunosuppression regimen in cynomolgus nonhuman primate (NHP) model. Five independent streptozotocin (STZ)-induced diabetic monkeys were transplanted with MHC-mismatched allogeneic islets and three animals were further re-transplanted upon insufficient glycemic control or early islet graft rejection. After islet transplantation, blood glucose levels were quickly stabilized and maximal islet graft survival as measured by serum C-peptide concentration was >330, 98, >134, 31, or 22 days, respectively, after transplantation (median survival day; 98 days). Cellular and humoral immune responses were efficiently suppressed by JAK3 inhibitor-based immunosuppression during the follow-up periods. Although intermittent increases of the genome copy number of cynomolgus cytomegalovirus (CMV) were detected by quantitative real-time PCR analyses, serious infections or posttransplant lymphoproliferative disease (PTLD) was not found in all animals. Taken together, we have shown that JAK3 inhibitor could be used in replacement of tacrolimus in a highly translatable NHP islet transplantation model and these results suggest that JAK3 inhibitor will be potentially incorporated in human allogeneic islet transplantation.

Red, green, blue (RGB) selective zinc oxide (ZnO) phototransistors with multi-photoactive quantum-dot (QD) channels have been fabricated by a charge-assisted layer-by-layer (LbL) patterning process. QDs were patterned as RGB pixels in multi-photoactive QD channels through the LbL process. The solution-processed ZnO film, which acts as an active-channel layer of the ZnO TFTs, is patterned via a photoinduced surface engineering method to reduce the leakage current of the ZnO TFTs. The average off-current of the patterned ZnO TFTs reduced from 10−10 to 10−11 A. QDs absorb visible light and generate photoelectrons, which are then transferred to the ZnO to produce photocurrents. The device shows photoresponsivity of 9.4 mA/W, 12.5, and 137 A/W to the illumination of 638, 520, and 405 nm wavelength light. Our results suggest a promising way to develop an RGB selective phototransistor that uses QDs as a visible light absorption layer and ZnO as an active channel semiconductor.

A low-temperature solution-processable inorganic vanadium oxide (V2O5) hole injection layer (HIL) was synthesized for flexible quantum-dot light-emitting diodes (QLEDs). Efficient hole injection characteristics were observed in the hole-only devices; furthermore, the process temperature of V2O5 was as low as 30 °C. We investigated the source of the efficient hole injection behavior using ultraviolet and x-ray photoelectron spectroscopy. The density of gap states was found to increase in accordance with process temperature reduction. Therefore, QLEDs with low-temperature solution-processable V2O5 HILs were fabricated on a glass substrate, which showed excellent characteristics. The maximum luminance and luminous efficiency of the device were 56,717 Cd/m2 and 4.03 Cd/A, respectively. Due to the low-temperature process of the V2O5 HIL, it was also possible to fabricate QLEDs on a flexible plastic substrate without mechanical or thermal deformation of the substrate. Our results suggest that the low-temperature V2O5 inorganic HIL is a feasible alternative to organic HILs for flexible QLEDs.

The interfacial electronic structure between a W-doped In2O3 (IWO) transparent electrode and a V2O5 hole injection layer (HIL) has been investigated using ultraviolet photoelectron spectroscopy for high-performance and inorganic quantum-dot light-emitting diodes (QLEDs). Based on the interfacial electronic structure measurements, we found gap states in a V2O5 HIL at 1.0 eV below the Fermi level. Holes can be efficiently injected from the IWO electrode into poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(4-sec-butylphenyl)diphenylamine)] (TFB) through the gap states of V2O5, which was confirmed by the hole injection characteristics of a hole-only device. Therefore, conventional normal-structured QLEDs were fabricated on a glass substrate with the IWO transparent electrode and V2O5 HIL. The maximum luminance of the device was measured as 9443.5 cd m−2. Our result suggests that the IWO electrode and V2O5 HIL are a good combination for developing high-performance and inorganic QLEDs.

