Investigation of use of zinc, cobalt and nickel phthalocyanines in dye sensitized solar cells

In this study, the peripherally tetra-substituted metallophthalocyanines (MPcs, M = Zn, Co, Ni) bearing the chalcone, (E)-3-(4-hydroxyphenyl)-1-(thiophen-2-yl)prop-2-en-1-one, for dye-sensitized solar cells (DSSCs) were used. Electrochemical, optical and photovoltaic properties of all the MPcs as sensitizers were examined. Electrochemical studies reveal that while the ZnPc (4) and NiPc (6) give only Pc ring-based redox reactions, the CoPc (5) shows the redox reactions based on both the central metal and the ring due to the metal 3d orbitals locate between the Pc HOMO and LUMO. The DSSC based on 5 gave the lowest power conversion efficiency (0.51%), perhaps due to the presence of a redox active central metal ion in the core of the complex, which results in a decrease electron transfer in the device. However, the DSSCs based on the redox inactive central metal ions, which cannot reduce electron transfer, showed reasonable power conversion efficiencies of 1.27% and 1.11% for 4 and 6, respectively. The slight difference between the efficiencies can be attributed to narrower band gap and higher molar extinction coefficient of 4 than 6, which ensure a broader light absorption in the visible region and higher photocurrent. Keywords: Chalcone, Phthalocyanine, Metal ions, Electrochemistry, Dye-sensitized solar cells.