Controlling oxygen vacancies in metal oxide thin films is critical for enhancing charge transport and interfacial stability in polymer photodetectors (PPDs). Ultraviolet (UV) ozone treatment is an effective approach for modulating oxygen vacancies. We investigated the effects of UV ozone treatment on aluminum-doped zinc oxide (AZO) and the performance of PPDs incorporating these films. At -2 V, treatment times of 10 and 20 min reduced the dark current density from 2.46 & times; 10-4 A/cm2 (untreated) to 4.24 & times; 10-5 and 6.05 & times; 10-5 A/cm2, corresponding to 5.8-fold and 4.0-fold reductions, respectively, and increased the specific detectivity (Dshot*) at 700 nm from 4.68 & times; 1010 to 1.12 & times; 1011 Jones. These treatment times also increased the fill factor to 61.5% and 60.5%, respectively, compared to 56.9% for untreated devices. Optical and electrical analyses revealed that increasing treatment time reduced the optical bandgap, increased interfacial barrier resistance, reduced bulk capacitance, and improved surface morphology. X-ray photoelectron spectroscopy confirmed decreased oxygen vacancies and enhanced metal-oxygen bonding. However, treatment beyond 30 min induced surface degradation and excessive resistivity, limiting device performance. These results demonstrate that UV ozone treatment offers a simple yet effective route to engineering metal oxide interfaces and achieving high-performance PPDs.

In this study, we fabricated coplanar capacitive touch sensors using electrohydrodynamic (EHD) printing and systematically investigated the influence of electrode width, spacing, height, and roughness on sensing performance. Reducing electrode spacing enhanced electrostatic coupling, improving both capacitance change (Delta C) and signal-to-noise ratio (SNR). Electrode width exhibited an optimal value, beyond which increased baseline capacitance reduced sensitivity. Although Delta C increased with electrode height, SNR decreased at higher thickness due to morphology-induced noise amplification caused by multi-pass printing. Ultrathin (similar to 60 nm) electrodes with high morphological uniformity achieved a maximum SNR of 41.6 dB with optical transmittance exceeding 93%. These results reveal that capacitive sensing performance is governed not only by geometric scaling but also by morphology-controlled noise, providing practical design guidelines for transparent, high-performance touch sensors.

Inkjet printing offers a scalable and material-efficient route for fabricating high-resolution optoelectronic devices, yet the strong viscoelasticity of high-molecular-weight conjugated polymers remains a critical bottleneck for reliable jetting. Here, we introduce ultrasound-mediated polymer processing as a strategy to tune the viscoelasticity of a light-emitting polymeric material without external additives. Sonochemical treatment of Super Yellow selectively cleaved alkoxy side chains, as revealed by 1H NMR and gel permeation chromatography, reducing molecular weight and entanglement density while preserving the π-conjugated backbone and its optical functionality. High-frequency rheological characterization using a piezo-axial vibrator confirmed that the treated inks exhibit markedly reduced elasticity and complex viscosity, enabling stable droplet formation under conditions that were previously unprintable. Leveraging this rheological control, we achieved precise pixel definition and uniform emissive layers in inkjet-printed OLEDs, which delivered a maximum external quantum efficiency of 4.55%, surpassing that of spin-coated references. This study establishes ultrasound-assisted rheological tuning as a generalizable approach to overcome viscoelastic constraints in polymer inks, opening new opportunities for high-resolution printed organic light-emitting diode displays and other solution-processed electronic devices.

