ACS Applied Electronic Materials最新文献

The ferroelectric field-effect transistor (FeFET), which has nonvolatility, is a key basic element of a logic circuit. In recent years, there has been a growing interest in applying FeFET memory devices in the field of optoelectronics to achieve integrated devices with photon sensing and storage functionalities. However, in the limited development of these compact and versatile optoelectronic memories, the design of an optical absorption layer is still elusive. Wavelength selective optoelectronic memories cannot be realized only using a simple FeFET structure with a 2D channel, especially in the infrared communication band. In this study, we propose a device based on a P(VDF-TrFE)/graphene/SiO₂/p-Si structure, in which the graphene/SiO₂/p-Si architecture has strong infrared absorption capacity due to the interfacial gating effect. The photogenerated carriers can modulate the carrier density in graphene, thereby controlling the polarization effect of P(VDF-TrFE) and achieving nonvolatile storage of optical information. We successfully exhibited six resistive states of optical and electrical signal storage using this device. The programming of the optical and electrical signals can be achieved in this single device simultaneously. This dual-mode multistate storage device that combines light and electricity may become a key component in high-capacity and nonvolatile optical communication hardware.

The fabrication of efficient phototransistors relies on understanding the trapping of photogenerated charge carriers in localized electronic states (known as trap sites) which creates an additional electric field in the active layer. These sites are mostly located at interfaces and impurities within the active layer and play a crucial role in controlling the device performance. Hence, they are crucial considerations in the design of high-responsivity phototransistors. This paper reports on the impact of active-layer interfaces and impurities on the photoresponse behavior of phototransistors based on PTCDI-C₅ (n-type) and C₈-BTBT (p-type) organic semiconductor layers. Trap sites are introduced into various active layers via vacuum evaporation, solution processing, and hybrid processes. The mechanism of charge trapping is elucidated using ultraviolet photoelectron spectroscopy, providing insights into the electron band energy structure at the interfaces. The findings reveal that both interfaces and impurities can significantly affect the photoresponse behavior of the devices. Impurities are found to consistently enhance the photoresponse, whereas interfaces can induce either positive or negative photoresponses, depending on their spatial orientation and bias polarity. This study establishes an important link between the active-layer structure and the photoresponse of devices and provides valuable insights for the design and optimization of high-performance phototransistors.

Seeking to develop more advanced organic photodetectors (OPDs) and organic light-emitting diodes (OLEDs), we designed three derivatives of 2,7-di-tert-butyl-9,9-dimethyl-9,10-dihydroacridine and phenanthroimidazole with either −CF₃ or −C(CH₃)₃ groups. These compounds were synthesized by Buchwald–Hartwig amination reaction with yields of up to 77%. They show high glass transition temperatures above 200 °C and balanced electron and hole transport with mobilities of up to 10^–3 cm²/V·s under strong electric fields. One compound with −C(CH₃)₃ groups outperformed the standard host material in the OLED, which showed 17% higher external quantum efficiency. The low dark current density resulted in enhanced efficiency of OLEDs due to minimal charge leakage. Compared to the commercial material 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), this compound allowed achieving superior photosensitivity in OPDs. The photocurrent to dark current density ratio at a reverse voltage of −10 V was found to be 6000. For TAPC-based OPDs, this ratio was only 43.3. The dark current density was significantly reduced to 4.5 × 10^–7 mA·cm^–2, compared to 3 × 10^–4 mA·cm^–2 for TAPC-based OPDs at the same reverse voltage, thus enhancing the photosensitivity of the OPDs.

There is a high demand for the design of high-performance electrothermal devices, including electrothermal films and actuators, with easy fabrication and low cost. Herein, flexible electrothermal films made of polyimide and carbon nanomaterials and bimorph actuators consisting of polythene and carbon nanomaterials are fabricated by a handwriting technique with a whiteboard marker pen filled with carbon aqueous conductive ink, which is simple and scalable. The electrical performance was examined through lightning diodes by drawing traces on various substrates to form a circuit. In addition, the performance of prepared handwritten devices was compared to that of screen-printed devices, and it was discovered that their performance was similar. The prepared electrothermal films can reach 122 °C with 10 V, and the bimorph actuator exhibits electrical actuation with reversible deformation of 221° under 5 V voltage within 20 s. Furthermore, a cross pattern composed of four pieces of the actuator was fabricated to demonstrate electrically driven actuation. These works provide a simple and fast method to fabricate electrothermal devices for intelligent fields and practical applications.

Transparent flexible resistive sensors have generated significant interest within the rapidly evolving field of stretchable electronics, particularly for applications that require transparency, fatigue resistance, and high sensitivity. Our research proposed a screen-printing strategy to produce transparent flexible resistive sensors characterized by their sensitive responses to droplet variations and endowed with the capability for repeated utilization utilizing silver nanowires (AgNWs) ink and polyethylene terephthalate (PET) substrate. Plasma treatment was implemented to enhance the electrical conductivity of the printed circuit, which can fuse the AgNWs into highly connected frameworks without deteriorating the transmittance properties of the circuit board. Additionally, the cyclic stability in the solution was improved by applying a carbon coating on the AgNWs-based sensors facilitated by the shadow mask. The resistive sensors demonstrate varied current responses when exposed to liquids with differing conductivity levels while maintaining excellent optical performance with an average transmittance of 77.6% at a visible wavelength of 550 nm. The transparent flexible sensors exhibit prospective applications in biomedical sensing, industrial process control, and intelligent packaging for food safety, thereby providing a thought for the next generation of artificial sensors.