The photocurrent characteristics of zinc-oxide (ZnO) thin-film transistors (TFTs) prepared using radio-frequency sputtering and spin-coating methods were investigated. Various characterization methods were used to compare the physical and the chemical properties of the sputtered and the spin-coated ZnO films. X-ray photoelectron spectroscopy was used to investigate the chemical composition and state of the ZnO films. The transmittance and the optical band gap were measured by using UV-vis spectrometry. The crystal structures of the prepared ZnO films were examined by using an X-ray diffractometer, and the surfaces of the films were investigated by using scanning electron microscopy. ZnO TFTs were prepared using both sputter and solution processes, both of which showed photocurrent characteristics when illuminated by light. The sputtered ZnO TFTs had a photoresponsivity of 3.08 mA/W under illumination with 405-nm light while the solution-processed ZnO TFTs had a photoresponsivity of 5.56 mA/W. This study provides useful information for the development of optoelectronics based on ZnO.

Visible-light phototransistors have been fabricated based on the heterojunction of zinc oxide (ZnO) and titanium oxide (TiO

Dual-functional quantum-dots light emitting diodes (QLEDs) have been fabricated using solution processable vanadium oxide (V2O5) hole injection layer to control the carrier transport behavior. The device shows selectable functionalities of photo-detecting and light-emitting behaviors according to the different operating voltage conditions. The device emitted a bright green light at the wavelength of 536 nm, and with the maximum luminance of 31,668 cd/m2 in a forward bias of 8.6 V. Meanwhile, the device could operate as a photodetector in a reverse bias condition. The device was perfectly turned off in a reverse bias, while an increase of photocurrent was observed during the illumination of 520 nm wavelength light on the device. The interfacial electronic structure of the device prepared with different concentration V2O5 solution was measured in detail using x-ray and ultraviolet photoelectron spectroscopy. Both the highest occupied molecular orbital and the gap state levels were moved closer to the Fermi level, according to increase the concentration of V2O5 solution. The change of gap state position enables to fabricate a dual-functional QLEDs. Therefore, the device could operate both as a photodetector and as a light-emitting diode with different applied bias. The result suggests that QLEDs can be used as a photosensor and as a light-emitting diode for the future display industry.

Poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) is a commonly used material for the hole injection layer (HIL) in quantum-dot light-emitting diodes (QLEDs). In this work, we improved the performance of the QLED by using an organic-inorganic hybrid HIL. The hybrid HIL was prepared by mixing PEDOT:PSS with vanadium oxide (V

Porcine islet xenotransplantation is a promising alternative to overcome the shortage of organ donors. For the successful application of islet xenotransplantation, robust immune/inflammatory responses against porcine islets should be thoroughly controlled. Over the last few decades, there have been numerous attempts to surmount xenogeneic immune barriers. In this review, we summarize the current progress in immunomodulatory therapy for the clinical application of porcine islet xenotransplantation. Long-term graft survival of porcine islets was achieved by using anti-CD154 Ab-based regimens in a preclinical non-human primate (NHP) model. However, owing to a serious complication of thromboembolism in clinical trials, the development of an anti-CD154 Ab-sparing immunosuppressant procedure is required. The efficacy of new immunosuppressive practices that employ anti-CD40 Abs or other immunosuppressive reagents has been tested in a NHP model to realize their utility in porcine islet xenotransplantation. The recent progress in the development of immunomodulatory approaches, including the immunosuppressive regimen, which enables long-term graft survival in a pig-to-non-human primate islet xenotransplantation model, with their potential clinical applicability was reviewed.

Highly transparent optical logic circuits operated with visible light signals are fabricated using phototransistors with a heterostructure comprised of an oxide semiconductor (ZnO) with a wide bandgap and quantum dots (CdSe/ZnS QDs) with a small bandgap. ZnO serves as a highly transparent active channel, while the QDs absorb visible light and generate photoexcited charge carriers. The induced charge carriers can then be injected into the ZnO conduction band from the QD conduction band, which enables current to flow to activate the phototransistor. The photoexcited charge transfer mechanism is investigated using time-resolved photoluminescence spectroscopy, scanning Kelvin probe microscopy, and ultraviolet photoelectron spectroscopy. Measurements show that carriers in the QD conduction band can transfer to the ZnO conduction band under visible light illumination due to a change in the Fermi energy level. Moreover, the barrier for electron injection into the ZnO conduction band from the QD conduction band is low enough to allow photocurrent generation in the QDs/ZnO phototransistor. Highly transparent NOT, NOR, and NAND optical logic circuits are fabricated using the QDs/ZnO heterostructure and transparent indium tin oxide electrodes. This work provides a means of developing highly transparent optical logic circuits that can operate under illumination with low-energy photons such as those found in visible light.