Abstract Quantum dot light-emitting diodes (QLEDs) have attracted considerable attention as next-generation light-emitting devices capable of achieving high emission efficiency based on their organic–inorganic hybrid architecture. However, the environmental degradation and performance loss arising from the vulnerability of the organic layers within the device to oxygen and moisture remain a major factor limiting long-term device stability. To address this issue, we introduce VNPB (N4,N4′-di(naphthalen-1-yl)-N4,N4′-bis(4-vinylphenyl)biphenyl-4,4′-diamine), a cross-linkable hole transport layer (HTL) material, into InP-based QLEDs and systematically investigate the effect of the cross-linking density, controlled by the post-annealing temperature, on the electrical and optical properties of the devices. VNPB contains terminal vinyl groups that enable the formation of an intermolecular covalent network during thermal annealing, thereby providing excellent solvent resistance and structural stability that suppress the re-dissolution of the underlying layer during multilayer solution processing. By varying the post-annealing temperature of the VNPB film from 160 to 190 °C, we elucidated the effect of the cross-linking density on the performance of InP-based QLEDs. Rinsing tests confirmed that the cross-linking density increased progressively with annealing temperature, forming a robust network. Device analysis showed that the 170 °C condition achieved a maximum EQE of 5.55% and the optimal operational lifetime (T70 = 45.1 h). In contrast, devices annealed at 180–190 °C exhibited increased surface roughness and local current response. Together with the larger voltage variation observed under constant-current operation, these results suggest increased morphology-induced localized conduction and electrical instability, resulting in non-uniform charge transport and charge imbalance. This study demonstrates that controlling the cross-linking density of the hole transport layer can serve as an important processing strategy for regulating charge injection balance and recombination behavior in solution-processed QLEDs.

Inverted organic photodetectors (OPDs) have attracted significant attention due to their facilitated interfacial optimization at the bottom electrode and compatibility with diverse solution processes. However, high dark current originating from the electron transport layer (ETL) remains a major factor limiting device performance. In particular, interfacial defects and leakage currents in ITO/ZnO-based inverted OPDs lead to degradation of detectivity ( D shot * ) and signal-to-noise ratio (SNR). In this study, inverted OPDs incorporating an octadecylphosphonic acid (ODPA) self-assembled monolayer (SAM) on an indium tin oxide (ITO) electrode were fabricated, and the effects of interfacial modulation were systematically investigated. The device architecture consisted of ITO/ODPA/ZnO nanoparticles (NPs)/P3HT:PCBM/MoO3/Ag. Compared to reference devices without SAM treatment, the ODPA-modified OPDs exhibited a reduction in dark current by a factor of approximately 13, decreasing from 8.55 × 10-4 to 6.36 × 10-5 A cm-2 at -2 V, while maintaining stable photoresponse characteristics. This pronounced suppression of dark current is attributed to effective modulation of the electronic properties at the ITO/ZnO interface by the ODPA SAM, which suppresses interfacial leakage pathways. These results demonstrate that phosphonic acid-based SAMs provide an effective interfacial engineering strategy for achieving low-noise characteristics in inverted OPDs and offer a viable approach for the design of high-performance organic photodetectors.

Real-time monitoring of drying dynamics is critical for ensuring high-quality thin-film fabrication in inkjet printing. Here, we present a classification framework for the drying stages of ZnO nanoparticle inks on 200-PPI patterned substrates using low-resolution optical images. By correlating 3D surface profiles with visual textures, we show how the volatility mismatch and viscosity contrast of binary solvents govern hydrodynamic evolution, generating distinct image textures for each stage. Based on this, we define three drying stages for binary mixed-solvent inks and two for single-solvent systems. A lightweight convolutional neural network, trained on grayscale images downsampled to 115 × 40 pixels, achieved a 99.4% test accuracy. Explainable AI analyses, utilizing input gradient saliency and gradient-weighted class activation mapping (Grad-CAM), revealed that the model autonomously learns to focus on the central pixel region-where physical variations are most pronounced-without any spatial supervision. Furthermore, the lightweight model requires only 0.64 ms per image for inference on a GPU, representing a 16.4-fold reduction in theoretical computational cost compared to the baseline. This image-only approach enables reliable, computationally efficient process monitoring, establishing a practical pathway for real-time quality control specifically for the tested ZnO nanoparticle inkjet printing configuration.

