Improvement of the Stability of Quantum-Dot Light Emitting Diodes Using Inorganic HfO Hole Transport Layer.

One of the major challenges in QLED research is improving the stability of the devices. In this study, we fabricated all inorganic quantum-dot light emitting diodes (QLEDs) using hafnium oxide (HfO) as the hole transport layer (HTL), a material commonly used for insulator. Oxygen vacancies in HfO create defect states below the Fermi level, providing a pathway for hole injection.

Wide process temperature of atomic layer deposition for InOthin-film transistors using novel indium precursor (N,N'-di-tert butylacetimidamido)dimethyllindium.

This study introduces a novel heteroleptic indium complex, which incorporates an amidinate ligand, serving as a high-temperature atomic layer deposition (ALD) precursor. The most stable structure was determined using density functional theory and synthesized, demonstrating thermal stability up to 375 °C. We fabricated indium oxide thin-film transistors (InOTFTs) prepared with DBADMI precursor using ALD in wide range of window processing temperature of 200 °C, 300 °C, and 350 °C with an ozone (O) as the source.

Visualizing the Low-Energy Electronic Structure of Prototypical Hybrid Halide Perovskite through Clear Band Measurements.

Organic-inorganic hybrid perovskites (OIHPs) are a promising class of materials that rival conventional semiconductors in various optoelectronic applications. However, unraveling the precise nature of their low-energy electronic structures continues to pose a significant challenge, primarily due to the absence of clear band measurements. Here, we investigate the low-energy electronic structure of CHNHPbI (MAPI) using angle-resolved photoelectron spectroscopy combined with density functional theory.

Self-Assembled TaO/2H-TaS as a van der Waals Platform of a Multilevel Memristor Circuit Integrated with a β-GaO Transistor.

Two-dimensional (2D)-layered material tantalum disulfide (2H-TaS) is known to be a van der Waals conductor at room temperature. Here, 2D-layered TaS has been partially oxidized by utraviolet-ozone (UV-O) annealing to form a 12-nm-thin TaO on conducting TaS, so that the TaO/2H-TaS structure might be self-assembled. Utilizing the TaO/2H-TaS structure as a platform, each device of a β-GaO channel MOSFET and a TaO memristor has been successfully fabricated.

Prospective Cohort Study with a 2-Year Follow-up of Clinical Results, Fusion Rate, and Muscle Bulk for Uniportal Full Endoscopic Posterolateral Transforaminal Lumbar Interbody Fusion.

Study Design: Retrospective cohort study.

Purpose: Postoperative evaluation of the cross-sectional area of paraspinal muscle and clinical findings in patients who had interlaminar route uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion (EPTLIF) after 2 years.

Overview Of Literature: There are limited short-term follow-up studies on efficacy, safety, and physiological changes with a 2-year follow-up.

Remodeling of Epidural Fluid Hematoma after Uniportal Lumbar Endoscopic Unilateral Laminotomy with Bilateral Decompression: Comparative Clinical and Radiological Outcomes with a Minimum Follow-up of 2 Years.

Study Design: Retrospective cohort study.

Purpose: To evaluate the clinical and radiological effects of epidural fluid hematoma in the medium term after lumbar endoscopic decompression.

Overview Of Literature: There is limited literature comparing the effect of postoperative epidural fluid hematoma after uniportal endoscopic decompression.

Remodeling Pattern of Spinal Canal after Full Endoscopic Uniportal Lumbar Endoscopic Unilateral Laminotomy for Bilateral Decompression: One Year Repetitive MRI and Clinical Follow-Up Evaluation.

Objective: There is limited literature on repetitive postoperative MRI and clinical evaluation after Uniportal Lumbar Endoscopic Unilateral Laminotomy for Bilateral Decompression. Methods: Clinical visual analog scale, Oswestry Disability Index, McNab’s criteria evaluation and MRI evaluation of the axial cut spinal canal area of the upper end plate, mid disc and lower end plate were performed for patients who underwent single-level Uniportal Lumbar Endoscopic Unilateral Laminotomy for Bilateral Decompression. From the evaluation of the axial cut MRI, four types of patterns of remodeling were identified: type A: continuous expanded spinal canal, type B: restenosis with delayed expansion, type C: progressive expansion and type D: restenosis.

