Design of Ordered Mesoporous CeO₂–YSZ Nanocomposite Thin Films with Mixed Ionic/Electronic Conductivity via Surface Engineering

Abstract

Mixed ionic and electronic conductors represent a technologically relevant materials system for electrochemical device applications in the field of energy storage and conversion. Here, we report about the design of mixed-conducting nanocomposites by facile surface modification using atomic layer deposition (ALD). ALD is the method of choice, as it allows coating of even complex surfaces. Thermally stable mesoporous thin films of 8 mol-% yttria-stabilized zirconia (YSZ) with different pore sizes of 17, 24, and 40 nm were prepared through an evaporation-induced self-assembly process. The free surface of the YSZ films was uniformly coated via ALD with a ceria layer of either 3 or 7 nm thickness. Electrochemical impedance spectroscopy was utilized to probe the influence of the coating on the charge-transport properties. Interestingly, the porosity is found to have no effect at all. In contrast, the thickness of the ceria surface layer plays an important role. While the nanocomposites with a 7 nm coating only show ionic conductivity, those with a 3 nm coating exhibit mixed conductivity. The results highlight the possibility of tailoring the electrical transport properties by varying the coating thickness, thereby providing innovative design principles for the next-generation electrochemical devices.

Inkjet‐Printed Narrow‐Channel Mesoporous Oxide‐Based n‐Type TFTs and All‐Oxide CMOS Electronics

“…Cu peaks were visible only at low temperatures (275 °C), in agreement with previous findings (existence of a pure copper phase at low temperature) for the synthesis via polyol method (with polyols, such as ethylene glycol, glycerol, etc., acting as reducing agents). [ 28 ] Up to 300 °C, the major phase observed was Cu 2 O. In contrast, when the precursor was annealed at 350 °C, it was essentially a mixture of Cu 2 O and CuO, with CuO being the primary phase.…”

“…Initially, the process conditions of Cu x O have been optimized, including the most suitable temperature, to obtain the best performance and a high device mobility (0.5 cm 2 V −1 s −1 ) that can be reproducibly achieved. Next, a suitable polymer structure-directing agent, polyisobutylene-b-poly(ethylene oxide), (PIB) 107 −(PEO) 150 , [27,28] has been used to prepare high surfaceto-volume ratio (mesoporous) thin film of In 2 O 3 at an identical process temperature of 350 °C to ensure facile single-step fabrication of the CMOS electronics. Mesoporous In 2 O 3 has been chosen to create 3D bulk transistors with composite solid polymer electrolyte (CSPE)-based electrolytic gating.…”

Understanding the Impedance of Mesoporous Oxides: Reliable Determination of the Material-Specific Conductivity

“…Thus, the characterization of the impact of the regular pore structure on the electrical properties is of great importance. In particular, the high number of interfaces, i.e., the grain boundaries between the single nanocrystallites as well as the surface area, can have a pronounced effect and may even dominate the overall behavior. ,, Electrochemical impedance spectroscopy is one of the most common methods to characterize charge transport in oxide ceramics. , It allows distinguishing between electric migration processes with different relaxation times, such as transport through single grains and across grain boundaries. Both processes appear as two separate semicircles in the Nyquist representation of the impedance, at least for microcrystalline samples .…”

Harnessing the Potential of Porous ZnO Photoanodes in Dye-Sensitized Solar Cells by Atomic Layer Deposition of Mg-Doped ZnO

“…The ALD process relies on the alternate and sequential exposure of the substrate to two or more vapor-phase precursors that react in self-limiting surface reactions between the functional groups on the substrate and the vapor-phase precursors. Coating of complex inner surfaces, even in porous thin films and nanocomposites, renders ALD superior compared to competing coating methods. , Those advantages have led to widespread applications in photovoltaics where ALD is used for the growth of passivation layers, passivating contacts, transparent conductive oxides in collectors, and protective layers in perovskite solar cells, − tandem solar cells, − and DSSCs − as well as other applications. − One approach for expanding the regular two-step ALD cycle toward advanced materials like ternary oxides consists of the use of supercycles. In this approach, two regular two-step ALD cycles are alternated and repeated to produce multilayered or mixed, multinary thin films.…”

“…Coating of complex inner surfaces, even in porous thin films and nanocomposites, renders ALD superior compared to competing coating methods. 21,22 Those advantages have led to widespread applications in photovoltaics where ALD is used for the growth of passivation layers, passivating contacts, transparent conductive oxides in collectors, and protective layers in perovskite solar cells, 23−25 tandem solar cells, 26−28 and DSSCs 29−34 as well as other applications. 35−38 One approach for expanding the regular two-step ALD cycle toward advanced materials like ternary oxides consists of the use of supercycles.…”