Inkjet printing is a key technology for realizing electroluminescent quantum displays owing to its high material utilization efficiency and excellent scalability in patterning processes. Nevertheless, despite continuous advances in quantum dot synthesis and device architecture, QLED devices in which all layers are fabricated exclusively via inkjet printing remain extremely rare. This limitation originates from insufficient process compatibility among functional materials and the narrow solvent selection window required to achieve uniform thin-film formation. Herein, these challenges are addressed by introducing an intense pulsed light (IPL) process as an alternative to conventional thermal annealing, enabling the use of materials that require high-temperature treatment without damaging the pattern definition layer. Furthermore, the physicochemical properties of solvents were systematically analyzed to optimize processing conditions for uniform thin-film formation via inkjet printing. Consequently, compared with PEDOT:PSS-based devices, which exhibit limited control over thin-film morphology, devices employing IPL-treated MoOX achieved an approximately sixfold enhancement in external quantum efficiency (EQE) while successfully realizing a pixelated, fully inkjet-printed QLED device with a resolution of 200 ppi. These results demonstrate that the proposed approach effectively expands the material selection window for inkjet-printed QLED displays and presents a promising processing strategy for next-generation printed display applications.

Interfacial trap states and charge-transport imbalance at oxide ETL/quantum-dot interfaces remain key limitations in InP-based QLEDs. Here, we propose a dual-modulation strategy that combines ethanolamine (EA) ligand engineering with Mg-doped ZnO (ZnMgO, ZMO) to simultaneously improve the oxide/QD interface and regulate electron transport. EA ligand attachment on ZnO nanoparticles is first confirmed, and its interfacial benefits are identified: XPS O 1s analysis reveals a reduction in oxygen-vacancy-related surface states, while AFM and KPFM measurements show reduced surface roughness and a lowered surface work function, indicating improved film uniformity and interfacial passivation. However, electron-only SCLC analysis reveals that EA treatment also increases the effective electron mobility of ZnO, which can aggravate electron-dominant charge imbalance despite its beneficial passivation effect. To overcome this trade-off, Mg doping is introduced as a transport-modulation route to intentionally suppress excessive electron transport while retaining the interfacial advantages of EA ligands. By systematically tuning the Mg content in EA-ZMO, electron-only current is progressively reduced, confirming controllable moderation of electron transport. Consequently, EA ligand engineering passivates interfacial defects and facilitates electron injection, whereas Mg-content control compensates for the EA-induced mobility enhancement and restores charge balance. The optimized 12.5% EA-ZMO ETL achieves the most balanced charge injection, yielding a peak EQE of 9.23% through coordinated defect passivation and mobility modulation.

Reliable thin-film heaters that provide rapid and uniform heating are critical for point-of-care molecular diagnostics. In this work, we present the additive manufacturing of electrothermal thin-film heaters that are directly integrated with an on-chip chamber. This configuration enables isothermal amplification of deoxyribonucleic acid (DNA) in a portable and compact platform. Two additive processes were compared. The first was a five-layer inkjet-printed (5L-I) heater, optimized using a 10 min oxygen plasma treatment and a 40 degrees C substrate (0.5 % uncoverage at five layers). The second was a single-layer direct ink writing (DIW) printed heater (1L-D) with conformal coverage. Infrared (IR) thermography showed quadratic voltage-temperature scaling for both heaters. The 1L-D heater achieved similar to 1.7 times higher maximum temperature and faster heating/cooling rates, consistent with lower resistance and higher conductivity. Long-duration thermal assessments confirmed that the 1L-D heaters sustained stable temperatures over 60 min (79.5-81.9 degrees C at 3 V; CV < 1 %), demonstrating high reproducibility and reliable performance for continuous isothermal operation. Under water-filled chamber conditions, the 1L-D heater maintained uniform in-plane temperatures (59.3-62.5 degrees C at 3 V; CV < 1.02 %), outperforming the 5L-I heater (CV approximate to 3 %). Parallel Loop-mediated isothermal amplifications (LAMP) at 65 degrees C for 30 min were performed using both the on-chip chamber and a benchtop thermocycler. These tests produced comparable colorimetric and gel electrophoresis results for the target plasmid DNA, pNL1.2, with little amplification observed for the non-target control plasmid, pPZP-RCS2. Overall, the DIW heater provides rapid, uniform, and stable heating suitable for reliable point-of-care isothermal amplification.

