Micropatterning
is considered a promising strategy for improving
the performance of electrochemical devices. However, micropatterning
on ceramic is limited by its mechanically fragile properties. This
paper reports a novel imprinting-assisted transfer technique to fabricate
an interlayer structure in a protonic ceramic electrochemical cell
with a micropatterned electrolyte. A dense proton-conducting electrolyte,
BaCe0.7Zr0.1Y0.1Yb0.1O3−δ, is micropatterned in a chevron shape with
the highest aspect ratio of patterns in electrode-supported cells
to the best of our knowledge, increasing surface areas of both electrode
sides more than 40%. The distribution of relaxation time analysis
reveals that the chevron-patterned electrolyte layer significantly
increases the electrode contact areas and active electrochemical reaction
sites at the vicinity of the interfaces, contributing to enhanced
performances of both the fuel cell and electrolysis operations. The
patterned cell demonstrates improved fuel cell performance (>45%)
and enhances electrolysis cell performance (30%) at 500 °C. This
novel micropatterning technique is promising for the facile production
of layered electrochemical cells, further opening a new route for
the performance enhancement of ceramic-based electrochemical cells.
Gallium oxide (Ga2O3) is a promising semiconductor for next-generation high-power electronics due to its ultra-wide bandgap and high critical breakdown field. To utilize its unique electrical properties for real-world applications, an accurate description of its electronic structure under device-operating conditions is required. Although the majority of first-principles models focus on the ground state, temperature effects govern the key properties of all semiconductors, including carrier mobility, band edge positions, and optical absorption in indirect gap materials. We report on the temperature-dependent electronic band structure of β-Ga2O3 in a wide temperature range from T = 0 to 900 K using first-principles simulations and optical measurements. Band edge shifts from lattice thermal expansion and phonon-induced lattice vibrations known as electron–phonon renormalization are evaluated by utilizing the quasi-harmonic approximation and the recently developed “one-shot” frozen phonon method, respectively. Electron–phonon effects and thermal expansion together induce a substantial temperature-dependence on the bandgap, reducing it by more than 0.5 eV between T = 0 and 900 K, larger than that observed in other wide bandgap materials. Key implications, including an increase in carrier concentrations, a reduction in carrier mobilities due to localization of band edge states, and an ∼20% reduction in the critical breakdown field, are discussed. Our prediction of temperature-dependent bandgap matches very well with experimental measurements and highlights the importance of accounting for such effects in first-principles simulations of wide bandgap semiconductors.
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