Dye-sensitized solar cells (DSSC) are energy devices that convert
light energy into electricity, based on the sensitization of
wide-band gap metal oxide semiconductors such as TiO2 [1,2].
Successfully demonstrated by O’Regan and Gratzel in 1991 [1],
the DSSC devices have attracted a lot of interest towards development
and improvement of new families of dyes [3]. DSSCs sensitized
with dyes having heavy transition-metal complexes such as
ruthenium based complexes are the most efficient and have been
recorded to operate with power conversions efficiency reaching
as high as 11–12% using nanoporous TiO2 electrodes [4–6]. However,
ruthenium polypyridyl complexes contain a heavy metal,
which is undesirable from environmental concerns [7]. Additionally,
the high cost of ruthenium complexes and the long-term
unavailability of these noble metals [4–9] switch the need to
search for alternative photosensitizers to be used for TiO2-based
photovoltaic devices. Alternatively, natural dyes can be used for
the same purpose with an acceptable efficiency [7,10–16].
Recently, research has focused on the easily available dyes
extracted from natural sources as a photosensitizer because of
their large absorption coefficients, high light-harvesting efficiency,
low cost, easy preparation and environment friendliness