Spectral Splitting Solar Cells Consisting of a Mesoscopic Wide-Bandgap Perovskite Solar Cell and an Inverted Narrow-Bandgap Perovskite Solar Cell.

In comparison to monolithic perovskite/perovskite double-junction solar cells, a four-terminal spectrum-splitting system is a simple method to obtain a higher power conversion efficiency (PCE) because it has no constraints of unifying the structures of the top and bottom cells. In this work, utilizing the fact that low-bandgap Sn-Pb bottom cells work the best in p-i-n while Pb-based wide-bandgap top cells work better in an n-i-p architecture, a wide-bandgap (Eg = 1.61 eV) perovskite solar cell with a mesoscopic structure and a narrow-bandgap (Eg = 1.27 eV) perovskite solar cell with an inverted structure were combined to fabricate a double-junction four-terminal spectral splitting solar cell. The double-junction solar cell with the 801 nm spectral splitting with an active area of 0.18 cm2 was found to work with a PCE of 25.3%, which is the highest reported so far for a 4-T all-perovskite double-junction spectral splitting solar cell.

Magnetic Fe3O4-Supported Gold Nanoflowers with Lattice-Selected Surfaces: Preparation and Catalytic Performance.

Nanoflowers (NFs)-shape-controlled noble metal nanocrystals-have garnered significant attention because of their novel catalytic properties and applicability. In this paper, we report the preparation and catalytic performance of a magnetic Fe3O4-supported AuNF catalyst with a clean surface. The magnetically supported AuNFs were obtained by using magnetic Fe3O4 as the support. However, when nonmagnetic γ-Al2O3 was utilized as the support, the AuNFs did not exhibit a magnetic response. These supported AuNFs were utilized to catalyze the oxidation of 1-phenylethyl alcohol to acetophenone using air (1 atm) as the oxidant. The rate of formation of acetophenone using supported AuNFs was 8-fold higher than that of acetophenone using supported spherical Au nanoparticles of comparable size. In addition, the Fe3O4-supported AuNFs exhibited a higher rate of formation of acetophenone than the Al2O3-supported AuNFs. The Fe3O4-supported AuNFs were recovered using a magnet, and the recovered catalyst was reused under identical catalytic reaction conditions. The rate of formation of acetophenone using recovered Fe3O4-supported AuNFs remained unchanged, demonstrating no loss of catalytic activity.

Au-Ag Nanoflower Catalysts with Clean Surfaces for Alcohol Oxidation.

Shape-controlled metal nanocrystals, such as nanowires and nanoflowers, are attractive owing to their potentially novel catalytic properties and bimetallic nanocrystals composed of two distinct metals are expected to act as highly active catalysts. However, their catalytic activities are limited because of the capping agents adsorbed on the metal surfaces, which are necessary for the preparation and dispersion of these nanocrystals in solvents. Therefore, the preparation of bimetallic shape-controlled noble metal nanocrystals with clean surfaces, devoid of almost all capping agents, are expected to have high catalytic activity. Herein, we report the preparation of bimetallic Au-Ag nanoflowers using melamine as the capping agent. The bimetallic Au-Ag nanoflowers with a clean surface were subsequently obtained by a support and extraction method. The bimetallic nanoflowers with a clean surface were then used for the aerobic oxidation of 1-phenylethyl alcohol and they exhibited high rates for the formation of acetophenone compared to Au nanoflowers and spherical nanoparticles with almost the same size and Au/Ag ratio. We also show that Au-Ag nanoflowers containing only 1 % Ag (Au99 -Ag1 NFs) exhibit the highest rate of acetophenone formation among Au-Ag nanoflowers with different Au/Ag ratios owing to an increase in the electron density of the Au atoms that act as active sites for the oxidation of 1-phenylethyl alcohol.