Observation of 3D Biexcitons in Pristine-Quality CH NH PbBr Single Crystals.

Halide perovskites (HPs) are fascinating materials whose optoelectronic properties are arguably excitonic. In the HP family, biexcitons are known to exist only in low dimensions where exciton-exciton binding is strongly enhanced by quantum and dielectric confinements. In this paper, however, it is shown that they indeed do exist in 3D bulk CH NH PbBr (MAPbBr ) single crystals if the pristine crystal quality is ensured for subtle binding of two excitons.

Damage-Free Charge Transfer Doping of 2D Transition Metal Dichalcogenide Channels by van der Waals Stamping of MoO and LiF.

To dope 2D semiconductor channels, charge-transfer doping has generally been done by thermal deposition of inorganic or organic thin-film layers on top of the 2D channel in bottom-gate field-effect transistors (FETs). The doping effects are reproducible in most cases. However, such thermal deposition will damage the surface of 2D channels due to the kinetic energy of depositing atoms, causing hysteresis or certain degradation.

Commensurate Assembly of C on Black Phosphorus for Mixed-Dimensional van der Waals Transistors.

2D crystals can serve as templates for the realization of new van der Waals (vdW) heterostructures via controlled assembly of low-dimensional functional components. Among available 2D crystals, black phosphorus (BP) is unique due to its puckered atomic surface topography, which may lead to strong epitaxial phenomena through guided vdW assembly. Here, it is demonstrated that a BP template can induce highly oriented assembly of C molecular crystals.

Lithium Polystyrene Sulfonate as a Hole Transport Material in Inverted Perovskite Solar Cells.

Despite the exceptional efficiency of perovskite solar cells (PSCs), further improvements can be made to bring their power conversion efficiencies (PCE) closer to the Shockley-Queisser limit, while the development of cost-effective strategies to produce high-performance devices are needed for them to reach their potential as a widespread energy source. In this context, there is a need to improve existing charge transport layers (CTLs) or introduce new CTLs. In this contribution, we introduced a new polyelectrolyte (lithium poly(styrene sulfonate (PSS))) (Li:PSS) polyelectrolyte as an HTL in inverted PSCs, where Li can act as a counter ion for the PSS backbone.

Dramatic Reduction of Contact Resistance via Ultrathin LiF in Two-Dimensional MoS Field Effect Transistors.

Molybdenum disulfide (MoS) has been regarded as one of the most important n-type two-dimensional (2D) transition metal dichalcogenide semiconductors for nanoscale electron devices. Relatively high contact resistance () remains as an issue in the 2D-devices yet to be resolved. Reliable technique is very compelling to practically produce low values in device electronics, although scientific approaches have been made to obtain a record-low .

High-Performance van der Waals Junction Field-Effect Transistors Utilizing Organic Molecule/Transition Metal Dichalcogenide Interface.

Two-dimensional (2D) transition metal dichalcogenide (TMD) hetero PN junctions with a van der Waals (vdW) interface have received much attention, because PN diodes are basically important to control the vertical current across the junction. Interestingly, the same vdW PN junction structure can be utilized for junction field-effect transistors (JFETs) where in-plane current is controlled along the junction. However, 2D vdW JFETs seem rarely reported, despite their own advantages to achieve when good vdW junction is secured.

Enhanced Photoinduced Carrier Generation Efficiency through Surface Band Bending in Topological Insulator BiSe Thin Films by the Oxidized Layer.

Topological insulators (TIs) have become popular in the field of optoelectronic devices because of their broadband and high-sensitivity properties, which are attributed to the narrow band gap of the bulk state and high mobility of the Dirac surface state. Although perfectly grown TIs are known to exhibit strong stability against oxidation, in most cases, the existence of vacancy defects in TIs reacts to air and the characteristics of TIs is affected by oxidation. Therefore, changes in the band structure and electrical characteristics by oxidation should be considered.

Self-Powered Visible-Invisible Multiband Detection and Imaging Achieved Using High-Performance 2D MoTe/MoS Semivertical Heterojunction Photodiodes.

