aggregation, molecular orientation, fluorescence quenching, reorganization energy,
HOMO and LUMO levels as well as processes of energy/electron transfer and
electron redistribution. These materials are gaining a lot of interest not only among
chemists, but also physicists and materials engineers.
As it appears from the above, it will be a chapter giving a brief outline of the
mechanisms and processes occurring in photoactive organic materials important for
their prospective applications and can serve as one of the basic sources of information about new materials. The research methods used to study organic materials
were conventional and unconventional spectroscopic methods, supported by computer simulations.
3.2 Brief History of Photocells Based
on Organic Materials
So far, the photoactive materials, which are used for solar cell manufacture, are
based on germanium, silicon, gallium arsenide, amorphous silicon and their alloys,
and others. However, efficiency of commercial solar cells based on such materials
does not exceed 12%, and their great disadvantage is high cost when compared with
conventional sources of electric power.
In the first dye-sensitized photovoltaics (DSPV), the photoactive molecules were
sensitive to the UV and blue light [1–10]. However, over the past few decades
intense research to improve DSPV have brought a great evolution in photocell
designs which stemmed from the use of a series of p-electron dyes and their
complexes working in DSPV as photosensitizers [4]. Among them there are cells
based on porphyrins, phthalocyanines and other macrocyclic dyes absorbing
intensively in the visible range [7–10]. The first successful solid hybrid
dye-sensitized solar cells were reported to improve electron transport. Numerous
research groups have experimented with a wide variety of a family of organic
porphyrin dyes; however, DSPV with such materials reached rather low efficiency
[5, 6]. Many new dye-sensitized solar cells based on organic functional dyes
comprised of porphyrins covalently linked with other moieties such as terthiophenes building blocks, rhodamines or ruthenium complexes have been also
extensively reported as photosensitizers for developing photoelectrochemical solar
cells [7–10]. Also porphyrin-sensitized TiO 2 or systems with porphyrin-gold
nanoparticles [7, 11] were demonstrated as materials for a new cell that directly
converts light energy into electricity. Many groups of scientists have presented the
results of the chromophore-based DSPV devices with different working media:
from traditional organic liquid electrolytes, ionic liquid electrolytes, polymer gel
electrolytes, quasi-solid state to self-assembled monolayer, Schottky barrier cells,
and other systems [7–11]. In many cases, these DSPV systems offer high photovoltaic effect, chemical and thermal stability as well as opportunity for developing
long-term operational solar cells. The basic spectroscopic properties of photoactive
dyes and interrelation between the molecular structure of dyes and their ability to
3 Quantum Dot and Fullerene with Organic Chromophores as …
99
HOMO and LUMO levels as well as processes of energy/electron transfer and
electron redistribution. These materials are gaining a lot of interest not only among
chemists, but also physicists and materials engineers.
As it appears from the above, it will be a chapter giving a brief outline of the
mechanisms and processes occurring in photoactive organic materials important for
their prospective applications and can serve as one of the basic sources of information about new materials. The research methods used to study organic materials
were conventional and unconventional spectroscopic methods, supported by computer simulations.
3.2 Brief History of Photocells Based
on Organic Materials
So far, the photoactive materials, which are used for solar cell manufacture, are
based on germanium, silicon, gallium arsenide, amorphous silicon and their alloys,
and others. However, efficiency of commercial solar cells based on such materials
does not exceed 12%, and their great disadvantage is high cost when compared with
conventional sources of electric power.
In the first dye-sensitized photovoltaics (DSPV), the photoactive molecules were
sensitive to the UV and blue light [1–10]. However, over the past few decades
intense research to improve DSPV have brought a great evolution in photocell
designs which stemmed from the use of a series of p-electron dyes and their
complexes working in DSPV as photosensitizers [4]. Among them there are cells
based on porphyrins, phthalocyanines and other macrocyclic dyes absorbing
intensively in the visible range [7–10]. The first successful solid hybrid
dye-sensitized solar cells were reported to improve electron transport. Numerous
research groups have experimented with a wide variety of a family of organic
porphyrin dyes; however, DSPV with such materials reached rather low efficiency
[5, 6]. Many new dye-sensitized solar cells based on organic functional dyes
comprised of porphyrins covalently linked with other moieties such as terthiophenes building blocks, rhodamines or ruthenium complexes have been also
extensively reported as photosensitizers for developing photoelectrochemical solar
cells [7–10]. Also porphyrin-sensitized TiO 2 or systems with porphyrin-gold
nanoparticles [7, 11] were demonstrated as materials for a new cell that directly
converts light energy into electricity. Many groups of scientists have presented the
results of the chromophore-based DSPV devices with different working media:
from traditional organic liquid electrolytes, ionic liquid electrolytes, polymer gel
electrolytes, quasi-solid state to self-assembled monolayer, Schottky barrier cells,
and other systems [7–11]. In many cases, these DSPV systems offer high photovoltaic effect, chemical and thermal stability as well as opportunity for developing
long-term operational solar cells. The basic spectroscopic properties of photoactive
dyes and interrelation between the molecular structure of dyes and their ability to
3 Quantum Dot and Fullerene with Organic Chromophores as …
99