LAUSR

Solar light can be captured by semiconducting particles and transformed into a fuel by inducing CO2 reduction and water decomposition. Thus appropriate semiconducting particles need to be identified and synthesized with appropriate and inexpensive processing. Ball milling is used in this investigation to synthesize CuInxGa(1-x)Se2 (CIGS) nanoparticles to capture solar light. Different intermediate stoichiometries are synthesized in order to completely determine the processing variables and conditions to achieve the main goal. CIGS is a family of semiconductors with a chalcopyrite crystalline structure and a variable bandgap that relates to the Ga-In relative contents from 1 for CuInSe2, (CIS) to about 1.7 eV for CuGaSe2, (CGS). Usually these materials are synthesized in thin films for solar cells and the corresponding composition must be kept within rather strict limits to avoid charge recombination. Nevertheless the use of nanoparticles in nanostructured devices can render sufficiently small distances to be traveled by the charges as to relax such a restriction. In the present investigation nanoparticles are produced with combinations of components of the CIGS materials by mechanical milling and starting from the corresponding chlorides in a dispersing excess of NaCl. X ray diffraction and electron microscopy are combined to characterize the resulting nanoparticles as a function of processing time (1 to 10 h) and chemical composition. Milling is done in a high energy device (Spex mill ®).