chemistry are the main values of those materials and make the porphyrin family a
great interest.
Another very good example of porphyrin species are phthalocyanines that can be
potentially used in photovoltaics. Phthalocyanines were discovered at the beginning
of the last century (1907) [4] and in that time and now they have been studied as
functional materials. When compared to porphyrin their macrocycles are build of
four indole units connected with azomethine groups instead of methine bridges.
Phthalocyanines are porphyrin-like dyes, and they belong to heterocyclic groups
which are characterized by: high chemical and physical stability, effective intermolecular electron transfer, easiness of molecular structure modification.
Phthalocyanine derivatives can change the color from red to blue depending on
metal ion inside the macrocycle. Phthalocyanines like porphyrins are also of a great
interest as photosensitizers to many scientific and technological applications.
Non-substituted phthalocyanines and some of their metalized derivatives and
complexes show rather poor solubility. Moreover, the substitution influences a shift
of the absorption bands toward the lower wavelengths. However, thanks to great
possibilities of modifying phthalocyanines molecular structure as well their particular photophysical and photochemical properties, they give a wide range of
possibilities to be used in many fields of molecular optoelectronics. Besides, the
substitution, many Pc are characterized by good solubility. The dyes are characterized not only by strong absorption in the visible light, but some of them show
fluorescence. Also they are characterized by very high resistance to light, weak
influence of additional rings and metal ions on some spectral properties.
Both porphyrins and phthalocyanines are characterized by strong absorption
bands; porphyrin strong band is observed in the Soret region (420–450 nm) and
much less intense Q bands in the long-wavelength region [5]. Contrary, in
phthalocyanines the Q bands in the long-wavelength region (650–680 nm) are
much intensive whereas the less intense bands in the range of the Soret bands are
present [5].
The studies of spectral and photoelectric properties of a series of porphyrins and
phthalocyanines in the simple or more complex systems [6–27] as potential photosensitizers are required to find a correlation between molecular structure of
chromophores and their ability in photocurrent creation. Any change in the
molecular structure of dyes causes dissimilarity of spectroscopic properties and in
consequence in modification of photoactive properties. Typical examples for basic
porphyrins are: metal-free porphyrin (free-base tetraphenylporphyrin—H 2 TPP),
metallic porphyrins (MTPP—e.g., MgTNP, ZnTNP, PbTNP, CuTNP), metallic
tetranaphenylporphyrin (MTNP). For example, magnesium and zinc porphyrins
(MgTPP and ZnTPP, respectively) have large molar absorption coefficients and
good effectiveness in light energy to electric energy conversion. In contrast to those
dyes, free-base and lead porphyrins (H 2 TPP and PbTPP, respectively) are rather not
efficient in photoconversion. Likewise, the representatives of the phthalocyanine
3 Quantum Dot and Fullerene with Organic Chromophores as …
101
great interest.
Another very good example of porphyrin species are phthalocyanines that can be
potentially used in photovoltaics. Phthalocyanines were discovered at the beginning
of the last century (1907) [4] and in that time and now they have been studied as
functional materials. When compared to porphyrin their macrocycles are build of
four indole units connected with azomethine groups instead of methine bridges.
Phthalocyanines are porphyrin-like dyes, and they belong to heterocyclic groups
which are characterized by: high chemical and physical stability, effective intermolecular electron transfer, easiness of molecular structure modification.
Phthalocyanine derivatives can change the color from red to blue depending on
metal ion inside the macrocycle. Phthalocyanines like porphyrins are also of a great
interest as photosensitizers to many scientific and technological applications.
Non-substituted phthalocyanines and some of their metalized derivatives and
complexes show rather poor solubility. Moreover, the substitution influences a shift
of the absorption bands toward the lower wavelengths. However, thanks to great
possibilities of modifying phthalocyanines molecular structure as well their particular photophysical and photochemical properties, they give a wide range of
possibilities to be used in many fields of molecular optoelectronics. Besides, the
substitution, many Pc are characterized by good solubility. The dyes are characterized not only by strong absorption in the visible light, but some of them show
fluorescence. Also they are characterized by very high resistance to light, weak
influence of additional rings and metal ions on some spectral properties.
Both porphyrins and phthalocyanines are characterized by strong absorption
bands; porphyrin strong band is observed in the Soret region (420–450 nm) and
much less intense Q bands in the long-wavelength region [5]. Contrary, in
phthalocyanines the Q bands in the long-wavelength region (650–680 nm) are
much intensive whereas the less intense bands in the range of the Soret bands are
present [5].
The studies of spectral and photoelectric properties of a series of porphyrins and
phthalocyanines in the simple or more complex systems [6–27] as potential photosensitizers are required to find a correlation between molecular structure of
chromophores and their ability in photocurrent creation. Any change in the
molecular structure of dyes causes dissimilarity of spectroscopic properties and in
consequence in modification of photoactive properties. Typical examples for basic
porphyrins are: metal-free porphyrin (free-base tetraphenylporphyrin—H 2 TPP),
metallic porphyrins (MTPP—e.g., MgTNP, ZnTNP, PbTNP, CuTNP), metallic
tetranaphenylporphyrin (MTNP). For example, magnesium and zinc porphyrins
(MgTPP and ZnTPP, respectively) have large molar absorption coefficients and
good effectiveness in light energy to electric energy conversion. In contrast to those
dyes, free-base and lead porphyrins (H 2 TPP and PbTPP, respectively) are rather not
efficient in photoconversion. Likewise, the representatives of the phthalocyanine
3 Quantum Dot and Fullerene with Organic Chromophores as …
101