Role of sulfur in the absorption spectrum bathochromic shift of

Role of sulfur in the absorption spectrum bathochromic shift
of organic dyes for DSSC
Ottavia Bettucci,a,b Massimo Calamante,b,c Alessandro Mordini,b,c Adalgisa Sinicropi,a Lorenzo Zani,b Gianna Reginato.b
aDipartimento di
bIstituto
Biotecnologie Chimica e Farmacia, Università degli Studi di Siena, via A. Moro 2, 53100 Siena, Italy.
di Chimica dei composti organometallici (CNR-ICCOM), via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy.
cDipartimento di
Chimica “U. Schiff” Università degli Studi di Firenze, via della Lastruccia 13, 50019 Sesto Fiorentino, Italy.
e-mail: [email protected]
Dye Sensitized solar cells (DSSC) are a third generation photovoltaic technology that converts
One of the most important parameters
visible light into electrical energy. The main components of a DSSC are:
of dyes for DSSC is the capability to
•
•
absorb light in a specific visible part
of the solar spectrum. As we can see in
•
the picture, the sun emits mostly in the
•
•
range of 500-800nm so it is essential
In this work the dyes
CONDUCTIVE GLASS (TCO)
THIN FILM OF NANOCRYSTALLINE TiO2
synthesised are organic
compounds with a D- π -A
DYE absorbed on the semiconductor
ELECTROLYTE working as the redox mediator
can be divided in three parts:
CONDUCTIVE GLASS covered with Pt
a Donor, a π -bridge and
prepare and employ dyes that absorb mostly in this range. Theoretical studies[1][2]
could give a red-shift of its λmax of absorption and in general broaden its
attention mostly on the shift of λmax.
Ambrosio,F.; Martsinovich, N.; Troisi, A. J. Phis. Chem. Lett. 2012, 3, 1531
Purpose of work
MS14
MS20
MS13
1,0
0,8
0,2
600
Wavelength nm.
700
800
S
O
CN
HexO
Lawesson's
Reagent
Lumo
EtOH
488
CH 2Cl2
517
the absorption maxima, calculations showed an appreciable
red-shift of around 20 nm, in two different solvents.
HO
OH
CN
HexO
N
H
S
S
CN
OH
O
H
HexO
OB91
λ max= 459
OB47
λ max= 556
HexO
OB18
OB19
Absorbance
0,4
450
500
550
600
Wavelength (nm)
650
700
400
0,4
0,0
400
500
Wavelength nm.
600
In both cases the UV spectra were measured
0,4
in CH2Cl2 showing a red-shift of the λmax of
0,0
0,0
0,6
0,2
0,6
0,2
0,2
400
0,8
0,8
0,6
OB91
OB89
1,0
OB47
DF15
1,0
0,8
OB89
λ max= 429
75%
S
N
ACN, relfux, 3,5h
96%
1) THF, -78°C. 1,5h
2) -78 °C-rt, 16h
HexO
N
OB19
λ max= 550
O
DF15
λ max= 529
toluene, 90°c
30'
1,0
λmax was around 35 nm
536
so we can suppose a good application in devices. Concerning
1) nBuLi
2) DMF
N
Anchoring groups containing sulfur: THIOAMIDES
CH2Cl2 and the red-shift of the
506
basically the same for OB47 and DF15 (already tried in cell),
HexO
MS20 and MS14, accompanied by large spectral broadening
OB18
λ max= 516
EtOH
CH 2Cl2
λmax
(nm)
DF15
Anchoring groups containing sulfur: THIOCYANOACRYLIC ACIDS and THIOACIDS
The preliminary study consisted in the synthesis of three
The UV spectra were measured in
λmax
(nm)
MS14
λ max= 597
between MS20 and MS13 and around 75 nm between
0,0
Homo
Homo
Applications in
DSSC
CH2Cl2 showed a very impressive red-shift of around 25 nm
500
OB47
The charge distribution in the LUMO and HOMO orbitals is
and 2 sulfur atoms. The spectroscopic analysis, carried out in
0,4
DF15
conduction band and the regeneration of the dye.
Lumo
esters (MS20, MS13, MS14) containing respectively 0, 1
0,6
400
redox potential. This is fundamental for the injection of electrons in the
Computational
studies
Absorbance
Absorbance
MS13
λ max= 549
O
HexO
Absorbance
MS20
λ max= 522
OH
than the energy of TiO2 conduction band and if the HOMO is lower than I3-/I-
Principles of a
DSSC
Preliminary
studies
DF15
S
COMPUTATIONAL STUDIES (DFT) were carried out in order to evaluate the
OB47
STARTING
PRODUCT
O
O
S
levels. This last information is useful to verify if the LUMO energy level is higher
introducing sulfur atoms starting from a known structure and focused our
[2]
S
C6H13 NC
λmax of dyes, charge distribution of frontier molecular orbitals and the energy
spectrum. In the present work we wanted to demonstrate these benefits
Yang, L.N.; Sun, Z.Z.; Chen, S.L.; Li, Z.S. Dyes Pigments 2013, 99, 29
C6H13 Si
N
an Acceptor group
have shown that the introduction of a sulfur atom in the acceptor group of a dye
[1]
HexO
structure. These molecules
450
500
550
600
Wavelength (nm)
650
700
around 30 nm and an appreciable spectral
broadening.

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