Triple-Stack ZnO/AlZnO/YZnO Heterojunction Oxide Thin-Film Transistors by Spray Pyrolysis for High Mobility and Excellent Stability

We demonstrate a high mobility, triple-stack ZnO/AlZnO/YZnO heterojunction thin-film transistor (TFT) using the semiconductors deposited by spray pyrolysis at 350 °C on an Al₂O₃ gate insulator. A thin layer (5 nm) of AlZnO on the top of ZnO used as an active layer of an inverted coplanar-structured TFT increases the field-effect mobility (μ_FE) from 42.56 to 82.7 cm² V^-1 s^-1. An additional 5 nm thick YZnO on the top of the ZnO/AlZnO TFT improves the electrical stability by reducing the defects in the bulk ZnO, AlZnO, and at the interface AlO_x/ZnO. The ZnO-based materials show a nanocrystalline structure with the grain size less than 20 nm. The triple-stack oxide TFT shows a μ_FE of 71.3 cm² V^-1 s^-1 with a threshold voltage (V_TH) of 2.85 V. The hysteresis voltage for pristine ZnO, ZnO/AlZnO, and ZnO/AlZnO/YZnO TFTs is 0.52, 0.24, and 0.02 V, respectively. The ZnO/AlZnO/YZnO TFT shows a negligible V_TH shift under temperature bias stress for 3600 s at 60 °C and excellent environmental stability over a few months, which is due to the presence of stronger Y-O and Al-O bonds in the back channel. The threshold voltage shift under positive bias temperature stress for pristine ZnO, ZnO/AlZnO, and ZnO/AlZnO/YZnO TFTs is 0.78, 0.40, and 0.15 V, respectively. Compared to the pristine ZnO TFT, the ZnO/AlZnO/YZnO TFT shows better environmental and bias stabilities with improved hysteresis. The experimental data of ZnO/AlZnO and ZnO/AlZnO/YZnO TFTs can be fitted by technology computer-aided design (TCAD) simulation using the density of states model of the oxide semiconductors. From the TCAD simulation, it is found that a 2D-like electron gas is formed at the narrow AlZnO layer between ZnO and YZnO.

High efficiency blue organic light-emitting diodes with below-bandgap electroluminescence

Blue organic light-emitting diodes require high triplet interlayer materials, which induce large energetic barriers at the interfaces resulting in high device voltages and reduced efficiencies. Here, we alleviate this issue by designing a low triplet energy hole transporting interlayer with high mobility, combined with an interface exciplex that confines excitons at the emissive layer/electron transporting material interface. As a result, blue thermally activated delay fluorescent organic light-emitting diodes with a below-bandgap turn-on voltage of 2.5 V and an external quantum efficiency (EQE) of 41.2% were successfully fabricated. These devices also showed suppressed efficiency roll-off maintaining an EQE of 34.8% at 1000 cd m⁻². Our approach paves the way for further progress through exploring alternative device engineering approaches instead of only focusing on the demanding synthesis of organic compounds with complex structures.

Thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs) rely on high triplet energy interlayers to confine excitons, which results in reduced performance. Here, the authors report high-performance blue TADF-OLEDs with below bandgap electroluminescence.

High Performance of Solution-Processed Amorphous p-Channel Copper-Tin-Sulfur-Gallium Oxide Thin-Film Transistors by UV/O3 Photocuring

The development of p-type metal-oxide semiconductors (MOSs) is of increasing interest for applications in next-generation optoelectronic devices, display backplane, and low-power-consumption complementary MOS circuits. Here, we report the high performance of solution-processed, p-channel copper-tin-sulfide-gallium oxide (CTSGO) thin-film transistors (TFTs) using UV/O₃ exposure. Hall effect measurement confirmed the p-type conduction of CTSGO with Hall mobility of 6.02 ± 0.50 cm² V^-1 s^-1. The p-channel CTSGO TFT using UV/O₃ treatment exhibited the field-effect mobility (μ_FE) of 1.75 ± 0.15 cm² V^-1 s^-1 and an on/off current ratio (I_ON/I_OFF) of ∼10⁴ at a low operating voltage of -5 V. The significant enhancement in the device performance is due to the good p-type CTSGO material, smooth surface morphology, and fewer interfacial traps between the semiconductor and the Al₂O₃ gate insulator. Therefore, the p-channel CTSGO TFT can be applied for CMOS MOS TFT circuits for next-generation display.

