查看更多>>摘要：Since the invention of MXenes (Ti3C2Tx), they have been positioned as a booming class of two-dimensional (2D) nanomaterials for energy conversion and storage applications. These extraordinary features arise from their surface functionalization, their high electrical conductivity, their outstanding dispersion in a variety of solvents, and the presence of several functional groups on their surfaces. However, the presence of van der Waals interactions results in the stacking of the 2D nanosheets of MXenes, like other 2D nanomaterials. This stacking results in a reduction in the number of active sites and poor ionic kinetics, which in turn reduces the activity of the material and hence the performances of MXene-based devices. Therefore, the conversion of 2D MXenes into three-dimensional (3D) MXene architecture has been shown to be an effective technique for reducing restacking, resulting in higher porosity, increased specific surface areas, and shorter mass and ion transportation distances in comparison to 1D and 2D architectures. Herein, we have attempted to summarize commonly used methodologies, such as assembly, templating, 3D printing, electrospinning, and gas foaming, for the construction of 3D MXenes and MXene-based moieties for their potential application as electrocatalytic materials. Further, the structure–property correlation of 3D MXene architectures are also given special consideration. Finally, related challenges and probable future prospects of 3D MXenes have also been discussed.
Kim YewonKim KwonyoungKim OkhyeonPark Chang Yup...
8页
查看更多>>摘要：To realize three-dimensional vertical phase-change random-access memory (PCRAM) devices, it is essential to fabricate highly conformal GeSbTe (GST) films inside high-aspect-ratio holes using atomic layer deposition (ALD). Different compositions of GST films are favored for various applications of PCRAM devices. In the present work, the [Ge]/[Sb] ratio of GST thin films prepared by tellurization annealing of ALD Ge–Sb films was controlled through the supercycle process of ALD GeSb and ALD Sb. By adjusting the cycle number ratio of ALD Sb to ALD GeSb between 0 and 0.5, we could change the Ge content of the Ge–Sb film from 0.33 to 0.66 and the Sb content from 0.26 to 0.63. After tellurization annealing at 230 °C, the Ge, Sb, and Te concentrations were 0.11–0.25, 0.19–0.37, and 0.52–0.60, respectively. The phase transition temperature was tunable between 90 and 137 °C depending on the Sb concentration. A crystalline GST film with a uniform composition close to Ge2Sb2Te5 was formed, with a step coverage of higher than 85% on a trench pattern with an aspect ratio of 24.
查看更多>>摘要：We demonstrate a reliable monolithic process to fabricate micro-light-emitting diodes (μLEDs) driven by highly stable dual-gate structured amorphous indium gallium zinc oxide (a-IGZO) thin-film transistor (TFT) arrays. In contrast to the conventional μLED integration technologies that require the mass transfer of LEDs, our unique monolithic fabrication of oxide TFTs on the GaN epitaxial layer can be applied for accurate integration compared to the method of mounting discrete μLEDs on a backplane individually. To evaluate the applicability of the method at the wafer level, we introduced an atomic-layer-deposited Al2O3 insulator film and a denser oxide semiconductor in a dual-gate structured TFT. The induction of controlled hydrogen diffusion from the gate insulator into the active layer at low temperatures led to the good performance of the dual-gate bottom-contact (DGBC) a-IGZO TFTs under positive bias temperature stress (PBTS), negative bias illumination stress (NBIS), and negative bias temperature illumination stress (NBTIS). Monolithic integration of such μLEDs and DGBC a-IGZO TFT arrays was achieved using an organic interlayer dielectric at a low temperature below 230 °C. This simple process exhibits excellent TFT manufacturability (stable Von = 0.78 V), stability (ΔVon, PBTS: 0.03 V, NBIS: ?1.85 V, and NBTIS: ?3.27 V), uniformity, and reproducibility (less than 4% difference in Von). It shows promise for the mass production of μLED displays for flexible and/or ultra-high-resolution displays for augmented and virtual reality and biomedical applications.