Herein, a dual-interface engineering strategy that introduces polyvinylpyrrolidone (PVP) interlayers at the upper and lower interfaces of the indium phosphide (InP) quantum dot (QD) emissive layer is proposed. This strategy aims to address the critical challenges of emissive layer dissolution and charge injection imbalance in all-solution-processed inverted quantum dot light-emitting diodes (QDLEDs). The PVP interlayer at the interface with the QD/hole transport layer effectively suppresses QD dissolution during subsequent solution processing, forming a stable and homogeneous emissive layer. The underlying PVP layer at the electron transport layer/QD interface modulates the electron-hole injection balance and reduces leakage current pathways. The influence of the PVP interlayers on charge transport characteristics and surface morphology was systematically investigated via single-carrier device analysis and atomic force microscopy measurements. The incorporation of PVP interlayers considerably improves the device performance, increasing the external quantum efficiency, current efficiency, and power efficiency by ∼40%, 39%, and 63%, respectively. These findings indicate that PVP-based interface control can effectively enhance the structural stability and electrical performance of inverted InP light-emitting diodes.

Measuring sheet resistance in metal nanowire films without causing damage is critical for advancing transparent conducting electrode technologies, particularly in emerging applications like flexible electronics, displays, and solar cells. Traditional measurement techniques such as four-point probe and Van der Pauw methods often compromise sample integrity and struggle with accurately capturing the electrical homogeneity of nanowire networks. The non-uniform distribution of nanowires significantly impacts electrical performance, with variations in wire density and junction connectivity leading to inconsistent conductivity and potential device failure. This research paper presents a deep learning technique combining Fast Fourier Transform (FFT)-derived and color metric features to predict the sheet resistance of silver nanowire networks. The inputs for the convolutional neural network (CNN) consist of raw high-resolution optical microscopy images, Fast Fourier Transforms of those images, average color representations, and a combination of all three data types, each processed separately. The combination of image, FFT, and average color data yields the best performance. The predictive capacity of the model extends to assessing non-uniformity in nanowire distribution, a crucial parameter for electronic applications. Thus, the integration of image-derived features provides a powerful tool for material property prediction, enhancing quality control, and advancing materials informatics within nanotechnology and device engineering.

Solution processed organic light emitting diodes (s-OLEDs) are promising for low cost, large area, and flexible displays, yet their external quantum efficiencies (EQEs) and operational lifetimes still lag far behind those of vacuum deposited devices owing to inefficient hole transport, interfacial intermixing, and poorly controlled dopant aggregation in the emissive layer. Here, we identify the molecular weight of the polymeric hole transport layer (HTL) as a powerful design parameter for simultaneously tuning dopant aggregation, interfacial intermixing, and carrier transport in green phosphorescent s-OLEDs. Three poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB) HTLs with number-average molecular weights of 51k, 60k, and 130k were incorporated into Ir(mppy)3:CBP green emissive-layer devices and systematically investigated using atomic force microscopy, UV-visible absorption, electroluminescence, and J-V-luminance measurements. We show that the dopant aggregation state is not an undesirable byproduct of solution processing but a critical variable that must be optimized: complete suppression of aggregation by the highly solvent-resistant TFB_130k leads to a low maximum EQE (∼4.1%), severe EQE roll-off, strong parasitic TFB emission, and a shortened lifetime (∼5 h), whereas a moderate level of dopant-dopant interaction and aggregation realized with TFB_51k yields a maximum EQE of ∼9.9% with negligible roll-off at 1000 cd m-2 and an extended lifetime of ∼36 h. These trends arise from molecular weight dependent interfacial intermixing at the TFB/CBP boundary: the relatively low solvent resistance of TFB_51k forms a graded intermixed junction that smooths hole injection and confines the recombination zone within the Ir(mppy)3:CBP bulk, while the sharp interface of TFB_130k drives hole accumulation and interfacial recombination on TFB. Our results establish that engineering an optimal dopant aggregation window and controlled interfacial intermixing via HTL molecular weight design is essential for achieving high efficiency and reliable solution processed green OLEDs.