Two-dimensional (2D) van der Waals (vdW) heterostructures herald new opportunities for conducting fundamental studies of new physical/chemical phenomena and developing diverse nanodevice applications. In particular, vdW heterojunction p-n diodes exhibit great potential as high-performance photodetectors, which play a key role in many optoelectronic applications. Here, we report on 2D MoTe/MoS multilayer semivertical vdW heterojunction p-n diodes and their optoelectronic application in self-powered visible-invisible multiband detection and imaging.

Band Alignment Engineering between Planar SnO and Halide Perovskites via Two-Step Annealing.

Managing defects in SnO is critical for improving the power conversion efficiency (PCE) of halide perovskite-based solar cells. However, typically reported SnObased perovskite solar cells have inherent defects in the SnO layer, which lead to a lower PCE and hysteresis. Here, we report that a dual-coating approach for SnO with different annealing temperatures can simultaneously form a SnO layer with high crystallinity and uniform surface coverage.

Optimization of the electron transport in quantum dot light-emitting diodes by codoping ZnO with gallium (Ga) and magnesium (Mg).

In our study, to optimize the electron-hole balance through controlling the electron transport layer (ETL) in the QD-LEDs, four materials (ZnO, ZnGaO, ZnMgO, and ZnGaMgO NPs) were synthesized and applied to the QD-LEDs as ETLs. By doping ZnO NPs with Ga, the electrons easily inject due to the increased Fermi level of ZnO NPs, and as Mg is further doped, the valence band maximum (VBM) of ZnO NPs deepens and blocks the holes more efficiently. Also, at the interface of QD/ETLs, Mg reduces non-radiative recombination by reducing oxygen vacancy defects on the surface of ZnO NPs.

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

We have investigated a series of non-conjugated polyelectrolytes (NPEs) which are based on a polyethylenimine (PEI) backbone with various counterions, such as Br I and BIm , as interfacial layers at the electrodes of solar cells and transistor devices to improve the power conversion efficiency (PCE) and device performance. This new series of NPEs with different counterions are capable of forming electric dipoles at NPE/metal electrode interfaces; as a consequence tuning of the energy levels, and work function (WF) of the electrodes is possible. Using this approach, the PCE of organic solar cells could be improved from 1.

ZnO:Ga-graded ITO electrodes to control interface between PCBM and ITO in planar perovskite solar cells.

Ga-doped ZnO (GZO)-graded layer, facilitating electron extraction from electron transport layer, was integrated on the surface of transparent indium tin oxide (ITO) cathode by using graded sputtering technique to improve the performance of planar n-i-p perovskite solar cells (PSCs). The thickness of graded GZO layer was controlled to optimize GZO-indium tin oxide (ITO) combined electrode for planar n-i-p PSCs. At optimized graded thickness of 15 nm, the GZO-ITO combined electrode showed an optical transmittance of 95%, a resistivity of 2.

Electronic Structure of Nonionic Surfactant-Modified PEDOT:PSS and Its Application in Perovskite Solar Cells with Reduced Interface Recombination.

The interfacial properties of organolead halide perovskite solar cells (PSCs) affect the exciton and charge-transport dynamics significantly. Thus, proper modification of the interfaces between perovskite and charge-transport layers is an efficient method to increase the power conversion efficiency (PCE) of PSCs. In this work, we explore the effect of a nonionic surfactant, that is, Triton X-100 (TX) additive, in the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole-transport layer.

Interfacial electronic structure between a W-doped InO transparent electrode and a VO hole injection layer for inorganic quantum-dot light-emitting diodes.

The interfacial electronic structure between a W-doped InO (IWO) transparent electrode and a VO 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 VO HIL at 1.0 eV below the Fermi level.

Design of InZnSnO Semiconductor Alloys Synthesized by Supercycle Atomic Layer Deposition and Their Rollable Applications.

Amorphous InGaZnO semiconductors have been rapidly developed as active charge-transport materials in thin film transistors (TFTs) because of their cost effectiveness, flexibility, and homogeneous characteristics for large-area applications. Recently, InZnSnO (IZTO) with superior mobility (higher than 20 cm V s) has been suggested as a promising oxide semiconductor material for high-resolution, large-area displays. However, the electrical and physical characteristics of IZTO have not been fully characterized.