New Bipolar Host Materials Based on Indolocarbazole for Red Phosphorescent OLEDs.

We designed and synthesized new indolocarbazole-triazine derivatives, 9-di-tert-butyl-5,7-bis(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5,7-dihydroindolo[2,3-b]carbazole (2TRZ-P-ICz) and 3,9-di-tert-butyl-5,7-bis(5'-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1':3',1″-terphenyl]-2'-yl)-5,7-dihydroindolo[2,3-b]carbazole (2TRZ-TP-ICz), as new bipolar host materials for red phosphorescent OLEDs. In the film state, 2TRZ-P-ICz and 2TRZ-TP-ICz exhibited photoluminescence maxima at 480 nm and 488 nm, respectively. The dipole moment characteristics of the new compounds under various solvent conditions were investigated using the Lippert-Mataga equation. The results showed that the dipole moment of 2TRZ-P-ICz is 26.9D, while that of 2TRZ-TP-ICz is 21.3D. The delayed fluorescence lifetimes were 0.188 µs for 2TRZ-P-ICz and 2.080 µs for 2TRZ-TP-ICz, with 2TRZ-TP-ICz showing TADF characteristics. Additionally, 2TRZ-TP-ICz was found to have a ΔEST of less than 0.2 eV. The triplet energy levels of the newly synthesized bipolar host materials were found to be 2.72 and 2.75 eV, confirming their suitability for use in red phosphorescent OLEDs. To investigate the carrier mobility of the synthesized materials, hole-only devices and electron-only devices were fabricated and tested. The hole mobility value at 1V was found to be 3.43 × 10-3 cm2/Vs for 2TRZ-P-ICz and 2.16 × 10-3 cm2/Vs for 2TRZ-TP-ICz. For electron mobility at 1V, 2TRZ-P-ICz showed a value of 4.41 × 10-9 cm2/Vs, while 2TRZ-TP-ICz exhibited a value of 9.13 × 10-9 cm2/Vs. As a result, when the new material was used as a host in red phosphorescent OLEDs, 2TRZ-TP-ICz achieved a current efficiency of 9.92 cd/A, an external quantum efficiency of 13.7%, CIE coordinates of (0.679, 0.319), and an electroluminescence maximum wavelength of 626 nm.

Improving the Electroluminescence Properties of New Chrysene Derivatives with High Color Purity for Deep-Blue OLEDs.

Two blue-emitting materials, 4-(12-([1,1':3',1″-terphenyl]-5'-yl)chrysen-6-yl)-N,N-diphenylaniline (TPA-C-TP) and 6-([1,1':3',1″-terphenyl]-5'-yl)-12-(4-(1,2,2-triphenylvinyl)phenyl)chrysene (TPE-C-TP), were prepared with the composition of a chrysene core moiety and terphenyl (TP), triphenyl amine (TPA), and tetraphenylethylene (TPE) moieties as side groups. The maximum photoluminescence (PL) emission wavelengths of TPA-C-TP and TPE-C-TP were 435 and 369 nm in the solution state and 444 and 471 nm in the film state. TPA-C-TP effectively prevented intermolecular packing through the introduction of TPA, a bulky aromatic amine group, and it showed an excellent photoluminescence quantum yield (PLQY) of 86% in the film state. TPE-C-TP exhibited aggregation-induced emission; the PLQY increased dramatically from 0.1% to 78% from the solution state to the film state. The two synthesized materials had excellent thermal stability, with a high decomposition temperature exceeding 460 °C. The two compounds were used as emitting layers in a non-doped device. The TPA-C-TP device achieved excellent electroluminescence (EL) performance, with Commission Internationale de L'Eclairage co-ordinates of (0.15, 0.07) and an external quantum efficiency of 4.13%, corresponding to an EL peak wavelength of 439 nm.

S-LIGHT: Synthetic Dataset for the Separation of Diffuse and Specular Reflection Images.

