Photoelectron spectroscopy studies of Ru(dcbpyH2)2(NCS)2/CuI and Ru(dcbpyH2)2(NCS)2/CuSCN interfaces for solar cell applications

In this work, the electronic structure of the wide band gap hole conductors Cut and CuSCN in contact with an organic dye (Ru(dcbpyH(2))(2)(NCS)(2), cis-bis(4,4'-dicarboxy-2,2-bipyridine)bis(isothiocyanato)ruthenium(II)) were investigated by means of photoelectron spectroscopy. The experiments show specific interaction between the NCS groups of the dye molecules and the Cut and CuSCN surfaces. For Cut there are strong indications that the dye molecules interact with Cut through both NCS ligands. Also, one of the carboxylic groups is affected by the surface adsorption on the CuI substrate. For the CuSCN surface the results indicate that about half of the molecules interact with the surface through both NCS ligands, that about half of the molecules interact with the surface through one NCS ligand, and that there is no specific interaction with the carboxylic groups. The measurements also reveal changes in the electronic structure of the dye molecule when adsorbed onto the substrates. In particular, changes in the upper valence electronic structure, important for the function of this material combination in a solar cell device, are discussed.