1 Substrate -Nozzle Distance (SND) influence on the Properties of Fluorine-Doped Tin Oxide Thin Films Ayodeji Oladiran Awodugba Department of Pure and Applied Physics, Ladoke Akintola University of Technology, Ogbomoso aoawodugba@lautech.edu.ng Corresponding author Gbadebo Taofeek Yusuf Department of Science Laboratory Technology, Physics Unit, Osun State Polytechnic, Iree taofeeky001@gmail.com Abstract This work examines the impact of the nozzle-substrate distance (NSD) on the structural, optical and electrical properties of fluorine-doped tin oxide (FTO) thin films. The films were grown by spray pyrolysis with the chemical formulation of “Streaming Process for Electroless and Electrochemical Deposition technology” (SPEED) technique. The characterization technique such as XRD, SEM, UV-spectrophotometry and Hall Effect measurement were employed for studying the structural, optical and electrical properties of the FTO films at various NSD. The NSD was varied from 25- 32cm amid the experiment. All FTO films are polycrystalline, tetragonal crystal structure with strong orientation along the (211) reflection. SEM properties study demonstrated slight reliance on NSD and have uniform films which are a disciple to substrate at NSD of 27 and 30 cm, however, crumbled at 25cm and 32cm NSD. They likewise displayed a mud-look like morphology and smooth white appearance. The average optical transmittance of all films is over 80% in the noticeable at UV range. The band gap investigation demonstrates the average value of 3.5eV and the resistivity was found to diminish with increasing NSD at 30 cm. Both mobility and carrier concentration of the FTO films follow a similar trend. The average figure of merit of 4.98 × 10    was obtained which is an improvement based on our previous results. The FTO samples grown at 27 and 30 cm NSD in this work are best FTO samples and hence could serve as a promising candidate in dye sensitized solar cells. Therfore, graphene has been employed in different concentrations in our ongoing FTO optimization research so as to further improve on the FTO’s figure of merit. Keywords: NSD, Fluorine, morphology, SPEED 1. Introduction Among the transparent conducting oxides, fluorine-doped tin oxide (FTO) is the best material that could replace indium tin oxide (ITO) which is expensive due to the scarcity of element “indium” present in the compound [1]. It is an n-type, wide band gap semiconductor, with an average band gap of 3.5 eV and with special properties such as high transmittance in the visible range and high reflectance in the infrared, high carrier mobility, excellent electrical conductivity, and good stability at higher temperature [2]. FTO has a lot of applications which include: solar cells, protective electrodes, flat panel collectors, sensors, sodium lamps, and varistors. The microstructural, electrical and optical properties of FTO are sensitive to deposition techniques and conditions [3]. Extensive research has been focused so far on finding a way to overcome problems associated with FTO thin films through methods of fabrication and growth control [4-7]. The effect of several technological parameters such as doping concentration, solvent, substrate temperature, etc. on the properties of sprayed FTO films has been studied to determine the optimal deposition conditions to obtain as high electrical conductivity and optical transparency as possible [4-7].Numerous methods have been used for deposition of fluorine-doped thin films such as Thermal Evaporation [4, 9], Spray Pyrolysis [4, Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 7 December 2017 doi:10.20944/preprints201712.0043.v1 © 2017 by the author(s). Distributed under a Creative Commons CC BY license.