Dye-sensitized solar cells and complexes between pyridines and iodines. A NMR, IR and DFT study

Interactions between triiodide (I-3(-)) and 4-tert-butylpyridine (4TBP) as postulated in dye-sensitized solar cells (DSC) are investigated by means of C-13 NMR and IR spectroscopy supported by DFT calculations. The charge transfer (CT) complex 4TBP center dot I-2 and potential salts such as (4TBP)(2)I+, I-3(-) were synthesized and characterized by IR and C-13 NMR spectroscopy. However, mixing (butyl)(4)N+, I-3(-) and 4TBP at concentrations comparable to those of the DSC solar cell did not lead to any reaction. Neither CT complexes nor cationic species like (4TBP)(2)I+ were observed, judging from the C-13 NMR spectroscopic evidence. This questions the previously proposed formation of (4TBP)(2)I+ in DSC cells. (C) 2012 Elsevier B.V. All rights reserved.