Oriented Attachment as the Mechanism for Microstructure Evolution in Chloride-Derived Hybrid Perovskite Thin Films.

Hybrid organic-inorganic perovskites with appealing optoelectronic properties have attracted significant interest for photovoltaic application. The use of chloride (Cl-)-containing species to induce improved perovskite thin-film microstructures and improved optoelectronic properties is well-established. However, the mechanism for the formation of perovskite films with highly textured, micron-sized grains in the presence of Cl- is not well established. Using synchrotron-based in situ two-dimensional grazing incidence wide-angle X-ray scattering complemented by scanning electron microscopy imaging, we present an oriented attachment mechanism via mineral bridge formation for the microstructural evolution of perovskite films post-treated with methylammonium chloride. We have identified the crucial role of the chlorine-containing intermediate phase as the mineral bridge, which enables the reorientation of primary, nanoscale perovskite grains followed by fusion into uniaxial oriented quasi-single crystal grains. The resulting perovskite films exhibit micron-sized grains with preferential orientation of the tetragonal (110) direction perpendicular to the substrate, resulting in improved solar cell efficiency attributed to improved charge collection. Our findings help to understand the fundamental mechanisms of microstructure evolution via soft processing in hybrid perovskite films.

Oxygen vacancy induced Bi2WO6 for the realization of photocatalytic CO2 reduction over the full solar spectrum: from the UV to the NIR region.

Photocatalytic CO2 reduction over the UV-Vis-NIR broad spectrum was realized for the first time. The presence of surface oxygen vacancy defects on Bi2WO6 resulted in significant photocatalytic enhancement over the pristine counterpart under UV and visible light irradiation. Meanwhile, the photocatalytic responsiveness of Bi2WO6-OV was successfully extended to the NIR region.