Novel Co and Zn-Phthalocyanine dyes with octa-carboxylic acid substituents for DSSCs

In this work, novel octakis (thioglycolic acid) and (mercaptopropionic acid) substituted phthalocyanines (Pcs), having cobalt(II) and zinc(II) ions in the macrocyclic core, have been prepared to be used as sensitizers in dye sensitized solar cells (DSSCs). The electrochemical parameters of synthesized Pcs have been investigated by cyclic voltammetry and square wave voltammetry results. The HOMO and LUMO orbital levels of synthesized phthalocyanine (Pc) dyes have been determined and the suitability of their HOMO and LUMO levels with DSSCs has been discussed in detail. The glycolic acid substituted Pcs have higher solar cell efficiency values than propionic acid derivatives because of their electron transportation pathway differences. Among the synthesized metal complexes, glycolic acid substituted ZnPc has been found to have the highest DSSC efficiency value of 2.45%. This complex dye has also been found to have the lowest resistance (8.95 O), longest electron life time (17.19 ms) and shortest electron transport time (0.33 ms) according to electrochemical impedance spectroscopy (EIS) studies.