Several studies in computer vision have examined specular removal, which is crucial for object detection and recognition. This research has traditionally been divided into two tasks: specular highlight removal, which focuses on removing specular highlights on object surfaces, and reflection removal, which deals with specular reflections occurring on glass surfaces. In reality, however, both types of specular effects often coexist, making it a fundamental challenge that has not been adequately addressed. Recognizing the necessity of integrating specular components handled in both tasks, we constructed a specular-light (S-Light) DB for training single-image-based deep learning models. Moreover, considering the absence of benchmark datasets for quantitative evaluation, the multi-scale normalized cross correlation (MS-NCC) metric, which considers the correlation between specular and diffuse components, was introduced to assess the learning outcomes.

Enhancing OLED emitter efficiency through increased rigidity.

Three new blue materials, TPI-InCz, PAI-InCz, and CN-PAI-InCz, have been developed. In the film state, TPI-InCz and PAI-InCz exhibited emission peaks at 411 and 431 nm indicating deep blue emission. CN-PAI-InCz showed a peak emission at 452 nm, within the real blue region. When these three materials were used as the emissive layer to fabricate non-doped devices, CN-PAI-InCz showed the highest current efficiency of 2.91 cd A-1, power efficiency of 1.93 lm W-1, and external quantum efficiency of 3.31%. Among the synthesized materials, CN-PAI-InCz exhibited superior charge balance due to the introduction of CN groups, as confirmed by hole-only devices and electron-only devices. PAI-InCz demonstrated fast hole mobility with a value of 1.50 × 10-3 cm2 V-1 s-1, attributed to its planar and highly rigid structure. In the resulting devices, the Commission Internationale de l'Eclairage coordinates for TPI-InCz, PAI-InCz, and CN-PAI-InCz were (0.162, 0.048), (0.0161, 0.067), and (0.155, 0.099), all indicating emission in the blue region.

Enhancement of Optical and Chemical Resistance Properties with a Novel Yellow Quinophthalone Derivative for Image Sensor Colorants.

A novel quinophthalone derivative, 4,5,6,7-tetrachloro-2-(2-(3-hydroxy-1-oxo-1H-cyclopenta[b]naphthalen-2-yl)quinolin-4-yl)isoindoline-1,3-dione (TCHCQ), was designed and synthesized as a yellow colorant additive for green color filters in image sensors. The characteristics of the new material were evaluated in terms of optical, thermal, and chemical properties under solution and color filter film conditions. TCHCQ exhibited a significantly enhanced molar extinction coefficient in solution, being 1.21 times higher than that of the commercially used yellow colorant Y138. It also demonstrated excellent thermal stability, with a decomposition temperature (Td) exceeding 450 °C. Utilizing the nano-pigmentation process, TCHCQ was used to prepare nano-sized particles with an excellent average size of 35 nm. This enabled the fabrication of a color filter film with outstanding properties. The optical properties of the produced film revealed outstanding yellow colorant transmittance of 0.97% at 435 nm and 91.2% at 530 nm. The color filter film exhibited similar optical and thermal stability to Y138, with an improved chemical stability, as evidenced by a ΔEab value of 0.52. The newly synthesized TCHCQ is considered a promising candidate for use as a yellow colorant additive in image sensor color filters, demonstrating superior optical, thermal, and chemical stability.

Effects of thermal annealing on analog resistive switching behavior in bilayer HfO2/ZnO synaptic devices: the role of ZnO grain boundaries.

The effects of thermal annealing on analog resistive switching behavior in bilayer HfO2/ZnO synaptic devices were investigated. The annealed active ZnO layer between the top Pd electrode and the HfO2 layer exhibited electroforming-free resistive switching. In particular, the switching uniformity, stability, and reliability of the synaptic devices were dramatically improved via thermal annealing at 600 °C atomic force microscopy and X-ray diffraction analyses revealed that active ZnO films demonstrated increased grain size upon annealing from 400 °C to 700 °C, whereas the ZnO film thickness and the annealing of the HfO2 layer in bilayer HfO2/ZnO synaptic devices did not profoundly affect the analog switching behavior. The optimized thermal annealing at 600 °C in bilayer HfO2/ZnO synaptic devices dramatically improved the nonlinearity of long-term potentiation/depression properties, the relative coefficient of variation of the asymmetry distribution σ/µ, and the asymmetry ratio, which approached 1. The results offer valuable insights into the implementation of highly robust synaptic devices in neural networks.