Metal oxide nanomaterials possess an exceptional physical and chemical behavior apposite for gas-sensing applications. Among them, titanium dioxide (TiO₂) is a promising, robust, and economical material, and when paired with two-dimensional (2D) materials such as reduced graphene oxide (rGO), the resultant composite system is promoted to an interesting gas-sensing candidate. Properties of rGO- and TiO₂-based nanocomposites depend on the size and shape of TiO₂ nanoparticles and the weight percentage (wt %) ratio of rGO/TiO₂. Herein, the preparation of rGO@bimodal TiO₂ nanocomposites (hereafter referred to as G@TiO₂) by the conventional hydrothermal method having different wt % (1, 2.5, 5, and 10) of rGO with bimodal TiO₂ nanoparticles is reported. Structural, optical, morphological, and microstructural characterizations of the prepared nanocomposites revealed the generation of elongated submicron particles and nanorods of bimodal TiO₂ in the G@TiO₂ samples. The gas sensors based on the prepared materials were fabricated to evaluate their gas-sensing properties. The comparative analysis illustrated that the sensor based on 2.5%G@TiO₂ presented the highest sensitivity and selectivity to n-butanol at room temperature (25 °C). Furthermore, supplemental investigation on n-butanol adsorption properties of all sensors was carried out using a scanning Kelvin probe (SKP) technique, which further corroborated the exceptional n-butanol adsorption (>2 times) for the 2.5%G@TiO₂ surface at room temperature.

In this study, using graphene oxide (GO), glutamine (G), and Cu(II) nanoparticles, a nanocomposite was prepared. Then, the prepared nanocomposite was checked out by various techniques such as X-ray diffraction, Fourier transform infrared, Raman spectrum, scanning electron microscopy, and energy-dispersive X-ray, and the results showed that the desired structure was successfully prepared. Also, a three-electrode system was utilized to measure the electrochemical properties. The specific capacitance of a Cu-doped graphene oxide-glutamine nanocomposite (Cu/G-GO) of 1838 F g^–1 was obtained in a 1 M H₂SO₄ aqueous electrolyte under a current density of 3 A g^–1. Moreover, 85.43% of the initial capacitance of the electrode was preserved after 5000 cycles at 20 A g^–1 (10,000 cycles, 73.12%). Also, the quantum capacitance and the layer distance of GO and G-GO using density functional theory were calculated.

Current overshoot in resistive random access memory (RRAM) can affect the stability and increase the power consumption of devices, which has become a great challenge in RRAM applications. In this study, we analyzed current overshoot in Ti/ZrO₂/Pt devices and proposed a solution to improve device stability through high-temperature forming. The analysis results indicate that current overshoot is likely to occur in the RESET process when the SET voltage is too high, and temperature has an important impact on the conversion voltage of the Ti/ZrO₂/Pt devices. Moreover, we established an electrothermal coupling model of the devices based on the oxygen vacancy conduction mechanism by COMSOL, which could obtain the distribution of the oxygen vacancy concentration in the dielectric layer during resistance conversion at different temperatures and electric fields. Based on the above analysis, by forming at high temperature, the overshoot current is reduced, and the stability of the switching voltage is improved successfully.

Carbazoles with tert-butyl, methoxy, and methoxyethoxy groups are linked with anthracene-based moieties in a series of designed and synthesized compounds with the aim to obtain triplet levels lower than 2 eV and efficient triplet harvesting in electroluminescent devices. The upconversion of triplet excitons is studied theoretically and experimentally. The triplet fusion is responsible for the appearance of blue delayed emission with lifetimes up to 0.15 ms, which is detected for the methoxy-containing compound by photophysical investigation. The tert-butylated emitter shows good performance in organic light emitting diodes (OLEDs), reaching an external quantum efficiency of 5.9% with the 1931 Commission Internationale de l’Éclairage coordinates of (0.14, 0.12). The time-of-flight measurements demonstrate that the derivative of tert-butylcarbazolyl and anthracene is the most promising candidate for electronic devices due to its high hole mobility, reaching 7.6 × 10^–5 cm²/(V s) at an electric field of 8 × 10⁵ V/cm. Exploitation of a guest–host containing the tert-butylcarbazolyl and anthracene derivative as a host exhibiting triplet–triplet annihilation (TTA) and a fluorescent emitter resulted in an efficient hyperfluorescent OLED with a maximum external quantum efficiency of 7.1%. The OLED with such efficiency outperformed the theoretical limit of conventional fluorescence-based devices due to the utilization of triplet excitons in emission allocated to TTA upconverted excitons.

Due to the typical dielectric relaxation behavior of perovskite high-entropy ceramics (HECs), high-entropy engineering is beneficial for improving energy storage performance and has drawn extensive concern. In this study, high-entropy oxide (Bi_0.2Na_0.2Ba_0.2Sr_0.2Ca_0.2)(Ti_0.9Nb_0.1)O₃ (BNCBSTN)-modified 0.45(Bi_0.5Na_0.5)TiO₃-0.55(Sr_0.7Bi_0.2)TiO₃ (BNT-SBT) systems, BNT-SBT-xBNCBSTN (0 ≤ x ≤ 0.5) ceramics, were designed and prepared using a hydrothermal method. It is found that the introduction of BNCBSTN into BNT-SBT promotes the configuration entropy and induces strong dielectric relaxation behavior, thereby greatly improving the energy storage performance. In addition, grain refinement, increased resistivity, and widened band gap are achieved by the modification of BNCBSTN, leading to a significant enhancement of the breakdown electric field (E_b). Consequently, BNT-SBT-0.3BNCBSTN HEC exhibits a preeminent recoverable energy density (W_rec = 6.04 J/cm³) and energy storage efficiency (η = 85%) under an excellent E_b of 410 kV/cm as well as good temperature and frequency stability. The remarkable improvement in energy storage performance indicates that modifying the ferroelectric system with high-entropy oxide is a feasible approach for developing energy storage capacitors.