In this chapter, recent progress in the applications of tetrapyrrolic free-base
as well as its metal complexes in dye-sensitized solar cells (DSSC) is summarized and
analyzed. Though ruthenium(II) complexes are dominant in DSSC, but they have
certain drawbacks to necessitate the design of alternative sensitizers. Based on
absorption, thermal and redox properties, tetrapyrrolic compounds are found to be
alternative sensitizers to ruthenium(II) complexes. Tetrapyrroles are broadly divided
into three categories and they are porphyrins, phthalocyanines and corroles. Both
porphyrins and phthalocyanines are good sensitizers to wideband-gap semiconductors.
Two classes of porphyrins are defined by connecting position of anchoring groups
either at meso- or at pyrrole-β. The effect of efficiency of DSSC device with
substituents on porphyrin ring is reviewed. Phthalocyanines are another class of
tetrapyrrolic compounds and they are less explored for DSSC applications due to
aggregation and solubility of macrocycle in common organic solvents. New
unsymmetrical phthalocyanines are designed based on ‘push-pull’ concept is analyzed.
The possibility of application of corroles as sensitizers for DSSC is also reviewed.
Keywords: Corroles, porphyrins, phthalocyanines, sensitizers, tetrapyrroles.
