Hindawi Publishing Corporation International Journal of Chemical Engineering Volume 2011, Article ID 545234, 8 pages doi:10.1155/2011/545234 Research Article A Large-Scale Synthesis and Characterization of Quaternary CuIn x Ga 1−x S 2 Chalcopyrite Nanoparticles via Microwave Batch Reactions Chivin Sun, 1 Richard D. Westover, 1 Gary Long, 1 Cyril Bajracharya, 1 Jerry D. Harris, 2 Alex Punnoose, 3 Rene G. Rodriguez, 1 and Joshua J. Pak 1 1 Department of Chemistry, Idaho State University, Pocatello, ID 83209, USA 2 Department of Chemistry, Northwest Nazarene University, Nampa, ID 83686, USA 3 Department of Physics, Boise State University, Boise, ID 83725, USA Correspondence should be addressed to Joshua J. Pak, pakjosh@isu.edu Received 29 March 2011; Accepted 9 August 2011 Academic Editor: Deepak Kunzru Copyright © 2011 Chivin Sun et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Various quaternary CuIn x Ga 1−x S 2 (0 ≤ x ≤ 1) chalcopyrite nanoparticles have been prepared from molecular single-source precursors via microwave decomposition. We were able to control the nanoparticle size, phase, stoichiometry, and solubility. Depending on the choice of surface modifiers used, we were able to tune the solubility of the resulting nanoparticles. This method has been used to generate up to 5 g of nanoparticles and up to 150 g from multiple batch reactions with excellent reproducibility. Data from UV-Vis, photoluminescence, X-ray diffraction, TEM, DSC/TGA-MS, and ICP-OES analyses have shown high reproducibility in nanoparticle size, composition, and bandgap. 1. Introduction For nearly three decades, chalcopyrite CuIn 0.7 Ga 0.3 Se 2 (CIGS) and related materials have attracted much interest due to their potential applications in photovoltaic and other optoelectric devices [1–5]. Many thin film PV devices of CIGS set respectable power conversion efficiency of about 20% [6, 7]. In recent years, there have been increasing reports on using colloidal I–III–VI nanoparticle suspensions, com- posites, and inks to prepare PV devices. Solution processing strategies such as spin coating [8–10] and ink printing [1, 2, 4] are being explored for large areas of CIGS while lowering the overall costs. One of the key stoichiometric requirements is to consis- tently maintain In/Ga ratio to 0.7/0.3 from batch to batch. Previously, we reported the efficient syntheses of quaternary CuIn x Ga 1−x S 2 (0 ≤ x ≤ 1) chalcopyrite nanoparticles with precise stoichiometric control by decomposition of a mixture of two I–III bimetallic single-source precursors (SSPs), (Ph 3 P) 2 Cu(μ-SEt) 2 In(SEt) 2 (1), and (Ph 3 P) 2 Cu(μ- SEt) 2 Ga(SEt) 2 (2), in the presence of 1,2-ethanedithiol via microwave irradiation [11]. Use of SSPs in preparation of nanomaterials presents distinct advantages such as precise control of reaction con- ditions and stoichiometry as SSPs contain all necessary ele- ments in a single molecule. Despite the obvious advantages of SSPs, to our knowledge, no studies have been conducted using combinations of SSPs to form soluble and insoluble ternary and quaternary chalcopyrite nanoparticles. Microwave-assisted preparation of nanoparticles from SSPs offers advantages over traditional thermolysis as micro- wave provides rapid heating as well as greater homogeneity in the overall reaction temperature [12]. This usually allows for the preparation of nanoparticles with increased size control [13], dramatic decreases in reaction times, improved product purities, and reactions exhibiting good reproducibility and high yields [14, 15].