A High-Efficiency Deep Blue Emitter for OLEDs with a New Dual-Core Structure Incorporating ETL Characteristics.

In this study, we introduced the weak electron-accepting oxazole derivative 4,5-diphenyl-2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)oxazole (TPO) into both anthracene and pyrene moieties of a dual core structure. Ultimately, we developed 2-(4-(6-(anthracen-9-yl)pyren-1-yl)phenyl)-4,5-diphenyloxazole (AP-TPO) as the substitution on the second core, pyrene, and 4,5-diphenyl-2-(4-(10-(pyren-1-yl)anthracen-9-yl)phenyl)oxazole (TPO-AP) as the substitution on the first core, anthracene. Both materials exhibited maximum photoluminescence wavelengths at 433 and 443 nm in solution and emitted deep blue light with high photoluminescence quantum yields of 82% and 88%, respectively. When used as the emitting layer in non-doped devices, TPO-AP outperformed AP-TPO, achieving a current efficiency of 5.49 cd/A and an external quantum efficiency of 4.26% in electroluminescence. These materials introduce a new category of deep blue emitters in the organic light-emitting diodes field, combining characteristics related to the electron transport layer.

Tailoring the Size and Shape of ZnO Nanoparticles for Enhanced Performance of OLED Device.

We synthesized zinc oxide nanoparticles (ZnO NPs) by meticulously controlling both temperature and reaction times, allowing us to fine-tune their crystalline properties, morphology, and particle dimensions. This analysis confirmed the existence of a mixture of rod and sphere shapes (ZnO-I), including rod-shaped NPs with an average size of 14.8 nm × 5.2 nm and spherical NPs with an average diameter of 5.27 nm. We subsequently incorporated these synthesized ZnO NPs into organic light-emitting diode (OLED) devices for red, green, and blue colors, utilizing them as the electron injection layer through a solution-based process. The green OLED device using ZnO-I exhibited a promising current efficiency of 4.02 cd/A and an external quantum efficiency of 1.47%.

Effect of Trap Behavior on the Reliability Instability of Metamorphic Buffer in InAlAs/InGaAs MHEMT on GaAs.

Our investigation focused on assessing the influence of the metamorphic buffer in metamorphic high-electron-mobility transistors (MHEMT) that were grown on GaAs substrates. While an MHEMT exhibited elevated off-state current levels, its direct current (DC) and radio frequency (RF) traits were found to be comparable to those of InP-based lattice-matched high-electron-mobility transistors (LM-HEMTs). However, the Pulsed I-V measurement results confirmed the presence of the fast transient charging effect, leading to a more substantial degradation in drain current observed in MHEMT. In addition, through the low-frequency noise characteristics, it was confirmed that the dominant trapping location was located in the bulk site. The slope of the 1/f noise measurement indicated that the primary trapping site was in proximity to the bulk traps. The carrier-number-fluctuation (CNF) model was employed to extract the bulk trap density (Nt). For the LM-HEMTs, the value was at 3.27 × 1016 eV-1·cm-3, while for the MHEMT, it was 3.56 × 1017 eV-1·cm-3.

Impact of Charge-Trapping Effects on Reliability Instability in AlxGa1-xN/GaN High-Electron-Mobility Transistors with Various Al Compositions.

