ACS Applied Materials & Interfaces最新文献

Broadening the alloyed CdSe_xTe_1-x region in the absorber layer is the key to preparing highly efficient CdTe-based solar cells (SCs). With CdSe prejunction doping, the diffusion distance via the non-in situ Se doping method is restricted, and the doping ions are difficult to completely diffuse through the whole absorber layer. Moreover, the commonly used p-type back contact material CuSCN shows efficient copper doping characteristics, but the S element is not an ideal doping source for the CdTe absorber. Thus, it is demanding to develop new materials with dual activation of copper and Se. In this paper, on the one hand, CuSeCN was used as a Se doping source on the back surface of the absorber to successfully form p-CdSeTe with a band gap of 1.438 eV. On the other hand, as an emerging copper-treated material, CuSeCN is able to enhance the carrier extraction rate and lower the Schottky barrier of the device, which exhibits similar hole activation performance to CuSCN. In addition, CdTe thin-film devices treated with CuSeCN exhibit higher PCEs than those of devices treated with a CuSCN/CdSe double layer. After optimizing the experimental conditions, the short current density of CuSeCN-doped CdTe thin-film solar cells increased from 28.03 to 30.02 mA/cm², the FF increased from 58.11 to 70.06%, and the power conversion efficiency was 17.48%. These results confirmed that CuSeCN is a promising candidate for both efficient carrier doping and lowering the band gaps of CdTe-based SCs.

The approaches to design and control intermolecular interactions for a selective enhancement of specific process(es) are of high interest in technologies using molecular materials. Here, we describe how π-π stacking enables control over the heavy-atom effect and spin-orbit coupling (SOC) through dimerization of an organic emitter in solid media. π-π interactions in a red thermally activated delayed fluorescence (TADF) emitter Ac-CNBPz afford specific types of dimers. In its brominated derivative Ac-CNBPzBr, the vicinity of the Br atom and the electronic density of the dimer involved in a spin-flip transition afford up to 200-fold increase of the SOC, in the most favorable case, attributed to the external heavy-atom effect (EHAE) of the halogen atom. The presence of such dimers in the films of Ac-CNBPzBr provides enhancement of reverse intersystem crossing, and thus, TADF occurs mostly within a few microseconds, up to 20 times faster than in Ac-CNBPz. For this reason, organic light-emitting diodes using Ac-CNBPzBr as an emitter and an assistant dopant show a decreased efficiency roll-off by a factor of 4 and 1.5, respectively. The crucial aspects of the intermolecular electronic interactions between a chromophore system and an HA together with the particularly favorable dimer geometry not only help to understand the nature of the EHAE but also provide guidelines for the molecular design of emitters for all-organic light-emitting devices with enhanced stability.

To achieve high-performance lithium-ion batteries (LIBs), controlling interfacial reactions at the electrode/electrolyte interface is intensely studied by introducing chemical additives into the electrolyte solution. These additives preferentially decompose over other electrolyte components, forming a stable interphase film at the electrode/electrolyte interface, which protects against capacity degradation and overcharging. However, the composite nature of conventional LIB electrodes makes it challenging to directly observe the electrochemical properties and formation process of the passivation film on the active material alone. To address this challenge, we used single-particle electrochemical measurement (SPEM), which uses an open-type measurement cell, enabling the direct observation of resistance component changes within a single particle during the in-situ introduction of additives. In this study, SPEM was applied to a LiCoO₂ single particle (LCO-SP) to evaluate changes in electrochemical and resistance properties with the in-situ introduction of an additive solution under a charged state. The electrolyte solution and additive used were 1.0 mol kg^-1 ethylene carbonate-LiN(SO₂F)₂, with LiPO₂F₂ as the additive avoiding concentration changes of LiN(SO₂F)₂. In the additive-free system, SPEM and AC impedance measurements revealed a single asymmetric semicircular arc, indicating resistance components related to the internal LCO SP, charge transfer, and the interphase layer at the electrode/electrolyte interface. In the additive-containing system (1.0 wt %), the semicircular arc from AC impedance measurements exhibited a decrease in time constant and slight noise, suggesting changes in the charge transfer process. Upon in-situ introduction of the additive under a charged state, the impedance spectra exhibited two semicircular arcs and an increasing trend in the resistance of their lower frequency component, while maintaining potential, attributed to the growth of the interphase layer at the LCO SP/electrolyte interface. Therefore, SPEM enables direct and precise observation of resistance behavior at the electrode/electrolyte interface on a single particle scale during additive introduction.

