Strain Modulation for Light-Stable n-i-p Perovskite/Silicon Tandem Solar Cells.

Perovskite/silicon tandem solar cells are promising to penetrate photovoltaic market. However, the wide-bandgap perovskite absorbers used in top-cell often suffer severe phase segregation under illumination, which restricts the operation lifetime of tandem solar cells. Here, a strain modulation strategy to fabricate light-stable perovskite/silicon tandem solar cells is reported. By employing adenosine triphosphate, the residual tensile strain in the wide-bandgap perovskite absorber is successfully converted to compressive strain, which mitigates light-induced ion migration and phase segregation. Based on the wide-bandgap perovskite with compressive strain, single-junction solar cells with the n-i-p layout yield a power conversion efficiency (PCE) of 20.53% with the smallest voltage deficits of 440 mV. These cells also maintain 83.60% of initial PCE after 2500 h operation at the maximum power point. Finally, these top cells are integrated with silicon bottom cells in a monolithic tandem device, which achieves a PCE of 26.95% and improved light stability at open-circuit.

Photocatalytic decomposition of benzene by porous nanocrystalline ZnGa2O4 with a high surface area.

Porous nanocrystalline ZnGa2O4 catalysts were synthesized by a simple soft-chemical method at low temperature. The catalysts were characterized by XRD, nitrogen adsorption, SEM, TEM, UV/ vis, and FT-IR spectroscopy. The activity of the photocatalysts was evaluated by decomposition of benzene and its derivatives in the gas phase. It was found that hydrothermal treatment resulted in the formation of spinel ZnGa2O4 with a large surface area of 43-201 m2 x g(-1) depending on the synthetic temperature. The optimum synthetic temperature was found to be 80 degrees C, at which the sample possessed a surface area of 201 m2 x g(-1) and had the highest photocatalytic activity for degrading benzene. A comparison with TiO2 and Pt/TiO2 showed that the ZnGa2O4 (synthesized at 80 degrees C) had improved photocatalytic activity and durability over the TiO2-based catalysts. No remarkable deactivation of the ZnGa2O4 catalyst was observed in 80 h photoreaction, whereas the TiO2 deactivated remarkably in 24 h reaction. The high photocatalytic performance of porous ZnGa2O4 catalysts can be explained by the large specific surface area, the accessible porous framework, and the high redox power.

Nanostructuring cadmium germanate catalysts for photocatalytic oxidation of benzene at ambient conditions.

A nanostructured Cd(2)Ge(2)O(6) photocatalyst was successfully prepared by a hydrothermal process. The photocatalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV/vis, N(2) adsorption-desorption, and Fourier transform infrared (FTIR) techniques. The photocatalytic property of the material was evaluated via the decomposition of benzene in the gas phase with light illumination and was compared with that of commercial titania (Degussa P25) and Pt/TiO(2). The electronic band structure of Cd(2)Ge(2)O(6) was analyzed by density functional theory (DFT) calculation. Results reveal that the prepared Cd(2)Ge(2)O(6) has unique geometric and electronic properties, which in combination with its superior textural properties makes it a new semiconductor photocatalyst for environmental purification of benzene in air with molecular oxygen under ambient conditions. It was also found that the Cd(2)Ge(2)O(6) was more active and stable than TiO(2)-based catalysts in the photocatalytic decomposition of other volatile aromatic pollutants including toluene and ethylbenzene. The enhanced photocatalytic performance of Cd(2)Ge(2)O(6) can be explained by the special band structure, and geometric and electronic feature, in unison with the high surface area nanoporous framework.