In this study, we present a detailed analysis of trapping characteristics at the AlxGa1-xN/GaN interface of AlxGa1-xN/GaN high-electron-mobility transistors (HEMTs) with reliability assessments, demonstrating how the composition of the Al in the AlxGa1-xN barrier impacts the performance of the device. Reliability instability assessment in two different AlxGa1-xN/GaN HEMTs [x = 0.25, 0.45] using a single-pulse ID-VD characterization technique revealed higher drain-current degradation (∆ID) with pulse time for Al0.45Ga0.55N/GaN devices which correlates to the fast-transient charge-trapping in the defect sites near the interface of AlxGa1-xN/GaN. Constant voltage stress (CVS) measurement was used to analyze the charge-trapping phenomena of the channel carriers for long-term reliability testing. Al0.45Ga0.55N/GaN devices exhibited higher-threshold voltage shifting (∆VT) caused by stress electric fields, verifying the interfacial deterioration phenomenon. Defect sites near the interface of the AlGaN barrier responded to the stress electric fields and captured channel electrons-resulting in these charging effects that could be partially reversed using recovery voltages. The quantitative extraction of volume trap density (Nt) using 1/f low-frequency noise characterizations unveiled a 40% reduced Nt for the Al0.25Ga0.75N/GaN device, further verifying the higher trapping phenomena in the Al0.45Ga0.55N barrier caused by the rougher Al0.45Ga0.55N/GaN interface.

Explicit Thermal Resistance Model of Self-Heating Effects of AlGaN/GaN HEMTs with Linear and Non-Linear Thermal Conductivity.

We presented an explicit empirical model of the thermal resistance of AlGaN/GaN high-electron-mobility transistors on three distinct substrates, including sapphire, SiC, and Si. This model considered both a linear and non-linear thermal resistance model of AlGaN/GaN HEMT, the thickness of the host substrate layers, and the gate length and width. The non-linear nature of channel temperature-visible at the high-power dissipation stage-along with linear dependency, was constructed within a single equation. Comparisons with the channel temperature measurement procedure (DC) and charge-control-based device modeling were performed to verify the model's validity, and the results were in favorable agreement with the observed model data, with only a 1.5% error rate compared to the measurement data. An agile expression for the channel temperature is also important for designing power devices and monolithic microwave integrated circuits. The suggested approach provides several techniques for investigation that could otherwise be impractical or unattainable when utilizing time-consuming numerical simulations.

Effect of high-pressure D2 and H2 annealing on LFN properties in FD-SOI pTFET.

Tunneling field-effect transistors (TFETs) are a promising candidate for the next generation of low-power devices, but their performance is very sensitive to traps near the tunneling junction. This study investigated the effects of high-pressure deuterium (D2) annealing and hydrogen (H2) annealing on the electrical performance and low-frequency noise (LFN) of a fully depleted silicon-on-insulator p-type TFET. Without high-pressure annealing, the typical noise power spectral density exhibited two Lorentzian spectra that were affected by fast and slow trap sites. With high-pressure annealing, the interface trap density related to fast trap sites was reduced. The passivation of traps near the tunneling junction indicates that high-pressure H2 and D2 annealing improves the electrical performance and LFN properties, and it may become a significant and necessary step for realizing integrated TFET technology in the future.

Novel Yellow Azo Pyridone Derivatives with Different Halide Atoms for Image-Sensor Color Filters.

Novel yellow azo pyridone dye derivatives were synthesized for use in image-sensor color filters. The synthesized compounds have a basic chemical structure composed of azo, hydroxy, amide, and nitrile groups as well as different halide groups. New materials were evaluated on the basis of their optical, thermal, and surface properties under conditions mimicking those of a commercial device fabrication process. A comparison of their related performance revealed that, among the four prepared compounds, 5-((4,6-dichlorocyclohexa-2,4-dien-1-yl)diazenyl)-6-hydroxy-1,4-dimethyl-2-oxo-1,2-dihydropyridine-3-carbonitrile (Cl-PAMOPC) exhibited the best performance as an image-sensor color filter material, including a solubility greater than 0.1 wt% in propylene glycol monomethyl ether acetate solvent, a high decomposition temperature of 263 °C, and stable color difference values of 4.93 and 3.88 after a thermal treatment and a solvent-resistance test, respectively. The results suggest that Cl-PAMOPC can be used as a green dye additive in an image-sensor colorant.

