Searching for compatible electrolytes with Ni 0.8 Co 0.15 Al 0.05 LiO 2 (NCAL) electrodes with high ionic conductivity at low operational temperatures (<550 °C) is essential for the research on ceramics fuel c...
Searching for compatible electrolytes with Ni 0.8 Co 0.15 Al 0.05 LiO 2 (NCAL) electrodes with high ionic conductivity at low operational temperatures (<550 °C) is essential for the research on ceramics fuel cells (CFCs). In this work, the experimental and theoretical analyses demonstrate that the highly stable single-phase Gd 3 Ga 5 O 12 (GGO) garnet structure, composed of Gd-O octahedrons and Ga-O tetrahedrons, provides more active sites for ion transport, resulting in enhanced peak power density (PPD) and stable open circuit voltage (OCV) at low operational temperature. The unique internal garnet structure effectively reduces the interfacial impedance of the prepared fuel cell device, provides many active sites at triple-phase boundaries and increases the electrochemical stability. As a result, the constructed cell can deliver a superior peak power density of 770 mW/cm 2 at 490 °C. In addition, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy and theoretical calculations further demonstrate electrolyte effectiveness of GGO, enabling stable OCV even at a low temperature of 370 °C under a H 2 /air environment. This work can help in improving the understanding of the underlying mechanisms of a single-layer fuel cell device, which is essential to further develop this potential energy technology even at a very low temperature of 370 °C.
Decreasing perovskite nanocrystal size increases radiative recombination due to the quantum confinement effect, but also increases the Auger recombination rate which leads to carrier imbalance in the emitting layers o...
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Decreasing perovskite nanocrystal size increases radiative recombination due to the quantum confinement effect, but also increases the Auger recombination rate which leads to carrier imbalance in the emitting layers of electroluminescent devices. Here, we overcome this trade-off by increasing the exciton effective mass without affecting the size, which is realized through the trace Cd 2+ doping of formamidinium lead bromide perovskite nanocrystals. We observe an ~2.7 times increase in the exciton binding energy benefiting from a slight distortion of the [BX 6 ] 4− octahedra caused by doping in the case of that the Auger recombination rate is almost unchanged. As a result, bright color-saturated green emitting perovskite nanocrystals with a photoluminescence quantum yield of 96 % are obtained. Cd 2+ doping also shifts up the energy levels of the nanocrystals, relative to the Fermi level so that heavily n -doped emitters convert into only slightly n -doped ones; this boosts the charge injection efficiency of the corresponding light-emitting diodes. The light-emitting devices based on those nanocrystals reached a high external quantum efficiency of 29.4 % corresponding to a current efficiency of 123 cd A −1 , and showed dramatically improved device lifetime, with a narrow bandwidth of 22 nm and Commission Internationale de I'Eclairage coordinates of (0.20, 0.76) for color-saturated green emission for the electroluminescence peak centered at 534 nm, thus being fully compliant with the latest standard for wide color gamut displays.
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