Quaternary ammonium polyiodides as ionic liquid/soft solid electrolytes in dye-sensitized solar cells

Four new quaternary ammonium iodides, (Me(2)PeN)I, (Me(2)Hex(2)N)I, (Et(2)Pe(2)N)I and (Et(2)Hex(2)N)I, were synthesized and studied as electrolytes in dye-sensitized solar cells. All compounds were solids at room temperature. Influence of varying amounts of elemental iodine and the effect of tertbutylpyridine (TBP) on the performance of the cell was also studied. Addition of iodine lowered the melting points of the resulting polyiodides. From the ammonium iodides only (Me(2)Hex(2)N)O:I-2 (10:1) was liquid at the room temperature and the others were soft solids. Under illumination from a halogen lamp source at 10 mW cm(-2) intensity, the highest power conversion efficiency of 2.4% was obtained with the (Me(2)Hex(2)N)I:I-2 (10:1) liquid electrolyte containing TBP, which may be compared to an efficiency of 5.4% obtained from similar cells with traditional 3-methoxypropionitrile based electrolyte tested under identical conditions. The best efficiency with soft solid electrolyte, (Et(2)Hex(2)N)I:I-2 (10:1) with TBP, was 2.3%. (c) 2006 Elsevier B.V. All rights reserved.