Clinical islet transplantation has recently been a promising treatment option for intractable type 1 diabetes patients. Although early graft loss has been well studied and controlled, the mechanisms of late graft loss largely remains obscure. Since long-term islet graft survival had not been achieved in islet xenotransplantation, it has been impossible to explore the mechanism of late islet graft loss. Fortunately, recent advances where consistent long-term survival (≥6 months) of adult porcine islet grafts was achieved in five independent, diabetic nonhuman primates (NHPs) enabled us to investigate on the late graft loss. Regardless of the conventional immune monitoring methods applied in the post-transplant period, the initiation of late graft loss could rarely be detected before the overt graft loss observed via uncontrolled blood glucose level. Thus, we retrospectively analyzed the gene expression profiles in 2 rhesus monkey recipients using peripheral blood RNA-sequencing (RNA-seq) data to find out the potential cause(s) of late graft loss. Bioinformatic analyses showed that highly relevant immunological pathways were activated in the animal which experienced late graft failure. Further connectivity analyses revealed that the activation of T cell signaling pathways was the most prominent, suggesting that T cell-mediated graft rejection could be the cause of the late-phase islet loss. Indeed, the porcine islets in the biopsied monkey liver samples were heavily infiltrated with CD3+ T cells. Furthermore, hypothesis test using a computational experiment reinforced our conclusion. Taken together, we suggest that bioinformatics analyses with peripheral blood RNA-seq could unveil the cause of insidious late islet graft loss.

We fabricated W-doped In2O3 (IWO) films at room temperature on a flexible PET substrate using an in-line arc plasma ion plating system for application as flexible transparent conducting electrodes (FTCEs) in flexible organic light emitting diodes (OLEDs) and quantum dots light emitting diodes (QDLEDs). Due to the high-energy flux of the sublimated ions generated from the plasma region, the IWO films showed a well-developed crystalline structure with a low sheet resistance of 36.39 Ohm/square and an optical transmittance of 94.6% even though they were prepared at room temperature. The low sheet resistance of the IWO film processed at room temperature is attributed to the high mobility (59 cm2/V-s) in the well-developed crystalline structure of the ion-plated IWO film and screening effect of W dopants. In addition, the better adhesion of the ion-plated IWO film on the PET substrate led to small critical outer and inner bending radii of 6 and 3 mm, respectively, against substrate bending. Due to the low sheet resistance, high optical transmittance, better crystallinity, better adhesion, and outstanding flexibility of the ion-plated IWO films, the flexible OLEDs and QDLEDs with the IWO electrodes showed better performances than flexible OLEDs and QDLEDs with sputtered flexible ITO anodes. This indicates that in-line arc plasma ion plating is a promising large area coating technique to realize room temperature processed high-quality FTCEs for flexible OLEDs and QDLEDs.

Pancreatic islet transplantation is an ultimate solution for treating patients with type 1 diabetes (T1D). The pig is an ideal donor of islets for replacing scarce human islets. Besides immunological hurdles, non-immunological hurdles including fragmentation and delayed engraftment of porcine islets need solutions to succeed in porcine islet xenotransplantation. In this study, we suggest a simple but effective modality, a cell/islet co-localizing composite, to overcome these challenges. Endothelial-like mesenchymal stem cells (EMSCs), differentiated from bone-marrow derived mouse mesenchymal stem cells (MSCs), and MSCs evenly coated the surface of porcine islets (>85%) through optimized culture conditions. Both MSCs and EMSCs significantly reduced the fragmentation of porcine islets and increased the islet masses, designated as islet equivalents (IEQs). In fibrin in vitro and in vivo angiogenesis analysis, constructed EMSC-islet composites showed higher angiogenic potentials than naked islets, MSC-islet composites, or human endothelial cell-islet composites. This novel delivery method of porcine islets may have beneficial effects on the engraftment of transplanted islets by prevention of fragmentation and enhancement of revascularization.

