Atmospheric pressure synthesis of In 2 Se 3 , Cu 2 Se, and CuInSe 2 without external selenization from solution precursors Jennifer A. Nekuda Malik a) Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401; and National Renewable Energy Laboratory, Golden, Colorado 80401 Maikel F.A.M. van Hest, Alexander Miedaner, Calvin J. Curtis, Jennifer E. Leisch, and Philip A. Parilla National Renewable Energy Laboratory, Golden, Colorado 80401 Michael Kaufman Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401 Matthew Taylor and B.J. Stanbery HelioVolt Corporation, Austin, Texas 78744 Ryan P. O’Hayre Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, Colorado 80401 David S. Ginley b) National Renewable Energy Laboratory, Golden, Colorado 80401 (Received 2 June 2008; accepted 24 November 2008) In 2 Se 3 , Cu 2 Se, and CuInSe 2 thin films have been successfully fabricated using novel metal organic decomposition (MOD) precursors and atmospheric pressure-based deposition and processing. The phase evolution of the binary (In-Se and Cu-Se) and ternary (Cu-In-Se) MOD precursor films was examined during processing to evaluate the nature of the phase and composition changes. The In-Se binary precursor exhibits two specific phase regimes: (i) a cubic-In x Se y phase at processing temperatures between 300 and 400  C and (ii) the g-In 2 Se 3 phase for films annealed above 450  C. Both phases exhibit a composition of 40 at.% indium and 60 at.% selenium. The binary Cu-Se precursor films show more diverse phase behavior, and within a narrow temperature processing range a number of Cu-Se phases, including CuSe 2 , CuSe, and Cu 2 Se, can be produced and stabilized. The ternary Cu-In-Se precursor can be used to produce relatively dense CuInSe 2 films at temperatures between 300 and 500  C. Layering the binary precursors together has provided an approach to producing CuInSe 2 thin films; however, the morphology of the layered binary structure exhibits a significant degree of porosity. An alternative method of layering was explored where the Cu-Se binary was layered on top of an existing indium-gallium-selenide layer and processed. This method produced highly dense and large-grained (>3 mm) CuInSe 2 thin films. This method has significant potential as a manufacturable route to CIGS-based solar cells. I. INTRODUCTION Copper indium diselenide (CuInSe 2 , CIS) and its related gallium-substituted alloy (CIGS) solar cells are among the most promising thin-film photovoltaic technologies, with demonstrated laboratory efficiencies of more than 14% for pure CIS 1 and nearly 20% for CIGS. 2,3 However, historically the ability to expand CuInSe 2 (CIS) cells to the energy production market has been hindered by the deposition and processing methods used to produce CIS solar cells. Common CIS fabrication methods use physical vapor deposition in ultra-high vacuum chambers 4 and/or the use of highly toxic substances like H 2 Se and Se 2 for selenization. 5–7 Due to issues concerning capi- talization, scalability, materials utilization, and energy intensity of these methods, there is great interest in pur- suing alternative and potentially more manufacturable fabrication methods. Address all correspondence to these authors. a) e-mail: jnekuda@gmail.com b) e-mail: david_ginley@nrel.gov This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs.org/jmr_policy DOI: 10.1557/JMR.2009.0155 J. Mater. Res., Vol. 24, No. 4, Apr 2009 © 2009 Materials Research Society 1375