LAAN-A-LM-E046
Liquid Chromatography Mass Spectrometry
No.C75
Analysis of Impurities of Ru Dye (N719) for Dye-Sensitized Solar Cells
Solar cells are classified into several types, including a
crystalline silicon type, a thin-film silicon type, a
compound system type (CIGS, etc.), and the organic
system type (organic thin-film type and dye-sensitized
type), etc. Of these, about 90 percent of the solar cells
being manufactured now are crystalline silicon solar
cells. However, due to their manufacturing cost and
the instability of a high-purity silicon supply, research
and development of the next generation of dyesensitized solar cell is being promoted.
The dye-sensitized solar cell is based on a system
that generates electricity using dyes that are excited
by light. This design has the advantages of high
flexibility in determining color and shape, as well as
low manufacturing cost. However, a variety of
problems with this approach must first be addressed,
including a solar conversion efficiency that is only
about 1/3 that of the crystalline silicon type, and
reliability (endurance), etc. In particular, even a minute
amount of impurity in the dye will have a very adverse
affect on the solar conversion efficiency. Here we
introduce an example of the separation and qualitative
analysis of impurities in the widely used dye, Ru
N719, using the LCMS-2020.
*The Ru N719 dye was kindly provided by Dr. Liyuan Han of the NIMSAdvanced Photovoltaics Center in Ibaraki, Japan.
n Flow Injection Analysis of N719 Using LCMS-2020
N719 is a dye with improved solar conversion
efficiency which is derived from N3 by the bonding of
tetrabutylammonium (TBA) at 2 of the carboxyl sites of
the N3 dye. Fig. 1 shows the structure of N719. After
dissolving the N719 sample in ethanol, ESI
measurement was conducted. Fig. 2 shows the
positive and negative mass spectra obtained. In the
ESI positive mode, the tetrabutylammonium molecular
ion was detected, while deprotonated molecules of
compounds bonded with 0 to 3 tetrabutylammonium
groups, as well as doubly-charged ions, etc. were
detected using the ESI negative mode.
○0 tetrabutylammonium detected
N+
COOH
N719
COOH
HOOC
OOC
COOH
N
N
SCN
Ru
SCN
N
Ru
N
NCS
COO-
C58H86N8O8RuS2
Exact Mass : 1188.51
Mol. Wt. : 1188.55
N+
COOH
N
N
-
NCS
N3
N
N
C26H16N6O8RuS2
Exact Mass : 705.95
Mol. Wt. : 705.64
COOH
○1 tetrabutylammonium detected
C42H51N7O8RuS2
Exact Mass : 947.23
Mol. Wt. : 947.10
N3 [TBA]
○3 tetrabutylammonium detected
C74H121N9O8RuS2
Exact Mass : 1429.78
Mol. Wt. : 1430.01
N3 [TBA]3
Fig. 1 Structure of N719
5.0
Inten. (× 1,000,000)
242.3
ESI (+)
Tetrabutylammonium (TBA)
4.0
N+
3.0
2.0
C16H36N+
Exact Mass : 242.28
Mol. Wt. : 242.46
1.0
0.0
1.5
1.0
0.5
0.0
250
Inten. (× 1,000,000)
500
750
364.3
Doubly-charged
351.8
ion of N3
Doubly-charged
ion of N3 [TBA]
263.0
Doubly-charged
472.4
ion of N719
N3
593.6
705.0
635.5
197.0
250
500
750
1000
1250
1500
m/z
ESI (--)
824.7
N3 [TBA]
946.4
1000
Fig. 2 FIA Mass Spectra of N719
1067.5
N719
1187.7
1250
N3 [TBA]3
1428.9
1500
m/z
No.C75
n Analysis of Impurities of N719 Using LCMS-2020
By conducting the analysis under acidic conditions,
separation of N3 dye impurities having different
structures at the X and Y sites was achieved. Fig. 3
shows the LC and MS chromatograms, and Fig. 4
shows the mass spectra at peaks A, B, F, and N3.
6.0
(× 10)
N3
COOH
5.0
HOOC
4.0
3.0
COOH
N
Ru
X
1.0
0.0
0.0
(× 10,000,000)
2.5
F
N
N
2.0
2.5
Separation of N3 and compound F, which is difficult
using the typical ODS column, was easily achieved
using these conditions, demonstrating the ease with
which quality control can be conducted.
N
Y
COOH A
5.0
B
7.5
C D E
10.0
12.5
2.0
15.0
min
1: TIC
F
1.5
A
1.0
B
Tetrabutylammonium
C
G
0.5
0.0
0.0
2.5
5.0
7.5
10.0
PDA Ch1 (532 nm)
12.5
15.0
min
1: 689.00 (28.85)
1: 674.95 (100.00)
1: 706.95 (24.20)
1: 242.10 (1.11)
1: 219.00 (5.81)
Fig. 3 Chromatograms of N719 in Ethanol Solution
A
Inten. (× 10,000)
3.0
186.1
2.0
60.0
1.0
131.1
250
B
Inten. (× 100,000)
112.3
0.5
83.0
0.0
689.0
237.2 328.7
0.0
1.0
[M+H]+
531.5
500
750
m/z
X: -NCS
Y: -CN
648.0
[M+H]+
707.0
5.0
750
0.0
m/z
X: -SCN
Y: -NCS
421.6
250
N3
Inten. (× 100,000)
500
5.0
2.5
[M+H]+
675.0
500
7.5
2.5
648.0
186.0
250
X: -NCS
Y: -CH3CN
F
Inten. (× 10,000)
0.0
750
648.0
[M+H]+
707.0
m/z
X: -NCS
Y: -NCS
186.4
250
500
750
m/z
Fig. 4 ESI(+) Mass Spectra of Impurities A, B, F and N3
Table 1 Analytical Conditions for LC/MS
Column
Mobile Phase A
Mobile Phase B
Gradient Program
Flow Rate
Injection Volume
Column Temperature
: Phenomenex Fusion RP (150 mmL. × 2.0 mm I.D., 4 μm)
: 1 % formic acid - water
: acetonitrile
: 5 %B (0 min) - 75 %B (15-20 min)- 5 %B (20.01 - 30 min)
: 0.2 mL/min
: 2 μL
: 25 °C
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Cable Add.:SHIMADZU TOKYO
Probe Voltage
: +4.5 kV (ESI-Positive mode),
-3.5 kV (ESI-Negative mode)
: 1.5 L/min
Nebulizing Gas Flow
: 10 L/min
Drying Gas Flow
: 250 °C
DL Temperature
Block Heater Temperature : 450 °C
: default values
DL, Q-Array Voltages