Solar Energy Materials & Solar Cells 75 (2003) 145–153 Preparation of CuIn 1Àx Ga x Se 2 thin films by sputtering and selenization process Ho Keun Song a,n ,SooGilKim a , Hyeong Joon Kim a ,Suk KiKim b ,KiWanKang b ,JungChulLee b ,KyungHoonYoon b a School of Materials Science and Engineering, Seoul National University, 151-742 Seoul, South Korea b New energy Department, Korea Institute of Energy Research, Taejon, 305-343, South Korea Abstract CuIn 1Àx Ga x Se 2 polycrystalline thin films were prepared by a two-step method. The metal precursors were deposited either sequentially or simultaneously using Cu–Ga (23at%) alloy andIntargetsbyDCmagnetronsputtering.TheCu–In–Gaalloyprecursorwasdepositedon glass or on Mo/glass substrates at either room temperature or 1501C. These metallic precursorswerethenselenizedwithSepelletsinavacuumfurnace.TheCuIn 1Àx Ga x Se 2 films had a smooth surface morphology and a single chalcopyrite phase. r 2002 Elsevier Science B.V. All rights reserved. Keywords: CuIn 1Àx Ga x Se 2 ; Two-step method; DC magnetron sputtering; Selenization 1. Introduction CuIn 1Àx Ga x Se 2 polycrystalline thin films have been considered as an effective absorbermaterialforhighlyefficientsolarcells.Variousmethodshavebeencarried outtoprepareCuInSe 2 (CIS)-basedsolarcellthinfilm,includingtheselenizationof sputteredmetalfilm[1–3],co-evaporation[4,5],molecularbeamdeposition[6,7],and spray pyrolysis [8,9]. Solar efficiencies of over 18% have been reported for the CuIn 1Àx Ga x Se 2 solarcellspreparedbyco-evaporationoftheelementalsources(Cu, In, Ga, and Se) through a three-stage process [10]. However, this method has a difficultytobescaledupforalarge-manufacturingsystemduetoitscomplexity.On the other hand, a two-step process, in which the selenization step follows the sputtering step of the metallic precursors, has many advantages in industrial applications compared to the three-stage process. n Corresponding author. 0927-0248/03/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0927-0248(02)00125-3