Photochemical investigation of porphyrins for use in Dye Sensitized Solar Cells
Date
2012-07-13
Authors
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Journal ISSN
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ORCID
Type
Degree Level
Masters
Abstract
As Dye Sensitized Solar Cells (DSSCs) have become a more prominent focus of the research
being published on alternative energy sources it is important to consider basic principles that
show promise for improving the energy conversion efficiency of these cells. By choosing and
building a dye system carefully it is possible to promote a process called triplet-triplet
annihilation (TTA) which involves the upconversion of two relatively low energy triplet excited
molecules to produce one highly excited singlet molecule and a ground state molecule (2 T1
Sn + S0 [n>1]). This process will give DSSCs the ability to take advantage of the photon-rich near
infrared portion of the solar spectrum making them inherently more efficient than systems
which cannot undergo TTA.
Two dye systems which show promise as TTA capable light harvesters are zinc
tetraphenylporphyrin (ZnTPP) and tin(IV)-dichloro,tetraphenylporphyrin (SnCl2TPP). The
photophysical properties of ZnTPP are studied in its standard form as well as in its ligated form.
Ligation of the central atom with nitrogen containing bidentate ligands (i.e. pyrazine, 4,4-
bipyridine etc…) can have a profound effect on both the properties of the monomer as well as
the aggregate behavior of solvated dyes and their interaction with each other. The properties of
SnCl2TPP are also examined and in particular methods for the formation of stacked molecular
columns as manipulation of interactions between the individual dyes can significantly impact
their ability to undergo TTA.
Spectral data indicate that ligation of the ZnTPP leads to the formation of a short lived charge
transfer state which greatly decreases the lifetime of the S2 state while having little effect on
the S1 decay kinetics. It also shows that there is little or no formation of six-coordinate ZnTPP
(i.e. doubly ligated) which makes the formation of stacked supramolecular structures very
difficult. Data concerning the electrochemical synthesis and chemical synthesis of a SnCl2TPP
based stack were inconclusive but show some promise that may give direction to future work.
Description
Keywords
Dye Sensitized Solar Cell, Porphyrin, Triplet triplet annihilation, Upconversion, Solar efficiency, DSSC, ZnTPP, supramolecular porphyrin synthesis
Citation
Degree
Master of Science (M.Sc.)
Department
Chemistry
Program
Chemistry