Solar Energy 211 (2020) 1017–1026 Available online 22 October 2020 0038-092X/© 2020 International Solar Energy Society. Published by Elsevier Ltd. All rights reserved. Fluorine-free synthesis of reduced graphene oxide modifed anatase TiO 2 nanofowers photoanode with highly exposed {0 0 1} facets for high performance dye-sensitized solar cell N. Pugazhenthiran a, b, * , R.V. Mangalaraja b, * , S. Vijaya c , S. Suresh d , M. Kandasamy e , P. Sathishkumar f , H. Vald´ es a , M.A. Gracia-Pinilla g , S. Murugesan e , S. Anandan c a Clean Technologies Laboratory, Engineering Faculty, Universidad Cat´ olica de la Santísima Concepci´ on, Alonso de Ribera 2850, Concepci´ on, Chile b Advanced Ceramics and Nanotechnology Laboratory, Department of Materials Engineering, Faculty of Engineering, University of Concepcion, Concepcion 4070409, Chile c Nanomaterials and Solar Energy Conversion Lab, Department of Chemistry, National Institute of Technology, Trichy 620 015, India d PG & Research Department of Physics, Sri Vidya Mandir Arts & Science College (Autonomous), Katteri 636 902, Uthangarai, Tamil Nadu, India e Department of Inorganic Chemistry, School of Chemistry, Madurai Kamaraj University, Madurai 625 021, Tamil Nadu, India f Department of Chemistry, School of Advanced Sciences, Vellore Institute of Technology (VIT), Vellore 632 014, Tamil Nadu, India g Universidad Autonoma de Nuevo Leon, Facultad de Ciencias Físico-Matematicas, Av. Universidad, Cd. Universitaria, San Nicolas de los Garza, N.L., Mexico A R T I C L E INFO Keywords: TiO 2 nanofowers {0 0 1} facets Reduced graphene oxide Dye-sensitized solar cell Photovoltaic performance ABSTRACT A facile, fuorine-free and non-toxic one-pot solvothermal technique was adopted to synthesis TiO 2 nanofowers with anatase phase having 98% highly exposed {0 0 1} facets (TiO 2 {0 0 1} NFs). The morphology, grain size and crystallinity of pure TiO 2 {0 0 1} NFs and reduced graphene oxide (RGO) sheets modifed TiO 2 {0 0 1} NFs (RGO- TiO 2 {0 0 1} NFs) were inspected by diffuse refectance spectroscopy (DRS), X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM images showed the development of anatase TiO 2 {0 0 1} NFs with high crys- tallinity and uniform shape. The infuence of RGO on the performance of the TiO 2 {0 0 1} NFs as a photoanode material in dye-sensitized solar cell (DSSC) was examined. High energy conversion effciency (ɳ) was observed for the DSSC based on a photoanode made of RGO-TiO 2 {0 0 1} NFs when compared to DSSCs based on pho- toanodes fabricated using pure TiO 2 {0 0 1} NFs and commercial Degussa P25 TiO 2 , which exhibited η of 6.78, 4.59 and 2.71%, respectively. The improved performance of the DSSC based on a photoanode composed of RGO- TiO 2 {0 0 1} NFs was due to its good crystallinity, high dye intake and enhanced light-harvesting properties. Moreover, the presence of RGO greatly hindered the recombination of photogenerated electrons and increased their lifespan. This work discloses a novel effcient photoanode design for improving performance of the DSSCs. 1. Introduction Dye-sensitized solar cells (DSSCs) have gained enormous scientifc and technological research attention in last two decades, because of their credible features of reliable energy transformation, economical fabrication, eco-friendly and multicolor options (Hagfeldt et al., 2010; O’Regan and Gr¨ atzel, 1991; Yella et al., 2011). A standard DSSC struc- ture is comprised of a nanocrystalline semiconductor thin flm photo- anode formed on a transparent conducting glass substrate, a dye sensitizer, an iodide/tri-iodide redox liquid electrolyte and a platinum deposited counter electrode (Yanagida et al., 2009; Hardin et al., 2012). Among them, the photoanode has the capability of chiefy infuencing overall performance of the DSSC which performs as scaffolds for dye molecules and it is responsible for photovoltage and photocurrent as a transport medium and separation of photo-generated charge carriers (Crossland et al., 2013; Wu et al., 2014; Lan et al., 2016). Titanium dioxide (TiO 2 ) has been documented to be widely chosen photoanode material in DSSC, as it has profcient optical, physical and chemical properties, low-toxicity and favorable bandgap energy (Lee et al., 2014; Li et al., 2014). The performance of TiO 2 in DSSC pro- foundly relies on its morphology, crystalline phase and structure as well as in its exposed crystal facets (Liao et al., 2011; Park et al., 2000; Chen * Corresponding authors. E-mail addresses: pugazhenthiran@ucsc.cl (N. Pugazhenthiran), mangal@udec.cl (R.V. Mangalaraja). Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener https://doi.org/10.1016/j.solener.2020.10.008 Received 18 August 2020; Received in revised form 28 September 2020; Accepted 5 October 2020