查看更多>>摘要：Single-halogen CsPbI3 is a promising candidate for red light-emitting diodes due to its high photoluminescence quantum yield, narrow emission line width, and facile solution processability. However, the bandgap of CsPbI3 is not in the range of the display-oriented pure red band (620–660 nm). In this study, the introduction of a phenylbutylammonium bromide (PBABr) ligand can not only tune the bandgap of the resulting low-dimensional CsPbI3 films but also induce the formation of a concentrated quantum-well structure at n = 3 domains, which contributes to better energy transfer and charge transport. As a result, low-dimensional PBABr capped CsPbI3 films with tunable emissions covering the pure red band were obtained and the corresponding efficient electroluminescent devices were achieved. By further optimizing the device structure and interface, a highly efficient red (653 nm) light-emitting diode device was fabricated with a maximum EQE of 14.3% and a maximum brightness of 543 cd m?2. This work provides a facile one-step strategy by bromine-terminated ligand treatment to realize low-dimensional CsPbI3 films with desirable optical properties and preferred quantum-well distribution for display applications.
查看更多>>摘要：Different interface engineering approaches have been adopted for development of high efficiency and stable perovskite solar cells (PSCs). In this work, we report our efforts for realizing high efficiency PSCs using a poly(methyl methacrylate) (PMMA):2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ)-modified poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine) (PTAA) hole-transporting layer (HTL). The results reveal that PMMA molecules on PTAA induce an interface dipole at the PTAA/perovskite interface, caused by the electrostatic interaction between the ester groups in the PMMA molecules and the electron-deficient N+ free radicals in the PTAA molecules. The existence of the PMMA-induced interface dipole at the PTAA/perovskite interface increases the built-in potential in the PSCs, resulting in a 60 mV increase in the open circuit voltage. The increase in the built-in potential aids in an efficient charge collection process. The incorporation of F4-TCNQ molecules into PMMA further promotes the hole extraction by creating an intermediate state. In addition, PMMA and F4-TCNQ, especially PMMA, also passivate interface defects and promote perovskite crystallization. As a result, the MAPbI3-based PSCs with a PMMA:F4-TCNQ-modified PTAA HTL achieve a power conversion efficiency of >20%, which is evidently higher than that of a control PSC with a pristine PTAA HTL (～17%). Moreover, the stability of PSCs is also improved efficiently. Our findings unveil the importance of PMMA:F4-TCNQ interfacial modification for mitigating charge recombination loss through controlled growth of the perovskite semiconductor layer, reduced interface defects and high built-in potential for efficient operation of the PSCs.
查看更多>>摘要：Although the power conversion efficiency (PCE) of organic solar cells (OSCs) has been increased to over 19% under 1 sun illumination, stability is still a shortcoming which impedes commercialization; this has motivated researchers to pay more attention to this issue. Herein we report two types of all-polymer blends: a traditional donor–acceptor pair of PM6:PY-IT; and a one-pot synthesized, multicomponent example called PM6-b-PY-IT, and these exhibit different performance changes under external stress. The PM6-b-PY-IT device has a PCE of 13.63% which is lower than that of 15.24% for PM6:PY-IT, but it has better operational stability under continuous illumination and better thermostability, thereby realizing greater power output over a period of one month. Morphology characterization and thermal degradation process studies reveal that the PM6-b-PY-IT system can overcome stress, probably due to the existence of chemical bonding between the donor and acceptor phase/block, which enables stable phase separation, while excessive phase segregation in the binary all-polymer blend seriously undermines the device performance. This work provides a novel way of achieving high stability OSCs derived from a well-established all-polymer blend, which hopefully will enhance the marketing prospects for this photovoltaic technology.
查看更多>>摘要：Surface lattice resonance (SLR) is a collective resonance induced by radiative coupling between localized resonances in periodically arranged nanoparticles. Compared with metal nanoparticles, which have been conventionally utilized to realize SLRs, dielectric nanoparticles with a high refractive index and low absorption coefficient can achieve spectrally sharper resonances. Although titania (TiO2) is a transparent material with a high refractive index and is used as a representative scatterer in the visible region, TiO2 has absorption at energies higher than near-ultraviolet (UV). As an alternative to TiO2, in this study, we fabricated periodic nanoparticle arrays composed of zirconia (ZrO2), which is transparent in the near-UV region. ZrO2 nanoparticle arrays are fabricated via the thermal oxidation of ZrN nanoparticle arrays and support SLRs of both electric and magnetic natures. As a demonstration, we examined photoluminescence (PL) enhancement of the emitter layer on the nanoparticle array. Compared with the TiO2 nanoparticle arrays with identical design, the PL enhancement by the ZrO2 nanoparticle arrays is larger under excitation with near-UV light, whereas it is comparable under visible excitation. These results indicate that ZrO2 nanoparticle arrays are beneficial for applications involving light in the near-UV region.
NSTL
Royal Soc Chemistry