Metal and Semiconductor Nanowire Network Thin Films with Hierarchical Pore Structures

Abstract

Metal and semiconductor nanowire thin films with hierarchical pore structure were electrodeposited using mesoporous silica (primary porogens) containing colloidal silica particles (secondary porogens) as templates. The pore size of the nanowire thin films was independently controlled by the wall thickness of the surfactant-templated mesopores and the sizes of the incorporated silica particles. The mesostructure of the nanowire thin films (e.g., hexagonal and cubic mesostructures) was controlled by judicious choice of surfactant. Furthermore, the shape of the secondary pores (e.g., sphere and rod shapes) can be controlled using secondary porogens with various shapes. Such hierarchical nanowire thin films provide novel platforms for photovoltaic, sensor, and other device applications. To demonstrate the advantage of such hierarchical porous networks, we fabricated photovoltaic devices by infiltrating the hole-conducting poly(3-hexylthiophene) into the electron-conducting CdSe nanowire thin films with and without the secondary pore channels. The heterojunction solar cells consisting of a CdSe nanowire network with secondary pore structure and poly(3-hexylthiophene) showed improved performance with a short-circuit current of 2.4 mA/cm2 under AM 1.5 solar illumination, confirming the advantages of such hierarchical pore structure for actual device applications.