ACS Applied Electronic Materials最新文献

Gallium nitride-based nano/microscale light-emitting diodes operating under alternating-current single-contact driving have garnered significant attention due to their unique device characteristics and potential applications in device-level encryption, mimicking biological afferent nerves and self-emissive displays. In this work, we investigate the influence of quantum well periods on the performance of single-contact GaN blue micro-LEDs under AC driving, where the anode is directly formed on the p-type GaN and the cathode is formed on the backside of the sapphire substrate. Under AC driving, devices with fewer quantum well periods exhibit higher peak currents and stronger electroluminescence. In particular, the device with three quantum wells shows a reduced working voltage of 16.3 V, which is 29.4% lower than that of the device with nine quantum wells. These results demonstrate single-contact micro-LEDs with fewer quantum well pairs had higher efficiencies under AC driving. Finite-element modeling further shows that reducing the number of quantum well periods increases the hole concentration within the wells during the forward half-cycle of AC driving, a consequence of the larger equivalent capacitance that strengthens current injection under AC excitation.

Phase-pure orthorhombic vanadium pentoxide (V₂O₅) nanostructures synthesized via a solvothermal method are systematically evaluated for their dual functionality in electrochemical energy storage and electrocatalytic water-splitting applications. Electrochemical investigations in three aqueous electrolytes reveal superior supercapacitor performance in alkaline 6 M KOH, achieving the highest areal capacitance of 31 mF cm^–2 at 5 mV s^–1, energy density of 0.86 μWh cm^–2, and power density of 0.8 mW cm^–2. The supercapacitor further demonstrates outstanding long-term stability, preserving 95% of its initial capacitance after 10,000 charge–discharge cycles. In addition, the electrochemical performance of the supercapacitor is investigated in acidic H₂SO₄ electrolyte and neutral Na₂SO₄ electrolyte. For water-splitting applications in 1 M KOH, V₂O₅ exhibits promising bifunctional electrocatalytic activity with low overpotentials of 177 mV for the hydrogen evolution reaction and 478 mV for the oxygen evolution reaction at 10 mA cm^–2, with a high electrochemically active surface area of 51 cm² facilitating abundant active sites for catalytic reactions. These findings demonstrate that V₂O₅ nanostructures represent versatile materials for sustainable energy applications, offering dual functionality as high-performance supercapacitor electrodes and efficient water-splitting electrocatalysts.

This study presents a high-performance nickel–cobalt sulfide–terephthalic acid (NCS–BDC) composite electrode synthesized via a simple solvothermal route for advanced supercapacitor applications. The integration of the BDC organic linker promotes a highly mesoporous architecture and creates abundant active sites, compensating for the material’s moderate surface area. The resulting NCS–BDC electrode exhibits exceptional electrochemical properties, delivering a high specific capacitance of 1698.87 F g^–1 at 0.5 A g^–1 in a 2 M KOH electrolyte. When configured into an asymmetric supercapacitor (ASC) using activated carbon, the device achieves a maximum energy density of 52.29 Wh kg^–1 and demonstrates outstanding stability, retaining 92% of its initial capacitance after 5000 cycles. Ex-situ XRD confirms that the intrinsic structural integrity of the cubic spinel phase is perfectly preserved postcycling. These findings establish NCS–BDC as a robust and promising electrode material for next-generation energy storage.

Phthalocyanines (Pcs), metal phthalocyanines (MPcs), and their supramolecular assemblies have emerged as pivotal materials in molecular electronics due to their exceptional chemical robustness, electronic tunability, and structural versatility. Despite the inherent insolubility of unsubstituted Pcs, the incorporation of different metal ions into the central cavity of the macrocyclic core significantly improves the solubility, processability, and charge transport characteristics. Various MPcs exhibit remarkable electrical conductivity, chemical stability, and semiconducting behavior, rendering them highly suitable for integration into organic field-effect transistors (OFETs) and flexible electronic systems. Their capability to function as n-, p-, or ambipolar semiconductors further enhances their utility in diverse optoelectronic applications. This review records the historical milestones and contemporary progress in MPc-based OFETs, tracing the discovery of phthalocyanines starting from 1907 and CuPc synthesis in 1927, and focusing on OFET adoption from the 1980s onward. We analyze their structural, optical, and electronic properties as well as fundamental OFET operation principles, including device architecture and charge transport mechanisms. Emphasis is placed on interface engineering, especially via self-assembled monolayers (SAMs), which modulate interfacial dipoles to optimize the charge injection, carrier density, and threshold voltage. Surface treatments and dielectric layer design critically influence molecular orientation, grain size, and trap density, thereby enhancing the mobility and device stability. Importantly, the review emphasizes the practical significance of MPcs in enabling cost-effective, flexible, and stable OFETs, thereby providing a valuable insight for researchers and engineers aiming to realize next-generation organic electronics leveraging MPc materials.