Electromagnetic wave absorption materials that can be utilized for freewill adhering or peeling from the target substrate remain a challenge to be solved. Compared to powder-based slurry and coatings, microwave absorption films possess clear advantages for their good flexibility and machinability. However, the matching thickness and effective bandwidth of 2D microwave absorption films cannot satisfy the current application requirements. As a result, it is necessary to complete a rational structural design based on flat films. In view of the fact that common film-forming methods based on blocks or hard bases cannot be changed or replaced easily once the structural construction is done, here solvent evaporation molding combined with phase change material filling was proposed for the first time to accomplish continuous structural transformation for flexible films. Unlike the original reflection loss (RL) peaks of flat films at around 17.0 GHz, a new absorption peak near 12.25 GHz was generated thanks to the design of coherent structures, resulting in the peaks' boundary merging and effective bandwidth extension. Specifically, 4.56 GHz of absorption bandwidth (RL < -5 dB) at 1.0 mm and 4.27 GHz (RL < -10 dB) of absorption bandwidth at 2.3 mm could be obtained by arch testing under electrical field polarization. Importantly, correlations between EM field polarizations and coherent structures as well as the rules of the absorption peak generation and frequency shift related to the structural variation have all been figured out. The presented laws of EM pattern evolutions for structural films in this work lay the foundation for the applications of high-efficiency microwave absorption materials in complex surfaces and switchable scenes.

Wide bandgap semiconductor AlGaN alloys have been identified as key materials to fabricate solar-blind ultraviolet photodetectors (SBUV PDs). Herein, a self-driven SBUV polarization-sensitive PD (PSPD) based on semipolar (112̅2)-oriented AlGaN films is reported. Using the flow-rate modulation epitaxy method, the full widths at half maximum (FWHMs) for the obtained (112̅2) AlGaN along [112̅3̅] and [11̅00] rocking curves are 0.205° and 0.262°, respectively, representing the best results for heteroepitaxial semipolar AlGaN so far. Density functional theory calculations and experimental results reveal that semipolar AlGaN possesses in-plane anisotropy. The self-driven (112̅2) AlGaN PSPDs exhibit strong polarization-sensitive photoresponse with a polarization ratio of 1.54 at 266 nm and rapid response of 450/450 ms compared to other low-dimensional semiconductor materials. More interestingly, we observe positive and negative photoresponse behaviors under UV light illumination due to surface states and charge transfer. Our results may enable potential applications in multifunctional SBUV optoelectronic devices.

Understanding lithium-ion dynamics across defect-rich grain boundaries (GBs) is crucial for solid-state electrolytes. This study examines local electronic and structural changes in a Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) solid electrolyte via X-ray absorption spectroscopy (XAS) and their correlation with ion transport properties. GBs were tailored through conventional isothermal sintering (CIS) and spark plasma sintering (SPS). Ti L_2,3-, Ti K-, O K-, and P L_2,3-edges from XAS revealed octahedral symmetry in bulk regions of both LATP-CIS and LATP-SPS. However, Ti L_2,3-edge spectra in total electron yield mode and Ti K-edge white line intensity shifts in LATP-SPS indicate lower oxidation states and structural distortions due to a significant amorphous GB fraction. Modulations in O K-edge and P L_2,3-edge spectra further highlight local structural differences in GB regions of LATP-CIS and LATP-SPS. Electron energy loss spectroscopy (EELS) also reveals variations in Ti L_2,3-edge splitting and pre-edge peak intensities, consistent with X-ray absorption near-edge spectroscopy analysis. LATP-SPS exhibits a higher Li content in the GB region than LATP-CIS. The GB ionic conductivity of LATP-SPS (σ_gb,300 K ∼ 1.36 × 10^-3 S/cm) is two orders higher than that of LATP-CIS (σ_gb,300 K ∼ 3.84 × 10^-5 S/cm), while grain conductivity remains similar. Trapping and hopping enthalpy estimations suggest that trapped Li ions contribute ∼27% of activation energy for LATP-SPS compared to ∼17% for LATP-CIS. Enhanced ion diffusion in polycrystalline LATP GBs is predicted from molecular dynamics simulations, where liquid-like ion pair correlations improve mobility. This work highlights the significant influence of GB-induced structural distortions, probed through XAS and EELS, on the ionic conductivity and charge transport in LATP electrolytes.

