Metal oxide semiconductors are important due to their diverse set of applications in (opto)electronics including light-emitting diodes, solar cells, and thin film transistors (TFTs). However, compared to their n-type counterparts, p-type oxide thin films are less often reported, and there is a need for increased fundamental understanding of their process-structure–property relationships. In this study, p-type CuO x was grown by plasma-enhanced atomic layer deposition (PE-ALD) using different ratios of hydrogen and oxygen plasma and a nonfluorinated copper amidinate precursor. This approach, combined with postdeposition annealing, enables tuning of the phase, oxidation state, and morphology of the films. Here, we comprehensively investigate the coupled relationships between: (1) PE-ALD process parameters; (2) oxidation state, composition, and grain size; and (3) electronic properties of the films. Synchrotron X-ray absorption spectroscopy was performed to quantify the copper oxidation states. By varying the hydrogen:oxygen plasma ratio, the phase of CuO x can be controlled to form Cu, Cu2O, or CuO. Vacuum annealing resulted in an increase in grain size and reduction in copper oxidation state. To study the p-type semiconductor behavior, bottom-gate TFTs were fabricated, demonstrating characteristic I–V behavior with an on/off current ratio of ∼105 for the film with the largest Cu(I) fraction and largest grain size.
Highly transparent photocatalytic self-cleaning surfaces capable of harvesting near-visible (365−430 nm) photons were synthesized and characterized. This helps to address a current research gap in self-cleaning surfaces, in which photocatalytic coatings that exhibit activity at wavelengths longer than ultraviolet (UV) generally have poor optical transparency, because of broadband scattering and the attenuation of visible light. In this work, the wavelength-dependent photocatalytic activity of Ptmodified TiO 2 (Pt-TiO 2 ) particles was characterized, which exhibited activity for wavelengths up to 430 nm. Pt-TiO 2 nanoparticles were embedded in a mesoporous SiO 2 sol−gel matrix, forming a superhydrophilic surface that allowed for water adsorption and formation of reactive oxide species upon illumination, resulting in the removal of organic surface contaminants. These self-cleaning surfaces only interact strongly with near-visible light (∼365−430 nm), as characterized by photocatalytic self-cleaning tests. Broadband visible transparency was preserved by generating a morphology composed of small clusters of Pt-TiO 2 surrounded by a matrix of SiO 2 , which limited diffuse visible light scattering and attenuation. The wavelength-dependent self-cleaning rate by the films was quantified using stearic acid degradation under both monochromatic and AM1.5G spectral illumination. By varying the film morphology, the average transmittance relative to bare glass can be tuned from ∼93%−99%, and the self-cleaning rate can be adjusted by more than an order of magnitude. Overall, the ability to utilize photocatalysts with tunable visible light activity, while maintaining broadband transparency, can enable the use of photocatalytic self-cleaning surfaces for applications where UV illumination is limited, such as touchscreen displays.
transistors. [5] Polymer-based MIECs contain two principal components, one for electronic conduction and the other for ionic conduction. Each of these components should meet the molecular packing requirements for charge transport and both components should arrange in cocontinuous morphologies with percolation pathways for charge transport in three dimensions. Yet, achieving such structures relevant for MIECs has not been straightforward. At present, several different strategies are used to design and fabricate MIECs. They are: (1) mixing of conjugated polymers and polyelectrolytes [e.g., poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)], [5,6,8,9] (2) imbibing ionic fluids in conjugated polymer films, [11] (3) incorporating ion conducting side chains on conjugated polymers, [12][13][14][15][16] (4) ion-doped [17][18][19][20] or oxidized [21] conjugated polymers, and (5) diblock copoly mer with ion conducting and electronic conducting polymers as the constituent blocks [e.g., poly(3-hexylthiophene)-bpoly(ethylene oxide) (P3HT-b-PEO)]. [2,3] However, these methods do not afford separate and systematic control over the morphology and properties of the ionic and electronic conducting phases while keeping the overall morphology constant. The central problem is the lack of a general approach to control the molecular packing and morphology in MIECs. We report here an approach, based on polymer nanoparticle selfassembly, to fabricate polymer-based MIECs. This approach provides a pathway to achieve tailored molecular order for each component on the nanoscale (<100 nm) and targeted assembly of the components on the mesoscale (>100 nm-100 µm). We demonstrate the efficacy of this approach for fabricating MIECs through binary nanoparticle assemblies of electronically conducting and Li-ion conducting polymer nanoparticles (see Figure 1a).Nanoparticle self-assembly is emerging as a powerful tool to design and fabricate mesoscale assemblies and interfaces. [22][23][24][25] For polymer-based materials, they provide a unique pathway to generate complex structures and co-assemblies under nonequilibrium processing conditions with macroscopic homogeneity and compositional flexibility. In this strategy, we first fabricate polymer components as nanoparticles, and then use them as building blocks for further assembly to create Polymer-based mixed ionic-electronic conductors (MIECs) are desired for both bulk and interfacial materials in next-generation energy storage and electronic devices. Polymer-based MIECs contain two principal components, one for electronic conduction and the other for ionic conduction. The central problem is the lack of a general approach to control the molecular packing and morphology of the constituent components that will afford the ability to easily tune transport properties. This study demonstrates the efficacy of a modular method based on polymer nanoparticle self-assembly to achieve MIECs with tunable conductivity. This work uses poly(3-hexylthiophene) nanoparticles as the electronic conductor and li...
We demonstrate tunable structural color patterns that span the visible spectrum using atomic layer deposition (ALD). Asymmetric metal–dielectric–metal structures were sequentially deposited with nickel, zinc oxide, and a thin copper layer to form an optical cavity. The color response was precisely adjusted by tuning the zinc oxide (ZnO) thickness using ALD, which was consistent with model predictions. Owing to the conformal nature of ALD, this allows for uniform and tunable coloration of non-planar three-dimensional (3D) objects, as exemplified by adding color to 3D-printed parts produced by metal additive manufacturing. Proper choice of inorganic layered structures and materials allows the structural color to be stable at elevated temperatures, in contrast to traditional paints. To print multiple colors on a single sample, polymer inhibitors were patterned in a desired geometry using electrohydrodynamic jet (e-jet) printing, followed by area-selective ALD in the unpassivated regions. The ability to achieve 3D color printing, both at the micro- and macroscales, provides a new pathway to tune the optical and aesthetic properties during additive manufacturing.
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