The structural flexibility of BiVO₄-based ceramics enables diverse electrical functionalities, ranging from oxide ion conductivity to promising dielectric performance. This study investigated the structural evolution, electrical transport, and dielectric behavior of Bi_1–xLa_xVO₄ (0 ≤ x ≤ 1) ceramics, in which Bi³⁺ is progressively substituted by La³⁺. Using variable-temperature X–ray diffraction (VT–XRD) and neutron powder diffraction (NPD), the phase transitions and crystallographic parameters were systematically analyzed. La³⁺ substitution induces a structural transformation from monoclinic fergusonite-type BiVO₄ to tetragonal zircon-type BiVO₄ and, ultimately, to a monoclinic monazite-type LaVO₄ phase. Impedance spectroscopy and EMF measurements reveal that electronic conduction dominates across the series, with Bi_0.8La_0.2VO₄ exhibiting the highest conductivity of 2 × 10^–3 S cm^–1 in air at 700 °C. Dielectric characterization shows that La³⁺ incorporation slightly improves thermal stability, with the temperature coefficient of resonant frequency (TCF) in Bi_0.9La_0.1VO₄ improving from −280 to −156 ppm/°C. In addition, it features a dielectric constant of 52 and a quality factor of 4360 GHz. These findings provide comprehensive insight into the structure–property relationships in La-substituted BiVO₄ ceramics and demonstrate their potential for applications in electronic and energy-related devices.

The magnetic proximity effect (MPE) enables nonmagnetic layers to acquire the induced magnetism through interfacial coupling with adjacent ferromagnetic layers. Self-intercalated Cr_1+δTe₂ films are ideal materials for forming magnetic heterostructures. However, the MPE and the interfacial exchange coupling in Cr_1+δTe₂-based heterostructures remain underexplored. Here, we observe a large anomalous Hall effect (203 nΩ cm at 15 K) in Cr₅Te₆/Pt heterostructures, representing the maximum value reported in magnetic insulator/heavy metal heterostructures so far. X-ray magnetic circular dichroism and X-ray resonant magnetic scattering measurements clearly confirm MPE-induced magnetic moments in the Pt thin layer. An antiferromagnetic exchange coupling is revealed, and first-principles calculations further clarify the underlying microscopic mechanism.

To modulate the optical and electrical properties of quasi-intrinsic CsPbBr₃ epitaxial films, europium bromide (EuBr₃) is introduced as a heterovalent dopant source, and europium-doped CsPbBr₃ (CsPbBr₃:Eu) films are epitaxially grown on (100)-oriented SrTiO₃ substrates via pulsed laser deposition (PLD). By X-ray diffraction (XRD), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS) analyses, we demonstrate that Eu³⁺ ions incorporate into the lattices of CsPbBr₃ epitaxial films and partially substitute for B-site Pb²⁺. Temperature-dependent photoluminescence (TDPL) studies reveal the optical signatures of Eu-induced donor defects in the CsPbBr₃:Eu films, with a donor-bound exciton (D⁰X) emission peak being clearly identified. Ultraviolet photoelectron spectroscopy (UPS) and Hall results demonstrate that the conductive type of epitaxial films changes from quasi-intrinsic to obvious N-type after Eu³⁺ doping. Moreover, Eu³⁺doping also remarkably reduced the trap density and enhanced the film conductivity. As a result, the CsPbBr₃:Eu film photodetector achieves a responsivity nearly five times that of its undoped device, along with an increase in detectivity from 8.91 × 10¹² to 4.17 × 10¹³ Jones. The epitaxial film photodetectors without encapsulation show good long-term stability in ambient air. Our work demonstrates that heterovalent doping is a viable strategy for modulating the semiconductor properties of CsPbBr₃ epitaxial films, offering a valuable idea for designing high-performance photoelectric devices.