Determination of in vitro dry matter, protein, and fiber digestibility and fermentability of novel corn coproducts for swine and ruminants

New processes are being used in some dry-grind ethanol plants in the United States and Brazil to improve ethanol yield and efficiency of production while also providing nutritionally enhanced corn coproducts compared with conventional corn distillers dried grains with solubles (DDGS). The objectives of this study were to determine the chemical composition and in vitro digestibility of 5 conventional corn DDGS sources and 10 emerging novel corn coproducts for swine and ruminants, and compare coproducts produced using similar processes in the United States and Brazil. Chemical composition, on a dry matter (DM) basis, among the 15 coproducts ranged from 18.5% to 54.7% for crude protein (CP), 12.3% to 51.4% for neutral detergent fiber (NDF), 1.6% to 8.6% for acid detergent fiber, 4.7% to 12.3% for ether extract, and 1.6% to 8.6% for ash. For swine, in vitro hydrolysis of DM and CP were greater (P < 0.01) for the three U.S. corn DDGS sources compared with the two Brazilian corn DDGS sources, but in vitro fermentability of DM was comparable (P > 0.05) among all sources except one U.S. DDGS source that had less fermentable DM. High-protein and yeast dried distillers grains (Ultramax, UM; StillPro, SP) coproducts also had comparable (P > 0.05) DM fermentability for swine, but UM coproducts had greater (P < 0.01) DM and CP hydrolysis compared with SP. High-protein distillers dried grains (HP-DDG) from Brazil had greater (P < 0.01) DM and CP hydrolysis, but less (P < 0.01) DM fermentability for swine than HP-DDG produced in the United States, using the same process. For ruminants, total DM digestibility was greater (P < 0.01) in conventional DDGS sources from the United States compared with the two DDGS sources from Brazil. Total protein digestibility for ruminants was comparable and above 81% for all coproducts except for a DDGS source from Brazil, a HP-DDG source from the United States, and a UM sample. Interestingly, the corn fiber + solubles coproduct had not only relatively high digestibility of NDF (67.9%), DM (91.6%), and total CP (81.9%) for ruminants, but it also had relatively high total tract digestibility of DM (86.2%) and CP (69.9%) for swine. These results suggest that nutrient digestibility of conventional DDGS sources produced in the United States appear to be greater than corn Brazilian DDGS sources, but new process technologies being implemented in ethanol and coproduct production in both countries can enhance the nutritional value of corn coproducts for both swine and ruminants.

Free-standing nanopaper electrode for all-printed super-flexible perovskite solar cells.. [DOI: 10.21203/rs.3.rs-296909/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The development of all-printed, flexible solar cells of high efficiency and ultra-low weight will offer advancements for new market entrants. Herein, we report the design and fabrication of all-printed in ambient air, super-flexible perovskite solar cells with approaching 20% power conversion efficiency and extremely low weight of 5.1 g m-2 leading to an unprecedented power-to-weight ratio of 38,470 W Kg-1. This performance advance was achieved through the design of a highly transparent and conducting nanopaper used as a free-standing bottom electrode (FSBE). The FSBE consisted of cellulose nanocrystals grafted with semi-metallic super-reduced polyoxometalate clusters that enabled high conductivities up to 18 S cm-1 combined with transparency >96%. It also acted as a conformal barrier preventing performance loss upon heating at 95 oC under continuous illumination in inert environment; and strong resistance to decomposition when immersed in a mild citric acid water solution for 100 days, which we further exploit to demonstrate full device recyclability. The inherent flexibility of cellulose nanocrystals enabled remarkable flexibility of these cells under 2,000 repeated bending and folding cycles and mechanical strength upon extensive strain up to 20%. Notably, the nanopaper remained unaffected for strains up to 60%. These findings open the door for efficient and lightweight solar cells with a low environmental impact.

