A  oriented hybrid 3D ZnO nanowall architecture with enhanced dye-sensitized solar cell performance†
Orientation and morphology of metal-oxide nanomaterials have a major impact on their properties and applications. Here, we developed a hybrid 3D ZnO nanowall (NWL) architecture on a FTO glass substrate via a low-temperature solution process. The as grown hybrid 3D ZnO NWL architecture is a perfect single crystal with a wurtzite structure, and its orientation along the  direction is confirmed using transmission electron microscopy. Such an architecture has a unique combination of a high surface-area with cage-like pores, which was applied as an electron transporting material (ETM) in porphyrin-based dye-sensitized solar cells. These devices exhibited a maximum photocurrent density of 11.86 mA cm−2, a power conversion efficiency of 4.08%, which was higher than those of pristine ZnO nanowall (2.76%) and nanowire (1.92%) devices; due to their surface area and orientation. Their orientation and surface area led to a faster charge transport rate than those of the ZnO mesoporous films and the  oriented ZnO nanostructure. The unique crystallographic orientation of the 3D ZnO NWL architecture opens up a novel configuration for designing high-performance optoelectronic devices and expands their application fields.