One-Step Synthesis of Porous Transparent Conductive Oxides by Hierarchical Self-Assembly of Aluminum-Doped ZnO Nanoparticles

Abstract

Transparent conductive oxides (TCOs) are highly desirable for numerous applications ranging from photovoltaics to light-emitting diodes and photoelectrochemical devices. Despite progress, it remains challenging to fabricate porous TCOs (pTCOs) that may provide, for instance, a hierarchical nanostructured morphology for the separation of photoexcited hole/electron couples. Here, we present a facile process for the fabrication of porous architectures of aluminum-doped zinc oxide (AZO), a low-cost and earth-abundant transparent conductive oxide. Three-dimensional nanostructured films of AZO with tunable porosities from 10 to 98% were rapidly self-assembled from flame-made nanoparticle aerosols. Successful Al doping was confirmed by X-ray photoemission spectroscopy, high-resolution transmission electron microscopy, elemental mapping, X-ray diffraction, and Fourier transform infrared spectroscopy. An optimal Al-doping level of 1% was found to induce the highest material conductivity, while a higher amount led to partial segregation and formation of aluminum oxide domains. A controllable semiconducting to conducting behavior with a resistivity change of more than 4 orders of magnitudes from about 3 × 102 to 9.4 × 106 Ω cm was observed by increasing the AZO film porosity from 10 to 98%. While the denser AZO morphologies may find immediate application as transparent electrodes, we demonstrate that the ultraporous semiconducting layers have potential as a light-driven gas sensor, showing a high response of 1.92–1 ppm of ethanol at room temperature. We believe that these tunable porous transparent conductive oxides and their scalable fabrication method may provide a highly performing material for future optoelectronic devices.

From Stochastic Self‐Assembly of Nanoparticles to Nanostructured (Photo)Electrocatalysts for Renewable Power‐to‐X Applications via Scalable Flame Synthesis

“…Depending on the synthesis parameters such as atomization pressure, nature of materials, high temperature residence time, or temperature of substrates, the variety of physiochemical properties and morphologies of target nanomaterial are obtained. For example, highly porous films with fractal dimensions of ≈1.75 are obtained when materials have high melting/sintering points, and the temperature of substrates are retained low such as fractal ZnO, [49,50] TiO 2 , [25,51] or SnO 2 , [52] while larger stubby, oblong or columnar structures are achieved when the substrate temperature is high, and material has relatively low melting/ sintering temperatures such as BiVO 4 , [53] Bi 2 O 3 , [54,55] Co 3 O 4 [56] or WO 3 . [57] Fabrication of multicomponent/multiphases might be limited with the use of a single nozzle FSP as a uniformed distribution of each component in a multicomponent structure, rather than discrete individual component, is often obtained, i.e., the flexibility in tuning grain boundaries in a singlenozzle FSP system is limited.…”

“…Besides, multicomponents or multilayer coating are some of the featured compositions can be achieved using FSP. [106,107] For example, doping different metal elements into a metal oxide crystal structure such as Al-doped ZnO, [50] Ce-doped MnO, [108] Sb-doped Fe 2 O 3 , [109] to name a few. [45,70,110] The mixing/blending behaviors during the particle formation, the precursors and solvent composition, the evaporation and nucleation rates are among the synthesis parameters that dictate the distribution and composition of the outcome catalysts.…”

Zinc Oxide‐Based Acetone Gas Sensors for Breath Analysis: A Review

“…On the other hand, high‐temperature annealing of the ZnO nanostructures results in the agglomeration of nanostructured ZnO into large entities. Furthermore, the acetone sensors tend to lose their response with time at very high temperature due to thermal ripening of the sensing materials, which negatively affect the long‐term stability of the sensor [39–42] …”

Paper‐Like Writable Nanoparticle Network Sheets for Mask‐Less MOF Patterning

“…With respect to the broader applicability of our method, it is important to note that our proposed approach is compatible with the broad family of CVD‐generated MOFs. [ 13,23,24,31 ] As the flame aerosol synthesis approach, utilized here, is capable to synthesize a large family of metal oxides, [ 39 ] which makes it an ideal tool for synthesizing nanoparticle precursor sheets for various MOFs. To demonstrate this concept, we have now converted MIL‐53 (Figures S10 and S11, Supporting Information) and HKUST‐1 films (Figures S12 and S13, Supporting Information) from Fe 2 O 3 and CuO NN precursor sheets, respectively.…”