Stability of Quantum-Dot Light Emitting Diodes with Alkali Metal Carbonates Blending in Mg Doped ZnO Electron Transport Layer

We report here the fabrication of highly efficient and long-lasting quantum-dot light emitting diodes (QLEDs) by blending various alkali metal carbonate in magnesium (Mg) doped zinc oxide (ZnO) (MZO) electron transport layer (ETL). Alkali metal carbonates blending in MZO, X2CO3:MZO, control the band-gap, electrical properties, and thermal stability. This can therefore enhance the operational lifetime of QLEDs. It is found that the conductivity of X2CO3:MZO film can be controlled and the thermal stability of ETLs could be improved by X2CO3 blending in MZO. The inverted red QLEDs (R-QLEDs) with Cs2CO3:MZO, Rb2CO3:MZO, and K2CO3:MZO ETLs exhibited the operational lifetime of 407 h for the R-QLEDs with Cs2CO3:MZO, 620 h with Rb2CO3:MZO and 94 h with K2CO3:MZO ETLs at T95 with the initial luminance of 1000 cd/m2. Note that all red QLEDs showed the high brightness over 150,000 cd/m2. But the R-QLEDs with Na2CO3:MZO and Li2CO3:MZO ETLs exhibited shorter operational lifetime and poor brightness than the R-QLED with pristine MZO ETL.

Prediction of Human Papillomavirus Status and Overall Survival in Patients with Untreated Oropharyngeal Squamous Cell Carcinoma: Development and Validation of CT-Based Radiomics

BACKGROUND AND PURPOSE

Human papillomavirus is a prognostic marker for oropharyngeal squamous cell carcinoma. We aimed to determine the value of CT-based radiomics for predicting the human papillomavirus status and overall survival in patients with oropharyngeal squamous cell carcinoma.

MATERIALS AND METHODS

Eighty-six patients with oropharyngeal squamous cell carcinoma were retrospectively collected and grouped into training (n = 61) and test (n = 25) sets. For human papillomavirus status and overall survival prediction, radiomics features were selected via a random forest-based algorithm and Cox regression analysis, respectively. Relevant features were used to build multivariate Cox regression models and calculate the radiomics score. Human papillomavirus status and overall survival prediction were assessed via the area under the curve and concordance index, respectively. The models were validated in the test and The Cancer Imaging Archive cohorts (n = 78).

RESULTS

For prediction of human papillomavirus status, radiomics features yielded areas under the curve of 0.865, 0.747, and 0.834 in the training, test, and validation sets, respectively. In the univariate Cox regression, the human papillomavirus status (positive: hazard ratio, 0.257; 95% CI, 0.09-0.7; P = .008), T-stage (≥III: hazard ratio, 3.66; 95% CI, 1.34-9.99; P = .011), and radiomics score (high-risk: hazard ratio, 3.72; 95% CI, 1.21-11.46; P = .022) were associated with overall survival. The addition of the radiomics score to the clinical Cox model increased the concordance index from 0.702 to 0.733 (P = .01). Validation yielded concordance indices of 0.866 and 0.720.

CONCLUSIONS

CT-based radiomics may be useful in predicting human papillomavirus status and overall survival in patients with oropharyngeal squamous cell carcinoma.