We developed an inverted OPD by doping the hole-blocking layer with metals, reducing leakage current and enhancing detection performance under reverse bias. IGZO-doped devices exhibited the best leakage current suppression and specific detectivity. Inkjet printing was applied to achieve precise pixelation of the OPD layers, highlighting its potential for largearea, solution-processed Sensor-in-Pixel displays. This work demonstrates the feasibility of OPD fabrication for wearable and security applications.

Organic photodetectors (OPDs) offer advantages such as flexibility, being light in weight, and cost-effectiveness relative to their silicon-based counterparts. However, challenges like high leakage current, slow response time, and low stability limit their performance. In this study, we propose the utilization of sol-gel synthesized indium gallium zinc oxide (IGZO) doped with different metal ratios as a hole-blocking layer to suppress carrier collection and reduce leakage current. We further investigate its impact on OPD performance. Our results demonstrate that the IGZO layer reduced the leakage current by approximately 265-fold relative to the undoped zinc oxide (ZnO) at -2 V and mitigated the degradation of the detectivity (D*) under reverse bias. Impedance analysis further confirmed that the variation in the leakage current under reverse bias correlates with changes in the resistance components due to the doping ratios, and that the increased metal doping of IGZO not only reduces the leakage current but also enhances the conductivity of the individual thin films. These findings indicate that sol-gel-processed IGZO could be applied to various solution-processed devices other than OPD applications.

Indium phosphide (InP) quantum dots (QDs) have emerged as promising candidates for next‐generation display and solid‐state lighting technologies. However, InP‐based quantum dot light‐emitting diodes (QLEDs) using zinc oxide nanoparticles (ZnO NPs) as the electron transport layer (ETL) suffer from performance degradation due to unbalanced carrier injection. This is mainly caused by the high electron mobility of ZnO, which leads to excessive electron injection into the emissive layer. In this study, Poly(4‐vinylpyridine) (PVPy) is introduced as an electron‐blocking interlayer between the ZnO ETL and the InP‐QD emissive layer to mitigate this imbalance. The insulating nature of PVPy effectively limits electron injection, reducing charge accumulation and enhancing device performance. To further evaluate the role of hole transport layers (HTLs) in conjunction with PVPy, devices incorporating solution‐processed HTLs such as TFB (in p‐xylene), PTAA (in chlorobenzene), and a PTAA–PVK blend are fabricated. A thermally evaporated MoO₃ layer is used as the hole injection layer with Ag as the anode. Devices incorporating the PVPy interlayer consistently outperform those without, confirming the interlayer's role in improving charge balance and overall QLED performance. This strategy provides valuable insight into interface engineering for high‐performance, cadmium‐free QLEDs.

Organic/quantum dot light-emitting diode displays have recently been manufactured using inkjet printers, which require stable ink drops and strict control during the printing process. Combining Ansys Fluent and Ansys Mechanical simulations, this research establishes the conditions that stabilize the ink droplets. The feasibility of this approach is verified through a jetting simulation of Newtonian fluids with almost constant viscosity and a comparison of the simulation and experimental results. Then, a commercial non-Newtonian ink with a shear-rate-dependent viscosity is simulated, and the simulation and experimental results are again compared. The study then evaluates why the experimental and simulation outcomes of non-Newtonian fluids differ under the same voltage conditions. Besides finding the stable drop conditions, the performed inkjet simulations reveal the pressure changes in the inkjet nozzle.

This study explores the influence of nitrogen gas flow rate on the electrical characteristics of indium-gallium-zinc-oxide (IGZO) thin-film transistors (TFTs) annealed under heat-assisted UV illumination.The aim is to understand how nitrogen flow rates impact the performance of solution-processed IGZO TFTs annealed at low temperatures, which is crucial for developing highperformance devices for next-generation electronics and temperature-sensitive applications. The IGZO TFTs were fabricated on glass substrates using a bottom-gate top-contact configuration, with the IGZO thin film deposited by inkjet printing and annealed in a chamber with varying nitrogen gas flow rates (0.5, 1, 2, and 5 L/min) at 250 degrees C for 2 hours under UV illumination. The electrical characteristics were extracted from transfer characteristics measurements. The results show that a nitrogen flow rate of 1 L/min enhances the electrical properties of IGZOTFTs, likely due to a suitable concentration of oxygen vacancies. Excessive N2 flow rates (>1 L/min) negatively impact on theTFT characteristics, while lower flow rates (<1 L/min) result in more negative threshold voltages and lower on/off current ratios. The study concludes that optimizing the nitrogen gas flow rate is critical for achieving desired TFT properties, offering a valuable tool for fine-tuning IGZOTFTs to meet specific application requirements.

