Fabrications and characteristics of ZnO nano-materials for efficient photovoltaic applications

Abstract

Nanostructured electronic devices are expected to facilitate the continuing miniaturization of electronic devices and enable ultra-low power device operation. In particular, one-dimensional (1D) nanostructures such as nanowire (NW) and nanotube have attracted great interest over the past decade because of their specific physical properties and their potential as building blocks for next-generation nano-electronic devices. Among various 1D materials, zinc oxide (ZnO), which has a direct and wide band gap, is a promising candidate for light-emitting diodes, UV/gas sensors, transistor channels, and other devices that can utilize the unique vertical alignment characteristics and highly ordered single crystalline properties of NW structures.Simple hybrid p-n homo-junctions using p-type ZnO thin films and n-type nanowires grown on fluorine tinoxide (FTO) substrates for photovoltaic applications are described. The ZnO nanwires (1.5 um) weresynthesized via ahydrothermal method with zinc nitrate hexahydrate and hexamethylenetetramineon ZnO seed layers. The 10 nm thick ZnO seed layers showed n-type conductivity on FTO substratesand were deposited with a sputtering-based method. After synthesizing ZnO nanowires, aluminum-nitrideco-doped p-type ZnO films (200 nm) were efficiently grown using pre-activated nitrogen (N) plasma sourceswith an inductively-coupled dual-target co-sputtering system. The structural and electrical properties ofhybrid p-n homo-junctions were investigated by scanning electron microscopy, transmittance spectrophotometry, and I?V measurements.