Lanthanum Doping in Zinc Oxide for Highly Reliable Thin-Film Transistors on Flexible Substrates by Spray Pyrolysis

Solution-processed metal-oxide thin-film transistors (TFTs) are considered as one of the most favorable devices for next-generation, large-area flexible electronics. In this paper, we demonstrate the excellent material properties of lanthanum-zinc oxide (LaZnO) thin films deposited by spray pyrolysis and their application to TFTs. The threshold voltage of the LaZnO TFTs shifts toward positive gate voltage, and the mobility decreases with increasing lanthanum ratio in ZnO from 0 to 20%. The purification of the LaZnO precursor (P-LaZnO) further improves the device performance. The P-LaZnO TFT exhibits a field-effect mobility of 22.43 cm² V^-1 s^-1, zero hysteresis voltage, and negligible threshold voltage V_TH shift under positive bias temperature stress. The enhancement in the electrical properties is due to a decrease in grain size, smooth surface roughness, and reduction in the trap density in the LaZnO film. X-ray photoelectron spectroscopy (XPS) results confirm the presence of La in the TFT channel and at/near the interface of the LaZnO and ZrO_x gate insulator, leading to fewer interfacial traps. The flexible P-LaZnO TFT fabricated on the polyimide substrate exhibits a mobility of 17.64 cm² V^-1 s^-1 and a negligible V_TH shift under bias stress. Also, the inverter made of LZO TFTs is working well with a voltage gain of 17.74 (V/V) at 4 V. Therefore, the LaZnO TFT is a promising device for next-generation flexible displays.

Biocatalytic Production of a Potent Inhibitor of Adipocyte Differentiation from Phloretin Using Engineered CYP102A1

In this study, we investigated an efficient enzymatic strategy for producing potentially valuable phloretin metabolites from phlorizin, a glucoside of phloretin that is rich in apple pomace. Almond β-glucosidase efficiently removed phlorizin's glucose moiety to produce phloretin. CYP102A1 engineered by site-directed mutagenesis, domain swapping, and random mutagenesis catalyzed the highly regioselective C-hydroxylation of phloretin into 3-OH phloretin with high conversion yields. Under the optimal hydroxylation conditions of 15 g cells L^-1 and a 20 mM substrate for whole-cell biocatalysis, phloretin was regioselectively hydroxylated into 3.1 mM 3-OH phloretin each hour. Furthermore, differentiation of 3T3-L1 preadipocytes into adipocytes and lipid accumulation were dramatically inhibited by 3-OH phloretin but promoted by phloretin. Consistent with these inhibitory effects, the expression of adipogenic regulator genes was downregulated by 3-OH phloretin. We propose a platform for the sustainable production and value creation of phloretin metabolites from apple pomace capable of inhibiting adipogenesis.

Significant Performance and Stability Improvements of Low-Temperature IGZO TFTs by the Formation of In-F Nanoparticles on an SiO2 Buffer Layer

We report the performance improvement of low-temperature coplanar indium–gallium–zinc–oxide (IGZO) thin-film transistors (TFTs) with a maximum process temperature of 230 °C. We treated F plasma on the surface of an SiO₂ buffer layer before depositing the IGZO semiconductor by reactive sputtering. The field-effect mobility increases from 3.8 to 9.0 cm² V⁻¹·s⁻¹, and the threshold voltage shift (ΔV_th) under positive-bias temperature stress decreases from 3.2 to 0.2 V by F-plasma exposure. High-resolution transmission electron microscopy and atom probe tomography analysis reveal that indium fluoride (In-F) nanoparticles are formed at the IGZO/buffer layer interface. This increases the density of the IGZO and improves the TFT performance as well as its bias stability. The results can be applied to the manufacturing of low-temperature coplanar oxide TFTs for oxide electronics, including information displays.

Significant improvement of spray pyrolyzed ZnO thin film by precursor optimization for high mobility thin film transistors

Metal-oxide thin-film transistors (TFT) fabricated by spray pyrolysis are of increasing interest because of its simple process and scalability. A bottleneck issue is to get a bubble-free and dense material. We studied the effect of ammonium acetate (AA) addition in the oxide precursor solution on the performance of spray-coated ZnO TFTs. AA acts as a stabilizer, which increases the solubility of the solution and enhances the film quality by reducing the defects. With AA addition in ZnO precursor, the films are coffee ring free with high mass density and better grain orientation. The ZnO TFT with AA exhibit a remarkable improvement of its device performance such as saturation mobility increasing from 5.12 to 41.53 cm²V⁻¹s⁻¹, the subthreshold swing decreasing from 340 to 162 mV/dec and on/off current ratio increasing from ~10⁵ to 10⁸. Additionally, the TFTs show excellent stability with a low threshold voltage shift of 0.1 V under gate bias stress. Therefore, the addition of AA is a promising approach to achieve high-performance ZnO TFTs for low-cost manufacturing of displays.

