Dilute nitride Ⅲ-Ⅴ nanowires for high-efficiency intermediate-band photovoltaic cells: Materials requirements, self-assembly methods and properties

摘要

This paper deals with dilute nitride Ⅲ-Ⅴ (Ⅲ-N-Ⅴ) semiconductor nanowires and their synthesis by bottom-up (so-called self-assembly) methods for application to novel and high efficiency intermediate-band solar cells (IBSCs). Nanowire-IBSCs based on III-N-V compounds promise to overcome many of the limitations encountered so far in quantum-dots or planar-heterostructure IBSCs; indeed, thanks to the combination of IBSC functionality with the unique physical properties associated with nanowires-based devices, photovoltaic cells with unprecedentedly high power conversion efficiency, simpler junction geometry, reduced structural constraints, low materials usage and fabrication costs could be conceived. The fabrication of Ⅲ-N-Ⅴ nanowire-IBSCs requires however, careful engineering of the inner nanowire-device structures to comply with both IBSC stringent operational requirements and the peculiar physical properties of Ⅲ-N-Ⅴ semiconductor alloys. Herewith, we propose for the first time perspective Ⅲ-N-Ⅴ core-multishell nanowire heterostructures as potential candidates to IBSC applications, their fabrication requiring however, precisely controlled self-assembly technologies. The present status of research on the topic is reviewed, focusing in particular on the bottom-up growth of Ⅲ-N-Ⅴ nanowires by molecular beam and metalorganic vapor phase epitaxy methods and properties of as-grown nanostructures. Major results achieved in the current literature and open problems are presented and discussed, along with advantages and limitations of employed self-assembly methods for the fabrication of dilute nitride Ⅲ-Ⅴ based nanowire-IBSCs.