Surface modification of DSSSCs by atmospheric plasma jet
Shogo KANETA1, Marius BLAJAN2, Kenta OGI1, Akinori Konno3 and Kazuo SHIMIZU2
1Graduate School of Engineering, Shizuoka University
2Organization for Innovation and Social Collaboration, Shizuoka University
3Graduate School of Science and Technology, Shizuoka University

Johoku, Hamamatsu, 432-8561, Japan
E-mail：shimizu@cjr.shizuoka.ac.jp(3) Effect of humidity
Dry treatment (dry process gas with relative
humidity 0%), and wet treatment (humid process gas
with relative humidity 65%) were carried out(Figure 5).Dry treatment improved the conversion
efficiency. Improvement rate increased with about
20% after 15 min. Wet treatment worsened theconversion efficiency. After 15 min of wettreatment, improvement rate decreased with about
45%.

INTRODUCTION
The dye-sensitized solid-state solar cells (DSSSCs)
could have the potential to be alternatives to theexistent DSSCs. However, solar conversion efficiency
of DSSSCs is lower than that of conventional DSSCs
efficiency [1]. Surface treatment of dye-sensitizedsolid-state solar cells by atmospheric pressureplasma jet was studied to improve its efficiency.

METHODS(1)Experimental setupFigure. 1 shows an experimental setup for surface
modification. The plasma jet electrode was poweredby an AC high voltage power supply. The process gas
was fed through the glass tube from gas cylinders.
DSSSCs sample and the plasma jet electrode wereplaced into a chamber. An Ar/O2 mixture (5.00 + 0.25
L/min.) was used as the process gas. Additionally, theprocess gas can be humidified (relative humidity 65%).
The frequency of AC high voltage was set at 16.1
kHz. Discharge voltage was 5.0 kV (Figure. 2 (a)).
Distance between cathode and TiO2 sample was 13mm. Figure. 2 (b) shows an image of light emission ofAr + O2 plasma discharge.

Fig. 3 I-V characteristics before and after various
treatment times (5, 10 and 15 min.).

Table 1. Characteristics of various DSSCs
Treatment
Jsctime[mA/cm2][min.]

Voc[V]

FFη
[%]

Untreated

4.25

0.54

0.69

1.60

54.32

0.55

0.70

1.65

10

4.82

0.49

0.71

1.67

15

5.35

0.51

0.72

1.96

Fig. 5 Effect of humidity in the carrier gas.

(4) Contact angle measurement
Figure 6 shows the result of contact anglemeasurement. The contact angles was decreased to11.7° after dry treatment The contact angle wasdecreased to 10.2° wet treatment. Hydrophilicgroup modification could be occurred bothtreatments.

(2) XPS analysis
The surface stoichiometry was determined bycalculating the relative peaks area as ratio of thetotal Ti 2p and O 1s in XPS spectra (Figure 4). Table.
2 shows chemical composition of TiO2 surface
before and after treatment. Ti3+ peaks and Ti2O3peaks were increased after plasma treatment.
Fig. 1 An experimental setup for TiO2 sample surface
modification.

Figure 6. The appearance of water droplet on TiO2 surface.
(a) Untreated (b) Dry treated (c) Wet treated(a)Fig. 2 (a) current-voltage wave form.

(5) Dye adsorption quantity

Fig.4 (a) XPS spectra of Ti 2p on the TiO2 surface(treated 15 min.).

Figure. 7 shows dye adsorption quantity of TiO2
surface after plasma treatment. After Dry
treatment, dye adsorption quantity increased withabout 5%. On the other hand, after Wet treatment,
dye adsorption amount decreased with about 20%.
Hydrophilic group modification could have been
occurred during both types of treatment. However,humidity in process gas inhibited the dye
adsorption and decreased the conversion efficiency.

(b)
Fig. 2 (b) image of Ar + O2 plasma discharge.
Fig.7 Dye adsorption quantity of TiO2 surface versus
treatment time

RESULTS(1)Photovoltaic measurements
The size of the TiO2 sample was 0.5 cm2. After theplasma exposure treatment, The TiO2 sample wassoaked to dye again for about 18 hours. N719
Ruthenium-based dye was used. I-V characteristics
were measured under simulated solar light (AM 1.5,100mW/cm2) using a solar cell evaluation system(JASCO, CEP-25BX). Treatment time of sample
surface was 5, 10 and 15 min. The target sample wasattached in the chamber and relative humidity inchamber was 0%. 3 samples were treated each time.
Figure. 3 and Table. 1 show the result of photovoltaicmeasurements. Efficiency was improved withincreasing treatment time because the short circuit
photocurrent density was increased by plasma
treatment.

Fig.4 (b) XPS spectra of O 1s on the TiO2 surface(treated 15 min.).

Table 2. Chemical composition of TiO2 surface.
Ti 2p

Ti4+ 2p1/2

Ti4+ 2p3/2

Ti3+ 2p1/2

Ti3+ 2p3/2

No treated

29.52

67.21

2.39

0.88

15 min

29.61

66.48

2.93

0.97

O 1sTiO2

Ti2O3

No treated

72.99

27.01

15 min

67.81

32.19

CONCLUSIONSIn this study, the following conclusions wereobtained.
1. TheDSSSCssurface
modification
using
atmospheric pressure plasma jet improved theconversion efficiency of DSSSCs.
2. The electric conductivity of the DSSSC sample
surface was increased after 15min of plasma
treatment.
3. Humidity in the carrier gas decreased theconversion efficiency of DSSSCs because
humidity in process gas inhibited the dye
adsorption.

REFERENCE[1] A. Konno and EVA Premalal, J. Photopolym. Sci.
Technol, 23 279 (2010).