Hole-induced large-area homoepitaxial growth of CdSe nanowire arrays for photovoltaic application

Traditionally, lattice-matched substrates are a requisite for the epitaxial growth of one-dimensional (1D) semiconductor nanostructure arrays, while the lack of suitable substrates seriously limits the nanowire (NW) arrays available for future nanoelectronic and nano-optoelectronics applications. In this work, we reported a new strategy for achieving the one-step homoepitaxial growth of highly aligned CdSe NW arrays by utilizing porous silicon as substrates. The porous Si with dense holes could promote the nucleation of CdSe micro-crystals at the early stage of vapor phase transport owing to its high surface energy. Subsequently, the epitaxial growth of CdSe NW arrays would take place on the top surfaces of the micro-crystals, resulting in large-area highly aligned NW arrays. As compared with the conventional epitaxial methods, the hole-induced method is greatly simplified because no lattice-matched substrates or catalysts are needed; furthermore, the universality of the proposed method was demonstrated for a variety of II-VI NW arrays. As a demonstration of the potential applications, preliminary studies on CdSe NW array/Si p-n heterojunction solar cells were shown with an efficiency of similar to 0.43% under AM 1.5G illumination.