Ta₂O₅/Al₂O₃ analog memristive devices are promising candidates for next-generation neuromorphic computing applications. This study presents a comprehensive investigation of the charge transport mechanisms in Ta₂O₅/Al₂O₃ devices, with a focus on identifying the properties and location of the defects involved in the formation of the conductive filament and analog resistive switching. By integrating experimental measurements with multiphonon charge transport simulations, we show that the relative thickness of the Ta₂O₅ and Al₂O₃ layers plays a pivotal role in determining the properties and location of the dominant defects that control the conduction through the RRAM stack. These defects are generated during the formation of the conductive filament and are, therefore, involved in the switching behavior. Sensitivity maps are utilized to pinpoint both the energy levels and spatial positions of defects within the oxide layers that contribute to the switching current. Temperature-dependent current–voltage (I–V) measurements allow us to extract key trap properties, including thermal ionization and relaxation energies, which are used to identify defects in the individual dielectric layers that contribute to the resistive switching. These insights offer valuable guidance for optimizing both the design and performance of these devices for neuromorphic applications.

Development of dopant-free HTMs is important for boosting the performance and durability of perovskite solar cells. Here, we report the design and synthesis of benzodithiophene-thiadiazole quinoxaline polymers (P1–P3) with OCH₃, CH₃, and CF₃ substitutions, and are characterized by using GPC and XRD analysis. Further, we systematically investigated their hole mobility and its impact on the efficiency of perovskite solar cells. The presence of S··· O interactions provided backbone rigidity, promoting tighter molecular packing and enhancing charge transport properties. Density functional theory calculations, in conjunction with XRD analysis, revealed the presence of favorable noncovalent S···O contacts in P1, confirming the role of intramolecular interactions in enhancing backbone planarity and packing order. Additionally, alkyl side chains were strategically incorporated to increase solubility while maintaining planarity, resulting in an optimized HOMO energy level of approximately −5.25 eV. Among the synthesized polymers, the OCH₃-substituted derivative exhibited the maximum power conversion efficiency (PCE) of 13.77%, significantly outperforming traditional dopant-free Spiro-OMeTAD-based systems. The strong π–π* interactions between the lone pair of electrons on the OCH₃ group and sulfur atoms in the polymer backbone facilitate superior charge extraction and molecular packing, resulting in improved hole transport and prolonged operational stability under normal environmental conditions. These findings highlight the potential of rational molecular engineering in advancing dopant-free HTMs for next-generation perovskite photovoltaics.

The interfacial electric field (IEF) in semiconductor heterojunctions plays a vital role in self-powered photodetection. However, effectively modulating the IEF to enhance broadband photodetection in single heterojunctions remains a significant challenge. In this study, we present a strategy for IEF-modulated broadband self-powered photodetection using a plasmonic W₁₈O₄₉/TiO₂ heterojunction film. The film is fabricated through the solvothermal growth of W₁₈O₄₉ nanowires on TiO₂ nanorod arrays. By applying external voltage treatment, we demonstrate the ability to tune the Fermi level of the plasmonic W₁₈O₄₉ component, which in turn modulates the IEF at the W₁₈O₄₉/TiO₂ heterojunction. The enhanced IEF facilitates both the separation of interband-excited electron–hole pairs and the ultrafast transfer of IR-excited plasmonic hot electrons. Notably, compared with 0 V and −2 V treatments, the +2 V-treated heterojunction film exhibits a remarkable ∼2.9-fold and ∼4.5-fold enhancement in 365 nm responsivity (598.6 μA/W), respectively. Additionally, the 0 V-treated film shows a ∼3.2-fold higher 940 nm responsivity than the −2 V-treated counterpart. In contrast, single-component films exhibit negligible responses, confirming the essential role of the IEF in enabling self-powered UV-to-NIR broadband photodetection. This work offers a promising approach for achieving high-performance optoelectronics by modulating the IEF in semiconductor heterojunctions.