The short-wavelength optical loss in the Cu(In,Ga)Se2 (CIGS) thin-film solar cells is inevitable owing to the substantial light absorption in the front layers such as the buffer layer and transparent conducting oxide (TCO) layer. Quantum dots (QDs) with CdSe/ZnS core–shell structure is utilized to increase the short-wavelength spectral response of the CIGS thin-film solar cells. The QDs absorbs photons in the short-wavelength region (μm-thick QD layer exhibited the highest increase of 1.86 mA cm−2 and 0.75% in the short-circuit current density and efficiency, respectively.

Solution-processable vanadium oxide (V 2 O 5 ) was used as an inorganic hole injection layer (HIL) to improve the performance and stability of quantum-dot light-emitting diodes (QLEDs). Non-acidic and non-hygroscopic V 2 O 5 solution was synthesized and spin-coated onto indium-tin-oxide (ITO)/glass substrate to serve as an HIL for QLEDs. QLEDs with a V 2 O 5 HIL showed efficient hole injection and had improved luminous efficiency and life-time. Maximum luminance and luminous efficiency of QLEDs fabricated under ambient conditions were 12,603 cd/m 2 and 2.96 Cd/A, respectively. Photoelectron spectroscopy measurements were conducted to construct an energy level diagram of the QLEDs, and we found that the gap states of V 2 O 5 enabled efficient hole-injection from ITO into the devices through the V 2 O 5 HIL, resulting in enhanced luminance. These results suggest that solution-processable V 2 O 5 is a feasible alternative to organic HILs for high-performance QLEDs.

Graphene is highly promising as an electrode for flexible optoelectronic devices due to its excellent conductivity and transparency. However, it is necessary to tailor its work function with a charge injection layer in order to obtain favorable energy level alignment for efficient charge injection. An adequate charge injection layer can only be chosen with the understanding of the interfacial electronic structure between a charge transport layer and an electrode. In this study, we investigated the energy level alignment of N , N ′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB)/hexaazatriphenylene hexacarbonitrile (HAT-CN)/graphene using in situ ultraviolet and X-ray photoelectron spectroscopy measurements. The effective work function of graphene was significantly increased by 0.94 eV by the HAT-CN hole injection layer (HIL) due to the interface dipole formation. In addition, the charge generation barrier (CGB) between NPB and HAT-CN, which plays a decisive role in charge injection efficiency with a charge generation HIL, was measured to be 0.66 eV. This CGB on graphene is the same as the CGBs on other electrodes, and smaller than that of the widely-used MoO 3 HIL. Therefore, HAT-CN could be a promising HIL for efficient flexible organic light-emitting diodes with a graphene anode.

Phototransistors that can be modulated by visible light have been fabricated using ZnO film and CdSe/ZnS quantum dots (QDs). Typical ZnO thin film transistors (TFTs) were fabricated using a solution process, and then small-band-gap QDs, which can absorb low-energy visible light, were coated on the ZnO surface. The device induced strong photocurrent under illumination by visible light, whereas it was difficult to observe any photocurrent under illumination by near infrared light. The small band gap of CdSe/ZnS QDs (1.94 eV) enables the absorption of low-energy photons such as visible light, and excites carriers from a valence band to a conduction band. Then the excited carriers can flow through the conduction band of the ZnO film. Thus, the device could be modulated by visible light (λ = 635 nm); its photoresponsivity was 14,602 A/W. These results represent a useful way to fabricate solution-processed visible-light phototransistors for flexible and transparent electronics.

IC 기판의 가장 중요한 성질들의 하나는 넓은 영역에 걸쳐 균일해야만 한다는 것이다. 웨이퍼 결함 분석의 다양한 물리적 접근 방법 중에서 적외선 조사 기법에 특별한 관심이 모아지고 있다. 특히, 높은 공간적 분해력을 가지고 있는 근적외선 흡수 방법은 반-절연 GaAs 내의 결함들을 직접적으로 관찰하는데 이용되고 있다. 적외선 전송에 기초를 둔 이 기법은 신속하고 비파괴 적이다. 이 방법은, 직접적으로 GaAs 반도체의 적외선 영상은 결함의 광흡수 작용에 기인한 것임을 밝히고 있다. 반-절연 GaAs 내의 EL2에 관련된, 비 균일 적으로 분포된 결함들의 적외선 흡수 영상에서 콘트라스트가 반전되는 현상에 대해 새로운 모델을 제시하고 있다. 저온 포토퀀칭 실험은, 직접적인 방법으로, GaAs 웨이퍼의 콘트라스트 반전 영상은 밴드갭의 지엽적인 변동이나 전하 재분포에 의한 것이 아니라 흡수와 산란의 두 메커니즘에 의한 것임을 증명하고 있다.

