LAAN-A-LM-E046

No.C75Liquid Chromatography Mass Spectrometry

Analysis of Impurities of Ru Dye (N719) for Dye-Sensitized Solar CellsSolar 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 dye-sensitized 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 NIMS- Advanced Photovoltaics Center in Ibaraki, Japan.

n Flow Injection Analysis of N719 Using LCMS-2020N719 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.

C42H51N7O8RuS2Exact Mass : 947.23

Mol. Wt. : 947.10

C26H16N6O8RuS2Exact Mass : 705.95

Mol. Wt. : 705.64

C74H121N9O8RuS2Exact Mass : 1429.78

Mol. Wt. : 1430.01

○0 tetrabutylammonium detected N3

○1 tetrabutylammonium detected N3 [TBA]

○3 tetrabutylammonium detected N3 [TBA]3

N

Ru

NCS

NN

NSCN

-OOC

COOH

COOH

COO-

N+

N+C58H86N8O8RuS2

Exact Mass : 1188.51Mol. Wt. : 1188.55

N719

N

Ru

NN

NSCN

HOOCCOOH

COOHNCS

COOH

Fig. 1 Structure of N719

Fig. 2 FIA Mass Spectra of N719

242.3

364.3351.8

263.0 472.4

593.6

197.0

N+ C16H36N+

Exact Mass : 242.28Mol. Wt. : 242.46

Tetrabutylammonium (TBA)

Doubly-chargedion of N3

Inten. (× 1,000,000)5.0

4.0

3.0

2.0

1.0

0.0m/z250 500 750 1000 1250 1500

m/z250 500 750 1000 1250 1500

Inten. (× 1,000,000)

1.5

1.0

0.5

0.0

ESI (+)

ESI (--)

705.0N3 946.4

N3 [TBA]

824.7635.5 1067.5 1187.7N719

1428.9N3 [TBA]3

Doubly-chargedion of N719

Doubly-chargedion of N3 [TBA]

SHIMADZU CORPORATION. International Marketing Division3. Kanda-Nishikicho 1-chome, Chiyoda-ku, Tokyo 101-8448, Japan Phone: 81(3)3219-5641 Fax. 81(3)3219-5710Cable Add.:SHIMADZU TOKYO

No.C75

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.

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 Analysis of Impurities of N719 Using LCMS-2020

(× 10)

(× 10,000,000)

A BG

F

C

N3

BD EA C

F

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)

1: TIC

Tetrabutylammonium

2.5

2.0

1.5

1.0

0.5

0.0

6.0

5.0

4.0

3.0

2.0

1.0

0.00.0 2.5 5.0 7.5 10.0 12.5 15.0 min

0.0 2.5 5.0 7.5 10.0 12.5 15.0 min

N

Ru

Y

NN

NX

HOOC

COOH

COOH

COOHPDA Ch1 (532 nm)

Fig. 3 Chromatograms of N719 in Ethanol Solution

A

3.0

2.0

1.0

0.0

7.5

5.0

2.5

0.0250 500 750 m/z

Inten. (× 10,000)FInten. (× 10,000)

186.1

689.060.0

131.1 648.0237.2 328.7 531.5

[M+H]+ [M+H]+X: -NCSY: -CH3CN

250 500 750 m/z

X: -SCNY: -NCS

B

1.0

0.5

0.0250 500 750 m/z

5.0

2.5

0.0250 500 750 m/z

Inten. (× 100,000)N3Inten. (× 100,000)

[M+H]+

[M+H]+X: -NCSY: -CN

X: -NCSY: -NCS

648.0

707.0421.6

112.3

186.0675.083.0

648.0

707.0

186.4

Fig. 4 ESI(+) Mass Spectra of Impurities A, B, F and N3

Column : Phenomenex Fusion RP (150 mmL. × 2.0 mm I.D., 4 μm) Probe Voltage : +4.5 kV (ESI-Positive mode),Mobile Phase A : 1 % formic acid - water -3.5 kV (ESI-Negative mode)Mobile Phase B : acetonitrile Nebulizing Gas Flow : 1.5 L/minGradient Program : 5 %B (0 min) - 75 %B (15-20 min)- 5 %B (20.01 - 30 min) Drying Gas Flow : 10 L/minFlow Rate : 0.2 mL/min DL Temperature : 250 °CInjection Volume : 2 μL Block Heater Temperature : 450 °CColumn Temperature : 25 °C DL, Q-Array Voltages : default values

Table 1 Analytical Conditions for LC/MS