Delivered by Publishing Technology to: Chinese University of Hong Kong IP: 117.253.107.177 On: Mon, 22 Feb 2016 20:02:18 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2011 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 11, 3560–3564, 2011 Growth of Aligned Hexagonal ZnO Nanorods on FTO Substrate for Dye-Sensitized Solar Cells (DSSCs) Application Ahmad Umar 1 ∗ , A. A. Alharbi 2 , Pragya Singh 3 , and S. A. Al-Sayari 1 1 Advanced Materials and Nano-Engineering Laboratory (AMNEL), Centre for Advanced Materials and Nano-Engineering (CAMNE), Najran University, P. O. Box 1988, Najran, 11001, Kingdom of Saudi Arabia 2 Solid State Research Group, King Abdulaziz City for Science and Technology, KACST, P. O. Box 6086, Riyadh 11442, Saudi Arabia 3 Department of Electronics and Communication Engineering, Meerut Institute of Engineering and Technology, Meerut 250005, India This article reports a facile growth of well-crystalline aligned hexagonal ZnO nanorods on fluorine- doped tin-oxide (FTO) substrate via non-catalytic thermal evaporation process. The morphologi- cal investigations done by field-emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) reveal that the grown products are aligned hexagonal ZnO nanorods which are grown in a very high density over the whole substrate surface. The detailed structural properties observed by high-resolution TEM equipped with selected area electron diffraction (SAED) and X-ray diffraction (XRD) pattern confirmed that the synthesized nanorods are well-crystalline possessing wurtzite hexagonal phase and preferentially grown along the c-axis direction. A sharp and strong UV emission at 381 nm in room-temperature photoluminescence (PL) spectrum showed that the as-grown ZnO nanorods possess excellent optical properties. The as-grown nanorods were used as photo-anode for the fabrication of dye-sensitized solar cells (DSSCs) which exhibits an over- all light-to-electricity conversion efficiency (ECE) of 0.7% with V OC of 0.571 V, J SC of 2.02 mA/cm 2 and FF of 0.58. Keywords: Aligned Hexagonal ZnO Nanorods, Structural Characterization, Optical Properties, Dye-Sensitized Solar Cells. 1. INTRODUCTION Due to the increasing demand of energy, a substantial progress has been made in the search and development of new and renewable energy sources. Among various renewable energy technologies, the solar energy is con- sidered to be the most important energy source due to their environmental benign (carbon-neutral) nature. Along with different solar energy technologies, the dye sen- sitized solar cells (DSSCs) have received considerable attention because of their reasonable efficiency, simple fabrication and cost effective alternative to silicon solar cells. 1 2 Up to now, nanocrystalline TiO 2 were widely used as photoanode material for the fabrication of DSSCs and reported in the literature. 1–4 Recently, other wide band-gap semiconductor nanostructures are also utilized ∗ Author to whom correspondence should be addressed. as photoanode materials for DSSCs fabrication. 1 2 Among different semiconductor nanostructures, the II–VI wide band gap semiconductor, ZnO presents itself as an effi- cient material which is expected to be compatible with TiO 2 as an photoanode material due to its higher elec- tronic mobility, similar electron affinity and band gap (3.37 eV at 298 K). 1 2 In addition to this, ZnO exhibiting various other exotic properties which are highly suitable for the fabrication of various high-efficient devices. The properties of ZnO include its direct and wide band gap (3.37 eV), large exciton binding energy (60 meV), high optical gain of 300 cm -1 (100 cm -1 for GaN) at room temperature, large saturation velocity (32 × 10 7 cm/s) and so on. In this regard, variety of ZnO nanostructures, such as nanorods, 5 nanowires, 4 nanoflowers, 6 nanocombs, 7 nanosheets, 8 nanoflakes 9 etc. have been synthesized and utilized as photoanode for the fabrication of efficient 3560 J. Nanosci. Nanotechnol. 2011, Vol. 11, No. 4 1533-4880/2011/11/3560/005 doi:10.1166/jnn.2011.4150