0047 The Change in Melatonin Rhythm Depending on Dementia Severity in Alzheimer’s Disease (AD) Patients

Introduction

In Alzheimer’s disease (AD), both sleep and circadian dysfunctions are commonly reported and these are associated with neurodegenerative change. Actually, it has been reported that changes in circadian rhythms in AD were apparently discrete from those seen in normal aging. Previous studies reported the delayed phase in the activity or core body temperature rhythms in severe AD patients compared to normal controls. However, it is unknown whether similar changes in melatonin rhythms occur in AD patients who were not severely demented. We aimed to compare melatonin rhythms depending on dementia severity in mild and moderate AD patients.

Methods

We recruited AD patients of mild or moderate degree who had the Pittsburgh Sleep Quality Index (PSQI) score of 5 or greater and/or complained insomnia symptoms more than 3 times a week for a month. The patients were classified according to their Clinical Dementia Rating (CDR) score into 3 groups (CDR=0.5, 1, 2). The dim light melatonin onset (DLMO) was determined from seven hourly saliva samples obtained in the laboratory prior to sleep onset measured by actigraphy. The phase angle between the DLMO and sleep onset (PA-SO), and that between the DLMO and midsleep time (PA-MST) were calculated. Each group included 13, 13 and 6 AD patients with the CDR score of 0.5, 1 and 2, respectively. The DLMO and PA were compared among the 3 groups, and correlation analyses of the DLMO and PA with the MMSE in the Korean version of CERAD Packet (MMSE-KC) scores were done in total patients.

Results

There was no significant difference in the DLMO and PA between the 3 groups. The MMSE-KC score was positively correlated with the DLMO and negatively correlated with the PA-MST.

Conclusion

There were no changes in melatonin rhythms according to dementia severity in mild and moderate AD patients with sleep complaints. However, our study showed that earlier melatonin phase was associated with more impaired cognitive function.

Support

Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2017R1A2B4003493)

Amorphous Tin Oxide Applied to Solution Processed Thin-Film Transistors

The limited choice of materials for large area electronics limits the expansion of applications. Polycrystalline silicon (poly-Si) and indium gallium zinc oxide (IGZO) lead to thin-film transistors (TFTs) with high field-effect mobilities (>10 cm²/Vs) and high current ON/OFF ratios (I_On/I_Off > ~10⁷). But they both require vacuum processing that needs high investments and maintenance costs. Also, IGZO is prone to the scarcity and price of Ga and In. Other oxide semiconductors require the use of at least two cations (commonly chosen among Ga, Sn, Zn, and In) in order to obtain the amorphous phase. To solve these problems, we demonstrated an amorphous oxide material made using one earth-abundant metal: amorphous tin oxide (a-SnO_x). Through XPS, AFM, optical analysis, and Hall effect, we determined that a-SnO_x is a transparent n-type oxide semiconductor, where the SnO₂ phase is predominant over the SnO phase. Used as the active material in TFTs having a bottom-gate, top-contact structure, a high field-effect mobility of ~100 cm²/Vs and an I_On/I_Off ratio of ~10⁸ were achieved. The stability under 1 h of negative positive gate bias stress revealed a Vth shift smaller than 1 V.

Image Quality of Low-Dose Cerebral Angiography and Effectiveness of Clinical Implementation on Diagnostic and Neurointerventional Procedures for Intracranial Aneurysms

BACKGROUND AND PURPOSE

Awareness of the potential for exposure to high doses of radiation from interventional radiologic procedures has increased. The purpose of this study was to evaluate image quality and dose reduction of low-dose cerebral angiography during diagnostic and therapeutic procedures for intracranial aneurysms.

