Potential applications of hierarchical branching nanowires in solar energy conversion

Nanoscience and nanotechnology can provide many benefits to photovoltaic and photoelectrochemical applications by combining novel nanoscale properties with processability and low cost. Taking advantage of high quality, high efficiency, yet low cost nanomaterials could potentially provide the new and transformative approaches to enable the proposed generation-III solar technologies. Nanowires are interesting because they have a long axis to absorb incident sunlight yet with a short radial distance to separate the photogenerated carriers. In this perspective, we further suggest that more "complex'' nanostructures, both in the form of hierarchically branching/hyperbranching nanowire structures and in the form of multi-component nanowire heterostructures of diverse materials, are potentially even more interesting for solar energy harvesting and conversion. The common bottom-up synthetic techniques to induce branching in nanowires to form hierarchical nanowire structures are reviewed. Several potential strategies for their incorporation into solar conversion devices are discussed and some fundamental issues and future directions are identified.