Three-Color White Photoluminescence Emission Using Perovskite Nanoplatelets and Organic Emitter.

Three organic blue-light-emitting tetraphenylethylene (TPE) derivatives that exhibit aggregation-induced emission (AIE) were used as additives in the preparation of inorganic perovskite-structured green-light-emitting materials for three-color white-light emission. For these organic-inorganic light-emitting materials, two-color (blue and green) light-emitting films based on the CsPbBr3 perovskite-structured green-light-emitting inorganic material were prepared. The three TPE derivatives were prepared by varying the number of bromide groups, and a distinct AIE effect was confirmed when the derivatives were dissolved in a water-tetrahydrofuran mixed solvent containing 90 vol% water. When 0.2 molar ratio of the 1,1,2,2-tetrakis(4-bromophenyl)ethylene (TeBrTPE) additive was mixed with nanocrystal-pinning toluene solvent, the green-light-emission photoluminescence quantum efficiency (PLQY) value at 535 nm was 47 times greater than that of the pure bulk CsPbBr3 without additives and a blue emission at 475 nm was observed from the TeBrTPE itself. When a CBP:Ir(piq)3 film was prepared on top of this layer, three PL peaks with maximum wavelength values of 470, 535, and 613 nm were confirmed. The film exhibited white-light emission with CIE color coordinates of (0.25, 0.36).

Zinc oxide and indium-gallium-zinc-oxide bi-layer synaptic device with highly linear long-term potentiation and depression characteristics.

The electrical properties, resistive switching behavior, and long-term potentiation/depression (LTP/LTD) in a single indium-gallium-zinc-oxide (IGZO) and bi-layer IGZO/ZnO (ZnO: zinc oxide) memristors were investigated for synapse application. The use of the oxide bi-layer memristors, in particular, improved electrical properties such as stability, memristor reliability, and an increase in synaptic weight states. The set voltage of bi-layer IGZO/ZnO memristors was 0.9 V, and the reset voltage was around - 0.7 V, resulting in a low-operating voltage for neuromorphic systems. The oxygen vacancies in the X-ray photoelectron spectroscopy analysis played a role in the modulation of the high-resistance state (HRS) (oxygen-deficient) and the low-resistance state (oxygen-rich) region. The VRESET of the bi-layer IGZO/ZnO memristors was lower than that of a single IGZO, which implied that oxygen-vacancy filaments could be easily ruptured due to the higher oxygen vacancy peak HRS layer. The nonlinearity of the LTP and LTD characteristics in a bi-layer IGZO/ZnO memristor was 6.77% and 11.49%, respectively, compared to those of 20.03% and 51.1% in a single IGZO memristor, respectively. Therefore, the extra ZnO layer in the bi-layer memristor with IGZO was potentially significant and essential to achieve a small set voltage and a reset voltage, and the switching behavior to form the conductive path.

New Thermal Latent Catalyst Using Titanium and Organic Ligand for Urethane Polymerization.

New thermal-latent metal catalyst such as tetrakis (lauorate) titanium (LPTi) was designed and synthesized based on a lauroyl peroxide and titanium. The synthetic method is simple with one step reaction. LPTi structure was confirmed by FT-IR analysis, also nano-sized structure of LPTi confirmed using SEM-EDX. LPTi is thermal-latent metal catalyst including titanium that not only promotes urethane synthesis reaction but also increases the dissociation rate of blocked isocyanate. As a result of quantitative analysis of NCO (%) through back titration, when LPTi was added, NCO (%) increased from 2.34% to 3.24%. LPTi can be used as an excellent catalyst for urethane reaction by reducing the polymerization time by about 30% compared to no catalyst. LPTi can be applied to the electronic polymer synthesis.

Synthesis and Blue Pixel Property of New Violet Dye for Image Sensors.