Organic photodetectors (OPDs) are promising candidates for next-generation optoelectronic devices due to their flexibility, low cost, and scalability. Enhancing OPD performance requires optimizing key layers such as the electron transport layer (ETL) using low-temperature processes to prevent thermal degradation. This study explores the use of low-temperature electron beam annealing (EBA) to improve the performance of Al-doped ZnO (AZO)-based ETLs. The impact of EBA irradiation time (1-8 min) on the structural, morphological, and electrical properties of AZO films was systematically analyzed. EBA effectively modulated oxygen vacancies and reduced surface roughness, lowering trap density and leakage current while enhancing charge transport. An OPD with an ETL treated by 8 min of EBA exhibited superior detectivity (2.22 x 1013 Jones at 0 V) and significantly reduced leakage current compared to a device with conventionally annealed ETLs. Importantly, the low-temperature EBA process preserved the amorphous state of AZO, making it suitable for heat-sensitive and flexible substrates. These findings demonstrate that EBA is a powerful, scalable method for ETL optimization in OPDs and offers a pathway toward high-performance, energy-efficient, and flexible optoelectronic devices.

Various metal-doped titanium dioxide (TiO2) materials have emerged as promising electron transport layers (ETLs) for enhancing the performance of inverted organic photovoltaic (OPV) devices. Among these, zinc (Zn) stands out as a particularly effective dopant for TiO2. Incorporating zinc into TiO2 can enhance its electrical conductivity, energy level alignment, and interfacial charge transport properties, effectively addressing the inherent limitations of pristine TiO2. So, in this study, inverted OPV devices were fabricated using benzodithiophene (PTB7) blended with [6,6]-phenyl-C71-butyric acid methyl ester (PC70BM) as the active layer. The power conversion efficiency (PCE) of devices using Zn-doped TiO2 as the ETL was 7.87 %, which was similar to 16 % higher than the 6.79 % obtained with undoped TiO2. At the Zn-doped TiO2/active layer interface, this improvement is ascribed to decreased trap states, enhanced electron mobility, and inhibited charge recombination. Moreover, Zn doping facilitated superior energy level alignment, enabling more efficient charge extraction. These results demonstrate Zn-doped TiO2's potential as a viable ETL for highly effective inverted OPVs. The study also emphasizes how crucial material doping techniques are to maximizing ETL characteristics and promoting the creation of reasonably priced organic solar cells.

Inkjet printing of electroluminescent quantum dots (EL-QDs) is a promising approach for fabricating the next generation of full-color display panels. However, commercialization and practical application are hindered by the low efficiency and short operational lifetime of the EL-QDs, primarily attributed to solvent-related issues for the inkjet printing process. Here, a mixed-solvent system with a high boiling point is presented to enhance the EL-QD performance by improving film uniformity and suppressing the coffee-ring effect. Combining solvents D1 with T1 increases the viscosity and boiling point, allowing precise evaporation control and reducing drying inconsistencies across large-area substrates. This system facilitates better droplet spreading and pattern fidelity, resulting in enhanced pixel uniformity. In experiments, EL-QDs fabricated with the mixed-solvent system exhibited significantly enhanced device performance compared to those fabricated with a single-solvent system. CdSe-based EL-QDs achieved a 403.8% increase in luminance and a 313.2% improvement in operational lifetime, demonstrating improved stability and brightness. Furthermore, InP-based EL-QDs exhibited a 453.8% increase in luminance and a 238.4% improvement in external quantum efficiency (EQE), validating the mixed-solvent approach in improving efficiency. These findings emphasize the benefits of mixed-solvent systems in achieving high-quality EL-QD deposition via inkjet printing, offering a promising strategy for next-generation display applications.