Hierarchical SnO2 hollow sub-microspheres for panchromatic PbS quantum dot-sensitized solar cells

In contrast with the commonly used TiO2 or ZnO electron transporters, SnO2, which possesses relatively low conduction band and high electron-mobility, is expected to facilitate the extraction of photogenerated electrons from quantum dots (QDs) to oxides in quantum dot-sensitized solar cells (QDSCs), especially for those narrow band gap QDs (e.g., PbS). In this work, hierarchical SnO2 hollow sub-microspheres have been synthesized by a facile one-step hydrothermal process, and further studied for near infrared responsive PbS QDSCs. Morphology and structure characterizations reveal that these sub-micrometer-sized spheres (150-200 nm) with hollow interiors are assembled by numerous packed nanograins. The nanometer-sized grains ensure large specific surface area (∼69.2 m2 g−1) and pore size (∼19 nm) for high QD loading, while the sub-micrometer-sized spheres function as efficient light scatters and robust electron transporting structures. As a result, these superior features make such hierarchical SnO2 architectures very promising candidates for photovoltaic application. Based on the multifunctional photoelectrode constructed with hierarchical SnO2 hollow architectures, an appreciable power conversion efficiency up to 1.34% has been achieved for a PbS QDSC, coupled with interface engineering through TiO2 coating and CdS passivation. This work offers a promising design for developing high performance QDSCs.