Characterization of ZnO films obtained by ultrasonic spray pyrolysis technique Bengisu Ergin, Elif Ketenci, Ferhunde Atay* Eskisehir Osmangazi University, Physics Department, 26480 Eskisehir, Turkey article info Article history: Received 1 September 2008 Accepted 24 September 2008 Available online 11 December 2008 Keywords: ZnO Ultrasonic spray pyrolysis Electrical and optical properties XRD SEM EDS abstract In this work, ZnO film was deposited onto microscope glass substrates at 300  5  C by ultrasonic spray pyrolysis technique to investigate its application potential in photovoltaic solar cells. Optical, surface, structural and electrical properties of the film were investi- gated. Transmittance and absorbance spectra were taken to examine the optical proper- ties, and band gap was calculated by optical method. Scanning electron microscopy micrographs and X-ray diffraction pattern were used to investigate the surface and structural properties of the film, respectively. Temperature dependent current measure- ments were performed by two-probe method to analyze electrical properties, and electrical conductivity at room temperature and activation energy values were calculated. After all investigations, application potential of ZnO film in photovoltaic cells as transparent con- ducting oxide contact was searched. ª 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. 1. Introduction ZnO, which belongs to II–VI compound semiconductors, has been under extensive research in recent years for its wide technological applications [1]. It shows high electrical conductivity by doping with suitable elements [2,3]. ZnO is optically transparent in visible region and its band gap energy is relatively wide [4]. Recently, it has attracted much more interest in application of opto-electronic devices [5–8]. It has piezoelectric properties, high transparency, good conductivity and chemical and mechanical stability [9–14]. ZnO and ZnO- doped films are starting to be used as transparent conducting coatings in liquid crystal displays and solar cells [15]. ZnO can be produced by several techniques such as chemical vapour deposition [10,13,16,17], spray pyrolysis [14], sputtering [12], sol-gel process [18,19] and laser ablation [11]. Among these techniques, spray pyrolysis competes with the others due its low cost and suitable properties [20], and this technique is a process well suited to large-scale production [21,22]. In this work, the optical, morphological, structural and electrical properties of ZnO film produced by ultrasonic spray pyrolysis technique were reported, and the application potential of the film for solar cell devices as transparent conducting oxide contact was searched. 2. Experimental procedure ZnO film was deposited by ultrasonic spray pyrolysis (USP) technique. Our schematic diagram of the USP set-up is shown in Fig. 1. Zn(CH 3 COO) 2 $2H 2 O liquid solution (0.1 M) was used as starting spraying solution. ZnO film was produced at a substrate temperature of 300  5  C, and the substrate temperature was measured using an iron–constantan ther- mocouple. Totally 100 cc of solution was sprayed onto pyrex * Corresponding author. Tel.: þ90 222 2393750/2825; fax: þ90 222 2393578. E-mail addresses: best_bengg@hotmail.com (B. Ergin), ekentenci@ogu.edu.tr (E. Ketenci), fatay@ogu.edu.tr (F. Atay). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he 0360-3199/$ – see front matter ª 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2008.09.108 international journal of hydrogen energy 34 (2009) 5249–5254