Preparation of indium sulfide thin films by spray pyrolysis using a new precursor indium nitrate Teny Theresa John a , C. Sudha Kartha a , K.P. Vijayakumar a, * , T. Abe b , Y. Kashiwaba b a Thin Film Photovoltaic Division, Department of Physics, Cochin University of Science and Technology, Kochi 682022, India b Department of Electrical and Electronic Engineering, Iwate University, Morioka 020-8551, Japan Received 2 June 2004; received in revised form 17 December 2004; accepted 17 February 2005 Available online 31 March 2005 Abstract Indium nitrate and thiourea were used as the precursor solutions for preparing indium sulfide thin films using Chemical Spray Pyrolysis (CSP) technique. Films having various In/S ratios were characterized using X-Ray Diffraction (XRD), Energy Dispersive X-ray Analysis (EDX), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), optical absorption, transmission and photosensitivity measurements. Sample having In/S ratio 2/3 showed better crystallinity with band gap 2.66 eV. Depth profile of the sample also indicated the formation of indium sulfide. It was also observed that In/S ratio in the initial precursor solution determined the composition as well as electrical properties of the films. Maximum photosensitivity was observed for the sample prepared using solution having In/S ratio 2/4. # 2005 Elsevier B.V. All rights reserved. PACS: 81.15.Rs; 82.45.Mp Keywords: In 2 S 3 ; Indium nitrate; Chemical spray pyrolysis; In/S ratio 1. Introduction Thin film solar cells based on Cu(In, Ga)Se 2 , CuInSe 2 and CuInS 2 absorber layers showed promising solar energy conversion efficiencies (>10%) [1–3] using CdS as buffer layer. But presently efforts are there for replacing CdS layer by indium sulfide thin films to avoid toxic cadmium in order to make more ecofriendly photovoltaic technology. Efficiency up to 15.7% was achieved with chemical bath deposited In x (OH,S) y as buffer layer in CIGS based solar cells [4]. Moreover, being a wider band gap material than CdS, as a buffer layer, this material should decrease optical absorption losses at short wavelengths, leading to a gain in effi- ciency through a corresponding increase in short circuit current. Recently Nakada and Mizutani [5] showed that www.elsevier.com/locate/apsusc Applied Surface Science 252 (2005) 1360–1367 * Corresponding author. Tel.: +91 484 2577404; fax: +91 484 2577595. E-mail address: kpv@cusat.ac.in (K.P. Vijayakumar). 0169-4332/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2005.02.093