Understanding a catalytic reaction requires tools that elucidate the structure of the catalyst surface and subsurface, ideally at atomic resolution and under reaction conditions. Operando electron microscopy meets this requirement in some cases, but fails in others where the required reaction conditions cannot be reached or lead to an unwanted influence of the electron beam on the reactant and catalyst. We introduce ILIAS (identical location imaging and spectroscopy) in combination with a quasi in situ approach to disentangle the effect of heat and gas on the surface of nanoparticles from the effect of the electron beam. With this approach we allow high temperatures and pressures in any gaseous environment on the one hand, and atomic resolution imaging and spectroscopy on the other. As a proof of concept, we resolve the structural evolution of a Co₃O₄ spinel catalyst using ILIAS and track the oxidation state across the surface before and after heating in a reductive or oxidative environment. We then titrate the surface of the catalyst using CO as a probe molecule to remove highly active oxygen species formed during the thermal treatment, providing unprecedented insight into the interplay between pretreatment and surface reactivity of Co₃O₄ nanoparticles.

Photoelectrochemical (PEC) water splitting for hydrogen production is a promising technology for sustainable energy generation. In this work, we introduce Nd sites boost the PEC performance of Fe₂O₃ photoanodes through a precise gas-phase cation exchange process, which substitutes surface Fe atoms with Nd. The incorporation of Nd significantly enhances charge transfer properties, increases carrier concentration, and reduces internal resistance, leading to a substantial increase in photocurrent density from 0.44 to 0.92 mA cm^-2 at 1.23 V_RHE. Further enhancement of catalytic activity was achieved by depositing a NiCo(OH)_x layer and a photocurrent density of 1.15 mA cm^-2 at 1.23 V_RHE were obtained. Theoretical calculations corroborate these experimental results, revealing that Nd doping narrows the bandgap, improves charge separation efficiency, and lowers the reaction potential barrier, thereby accelerating water oxidation kinetics. These findings underscore the effectiveness of surface cation exchange and targeted metallic element doping in overcoming the intrinsic limitations of Fe₂O₃, providing a viable pathway for developing high-performance PEC systems for efficient hydrogen production.

Metal-semiconductor contact plays a significant role in devices such as transistors, photoemitters, and photodetectors. Here, the Au_xIn_y alloy contact gives a state-of-the-art low R_C (contact resistance) in GeSe devices. The R_C of GeSe-Au_xIn_y is measured to be 25 kΩ μm under channel carrier concentration around p = 2.490 × 10¹⁰ cm^-2. This low R_C is ascribed to a small barrier height of 16 meV. Our density functional theory calculation found the formation of a high conductive metallic GeSe-Au_xIn_y interface due to indium doping, which screens the possible interface disorder-induced gap states and metal-induced gap states that are observed when using pure In (indium) or Au (gold) metal. The GeSe-Au_xIn_y photodetectors show enhanced photoresponsivity with a specific photoresponsivity of 6.46 × 10⁴ A/W and a detectivity of 8.9 × 10¹³ Jones (at 450 nm wavelength). Our study is helpful in designing high-performance GeSe-based devices.

The rapid increase in electronic waste (e-waste) necessitates sustainable materials that combine functionality with recyclability. Here, we introduce a novel approach for creating flexible vitrimers─reprocessable polymers with dynamic covalent bonds─for use in electronic applications, such as wiring and connectors. By extending polymer chains and employing transesterification reaction, we develop vitrimers that exhibit tunable viscoelastic properties, high stretchability (over 250% tensile strain), and enhanced toughness (up to 466 J/m³). Our vitrimers demonstrate a topological freezing temperature (T_v) of 185-248 °C, adjustable through catalyst concentration and chain length. The materials are synthesized by using a two-step process involving widely available industrial chemicals. Molecular dynamics simulations provide insight into how chain extension and network topology affect viscoelasticity, supporting the experimental findings. Using transesterification, covalent bonding between flexible and rigid vitrimers can be achieved. We prototype a functional USB cable that successfully transfers power and data, showcases repairability, and is recyclable through a solvent-based process. These results highlight the potential of flexible vitrimers in reducing e-waste and advancing sustainable electronic manufacturing.