Photovoltaic conversion using Zn chlorophyll derivative assembled in hydrophobic domain onto nanocrystalline TiO2 electrode

Photovoltaic conversion using zinc chlorin-e(6) (ZnChl-e(6)), which is zinc chlorophyll-a derivative, and fatty acid (myristic acid or cholic acid) co-adsorbed nanocrystalline TiO2 layer onto ITO glass (OTE) electrode is developed. The maximum peaks of photocurrent action spectrum of the ZnChl-e(6) adsorbed TiO2 layer onto OTE (ZnChl-e(6)/TiO2) are 400, 660 and 800 nm, respectively. Especially the IPCE value at 800 nm (7.5%) is larger than that of 660 nm (6.9%). This result indicates that ZnChl-e(6) molecules is aggregated or formed dimer on a nanocrystalline TiO2 layer onto OTE and the absorption band is shifted to near IR region. The photocurrent action spectrum of ZnChl-e(6) and cholic acid adsorbed TiO2 layer onto OTE (ZnChl-e(6)-Cho/TiO2) is similar to that of the UV-vis absorption spectrum in methanol solution, and IPCE values at 400 and 660 nm (8.1%) increase and the IPCE value at 800 nm (4.1%) decreases, indicating that the aggregation of ZnChl-e(6) Molecules on the TiO2 is suppressed by cholic acid. By using ZnChl-e(6)-Cho/TiO2, the short-circuit photocurrent density and open-circuit photovoltage also increase compared with that of ZnChl-e(6) adsorbed nanocrystalline TiO2 electrode. (c) 2006 Elsevier B.V. All rights reserved.