MATERIALS AND METHODS

A retrospective review of 1137 prospectively collected patients between January 2012 and June 2014 was performed. Beginning in April 2013, a dose-reduction strategy was implemented. Subjective image-quality assessment of 506 standard and 540 low-dose cerebral angiography images was performed by 2 neuroradiologists using a 5-point scale and was tested using noninferiority statistics. Radiation dose-area product and air kerma of 1046 diagnostic and 317 therapeutic procedures for intracranial aneurysms were analyzed and compared between groups before (group 1) and after (group 2) clinical implementation of a dose-reduction strategy.

RESULTS

The image quality of the low-dose cerebral angiography was not inferior on the basis of results from the 2 readers. For diagnostic cerebral angiography, the mean dose-area product and air kerma were 140.8 Gy×cm² and 1.0 Gy, respectively, in group 1 and 82.0 Gy×cm² and 0.6 Gy in group 2 (P < .001, P < .001). For the neurointerventional procedure, the mean dose-area product and air kerma were 246.0 Gy×cm² and 3.7 Gy, respectively, in group 1 and 169.8 Gy×cm² and 3.3 Gy in group 2 (P < .001, P = .291).

CONCLUSIONS

With low-dose cerebral angiography, image quality was maintained, and implementation of dose-reduction strategies reduced radiation doses in patients undergoing diagnostic and neurointerventional procedures for intracranial aneurysms.

Polystyrene enhanced crystallization of perovskites towards high performance solar cells

Perovskite solar cells have attracted significant attention due to their high efficiency and low cost. In the research on methylammonium lead-iodide (CH₃NH₃PbI₃), a lot of work has been devoted to optimize the film morphology and crystallinity resulting in an enhancement of the power conversion efficiency (PCE). A good surface coverage and uniform perovskite films are highly desirable along with a smooth and pinhole-free contact between the hole and electron extraction layers. Overall, this affects the charge transport and collection, and reduces charge recombination. Herein, we demonstrate a facile route to control perovskite crystallization by inserting an optimal amount of insulating polystyrene in the perovskite precursor solutions. The incorporation of a small amount of polystyrene results in much better surface coverage, and a smoother and uniform perovskite thin film leading to improved crystallization and larger grain size. Via careful optimization, and easy and low temperature solution-based processing, below 100 °C, we realize a device with PCE exceeding 13% along with significantly reduced leakage current.

Surface Engineering of Room Temperature-Grown Inorganic Perovskite Quantum Dots for Highly Efficient Inverted Light-Emitting Diodes

Inorganic cesium lead bromide quantum dots (CsPbBr₃ QDs) are usually synthesized via a high-temperature process (hot injection, HI). This process is similar to that used for the synthesis of other semiconductor QDs (i.e., CdSe@ZnS), which limits their potential cost advantage. CsPbBr₃ QDs can also be synthesized at room temperature (RT) in a low cost and easily scalable process, which, thus, is one of the greatest advantages of the CsPbBr₃ QDs. However, light-emitting diodes (LEDs) fabricated using RT-QDs exhibit poor performance compared to those of HI-QDs. In fact, QDs are surrounded by insulating ligands to maintain their colloidal stability but these ligands need to be removed to obtain high-performance LEDs. Here, we show that ligand removal techniques used for HI-QDs are not sufficient in the case of RT-QDs. Additional ligand engineering and annealing steps are necessary to remove the excess of ligands from RT-QD films while preventing the coalescence of the QDs. The eventual surface defects induced by annealing can be healed by a subsequent photoactivation step. Moreover, the use of solution processable inorganic charge transport layers can reduce the fabrication costs of LEDs. We fabricated an inverted LED based on a metal oxide electron transport layer and a RT-QD emitting layer which exhibited a maximum current efficiency of 17.61 cd A^-1 and a maximum luminance of 22 825 cd m^-2.