In this study, a blue photoresist with the hybrid dye-pigment system was developed by mixing xanthene-based dye (XPDIA) and blue pigment 15:6 (1:1, 5 wt% of total mixture amount) in order to develop high-performance image sensors with high thermal and chemical stability. The colorant used in this study has the nano-sized particle of around 100 nm and the physical property is related with the photonic property in image sensor application such as the cameras of mobile phone, car black box, security, etc. The hybrid dye-pigment system showed a high transmittance of more than 90% at 450 nm, and Δab showed very low color difference of 0.52. In solvent resistance, high transmittance of 90% was perfectly maintained, and Δab showed low color difference of 1.08. Migration test result exhibited no change at all after dipping in PGMEA transmittance spectrum. These results are due to the high absorption optical properties of XPDIA dye in the HDPS and the high thermal and chemical stability properties of the PB15:6 pigment. As a result, it was confirmed that the mixed blue hybrid spin coating film exhibited excellent thermal and chemical stability as well as good optical property.

High Efficiency Green Fluorescent Dopant Through the Optimized Side Group for Organic Light Emitting Diodes.

OLED light emitting materials have a molecular size corresponding to the nano scale and are converted into light energy when given electrical energy. The new green fluorescent dopant material was successfully synthesized by using anthracene as a central core and introducing a methyl group and tert-butyl group at various positions as diphenylamine group. Two compounds are N9,N9,N10,N10-tetraphenylanthracene-9,10-diamine (TAD) and N9,N10-bis(4-(tert-butyl) phenyl)-N9,N10-di-o-tolylanthracene-9,10-diamine (p-Tb-o-Me-TAD). The synthesized material emits green light with the maximum wavelengths of 508 and 523 nm. p-Tb-o-Me-TAD shows excellent PLQY of 86.2% in solution state. When the synthesized material was used as a dopant in a device, TAD showed current efficiency (CE) of 17.71 cd/A and external quantum efficiency (EQE) of 6.11%. The device using p-Tb-o-Me-TAD dopant exhibited current efficiency (CE) of 24.24 cd/A and external quantum efficiency (EQE) of 7.27%.

Synthesis and Electroluminescence Property of Anthracene Green Fluorescent Derivatives Based on Optimized Side Groups.

Molecular size of OLED emitting materials is nano-metric size and when it is applied to the electric field it emits the light based on the energy conversion result. As new green fluorescent emitters, N,N,N',N'-Tetra-m-tolyl-anthracene-9,10-diamine (m-Me-TAD) and N,N,N',N'-Tetra-p-tolyl-anthracene-9,10-diamine (p-Me-TAD) were synthesized and the properties were evaluated. In solution state, photoluminescence (PL) maximum wavelength is 517 nm for m-Me-TAD and 529 nm for p-Me-TAD. In electroluminescence (EL) spectra, EL maximum wavelength of m-Me-TAD is 518 nm and p-Me-TAD is 533 nm. The doped device using m-Me-TAD as green fluorescent dopant exhibited current efficiency (CE) of 17.41 cd/A and external quantum efficiency (EQE) of 7.41%. The doped device with p-Me-TAD was optimized in order to achieve a green OLED with high efficiency.

Synthesis and Physical Properties of New Blue Color Filter Dye Using on Triarylmethine Moiety for Image Sensors.

In this study, a triarylmethine derivative of DMCEBA-BTSA with the high thermal and chemical stability was newly synthesized in order to develop a high-performance image sensor. It showed a high transmittance of more than 80% at 450 nm and △Eab showed a very low color difference of 2.32 after thermal treatment. In solvent resistance, transmittance of 90% was not changed and △Eab showed a low color difference of 0.67 before and after solvent dipping. As a results of the migration test, there was no change at all after dipping in the PGMEA transmittance spectrum. It was confirmed that the newly synthesized blue colorant exhibited excellent thermal and chemical stability and it could be applied to image sensor color filter application as the blue color.