Synthesis of indium phosphide for thin film solar cells

Research was articulated in several branches; initially direct indium phosphide deposition in aqueous solutions was investigated, this was performed on different substrates starting from inorganic indium and phosphorus precursors. InP could not be obtained with this process but oxidized forms of phosphorus were deposited together with indium. Consequently indium and red phosphorous composite deposition was studied due to negative results from direct deposition. This was performed on Molybdenum substrates, starting from a suspension of red phosphorus in aqueous baths containing In3+. Just partial reaction of In with Pred was possible after annealing, leading to compositional inhomogeneity in the deposit. Pure indium deposition followed by phosphorous incorporation was then considered, studies were performed both on the pure indium plating step and on the following incorporation technique. Two different processes were used and studied: phosphorization of the In layer in phosphine gas and dropcasting of red phosphorous on indium followed by thermal treatment. Phosphorization led to good quality InP as confirmed from compositional analysis and optical characterization (PL and TRPL): photoluminescence peak was found to be at the theoretical value for InP, 920nm, and exciton lifetime resulted to be 2,3ns from time resolved photoluminescence. The dropcasting process is promising but still needs some improvements since partial conversion of In to InP was obtained. For the solutions used during deposition, cyclic voltammetry was performed in parallel with plating, in order to characterize precursors and determine the effect of additions to the solution. The script is organized into different parts: in the first part (chapter 1) is reported an overview on solar photovoltaic, electrodeposition and the state of the art about InP. In the second part (chapter 2) experimental procedure is defined and results are reported (chapter 3), finally discussion of experimental results is performed (chapter 4).