The interfacial electronic structure between a W-doped In

(ta-C) films coated through the filtered cathodic vacuum arc (FCVA) process as a hole transport layer (HTL) for perovskite solar cells (PSCs) and quantum dot light-emitting diodes (QDLEDs). The p-type ta-C film has several remarkable features, including ease of fabrication without the need for thermal annealing, reasonable electrical conductivity, optical transmittance, and a high work function. X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy examinations show that the electrical properties (sp3/sp2 hybridized bond) and work function of the ta-C HTL are appropriate for PSCs and QDLEDs. In addition, in order to correlate the performance of the devices, the optical, surface morphological, and structural properties of the FCVA-grown ta-C films with different thicknesses (5 ~ 20 nm) deposited on the ITO anode are investigated in detail. The optimized ta-C film with a thickness of 5 nm deposited on the ITO anode had a sheet resistance of 10.33 Ω−2, a resistivity of 1.34 × 10−4 Ω cm, and an optical transmittance of 88.97%. Compared to the reference PSC with p-NiO HTL, the PSC with 5 nm thick ta-C HTL yielded a higher power conversion efficiency (PCE, 10.53%) due to its improved fill factor. Further, the performance of QDLEDs with 5 nm thick ta-C hole injection layers (HIL) showed better than the performance of QDLEDs with different ta-C thicknesses. It is concluded that ta-C films have the potential to serve as HTL and HIL in next-generation PSCs and QDLEDs., Graphical abstract

Efficiency and operational durability are crucial characteristics for the high-performance quantum-dots light-emitting diodes (QLEDs). In order to improve the efficiency and the stability of the QLEDs, we have inserted an inorganic Al2O3 interfacial modification layer (IML) next to the electron transport layer (ETL) using atomic layer deposition (ALD). We conducted a comparative analysis of two different positions of Al2O3 IML inside the device, inserting IML before ETL and after ETL, to find an optimized structure for the efficient QLEDs. As a result, when Al2O3 IML was located after ETL, reduction of oxygen vacancy in the ZnO layer was occurred due to the reaction of O2 plasma reactant that used during the ALD process. It can have the effects of decreasing the exciton quenching phenomenon and balancing the charge injection. Therefore, improved device performances were observed, and the maximum luminance was 56 108 cd m−2 when 1 nm Al2O3 IML was deposited after ZnO ETL. These results suggest Al2O3 IML deposition would provide a useful way to improve the performance of QLEDs.

The structural properties of HfO₂ films could be improved by thermal treatment owing to their crystallization. We deposited HfO₂ films on sapphire by radio frequency (RF) magnetron sputtering, whose base vacuum pressure was lower than 4.5 × 10 −6 ㎩, RF power was 100 W, working temperature was 200°C, working pressure was 3 mTorr, and the density of the active gas (Argon) was 20 sccm. After depositing the HfO₂ films, the samples were thermally treated by rapid thermal annealing (RTA) in O₂ ambient at different temperatures. Subsequently, the measured physical properties (structural, morphological, and optical) indicated that the crystallite size, refractive index at a wavelength of 632 ㎚, and packing density increased with rising temperatures. In particular, an HfO₂ film thermally treated at 800℃ in O₂ ambient had the highest refractive index of 2.0237 and packing density of 0.9638. The relation between optical and structural properties was also analyzed.

In this paper, the MIS(: Metal-Insulator-Semiconductor) Capacitor with the nitrided-oxide by RTP are fabricated to investigate the carrier trap parameters due to avalanche electron injection. Two times turn-around phenomenon of the flatband voltage shift generated by the avalanche injection are observed. This shows that electron trapping occurs in the oxide film at the first stage. As the electron injection increases, the first turn-around occures due to a positive charge in the oxide layer. After further injection, the curves turns around once again by electron captured. Based on the experimental results, the carrier trapping model for system having multi-traps is proposed and is fitting with experimental data in order to determine trap parameter of nitrided-oxide.