Solution-derived 40 µm vertically aligned ZnO nanowire arrays as photoelectrodes in dye-sensitized solarcells

Abstract

Well-aligned ZnO nanowire arrays with a long length of more than 40 µm were prepared successfully by using the polyethylenimine (PEI)-assisted preheatinghydrothermal method (PAPHT). Several important synthetic parameters such as PEIcontent, growth time, preheating time and zinc salt concentration were found to determinethe growth of ultralong ZnO nanowire arrays, including length, diameter, density andalignment degree. The photoluminescence (PL) spectrum of as-grown ultralong ZnOnanowire arrays revealed a UV emission and a yellow emission, which was attributed to theabsorbed hydroxyl group based on the peak shift after annealing in various atmospheres.The performance of dye-sensitized solar cells (DSSCs) increased with increasing length ofZnO nanowire arrays, which was mainly ascribed to the aggrandized photocurrent andreduced recombination loss according to electrochemical impedance spectroscopy(EIS). A maximum efficiency of 1.3% for a cell with a short-circuit current density(Jsc) = 4.26 mA cm2, open-circuit voltage(Voc) = 0.69 V and (fill factor)FF = 0.42 was achieved witha length of 40 µm.