Hydrothermal Growth of Aligned ZnO Nanorods along the Seeds Prepared by Magnetron Sputtering and its Applications in Quantum Dots Sensitized Photovoltaic Cells

Abstract

Hydrothermal Growth of Aligned ZnO Nanorods along the Seeds Prepared by Magnetron Sputtering and its Applications in Quantum Dots Sensitized Photovoltaic Cells Well-aligned ZnO nanorods were grown on a conductive substrate via a hydrothermal route. The substrates were pre-seeded with ZnO by a technique of radio frequency (RF) magnetron sputtering. The influences of sputtering power, annealing treatment, and the size of seeds on the morphologies of the final-prepared ZnO nanorods have been studied. It was found that the length and the aspect ratio of the ZnO rods can be readily tuned by control of the ZnO seeds which results from the RF sputtering experiments. ZnO seeds deposited at low sputtering power (100~125 W) share uniform size distribution with smaller average size (~30 nm). Higher sputtering power yields longer ZnO rods with a higher aspect ratio up to ~12.5. The seed layers after annealing (~500ºC) produce ZnO rods with an increased average diameter and a smaller aspect ratio, and these features benefit the electron transfer when the prepared ZnO nano-arrays are used as electrode substrates in photovoltaic cells. By deposition of hydrophilic CdSe quantum dots (QDs) on the ZnO nano-rod, the maximum photo to current efficiency (0.42%) was obtained in case of ZnO nanorod with the length of ~2.75 μm and an aspect ratio of ~9.5 obtained from the seeds after annealing.