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A Study on the Effects of Siloxane Derivatives as Co-adsorbents on the Performance of Dye-sensitized Solar Cells
Available online at www.sciencedirect.com
ScienceDirect Energy Procedia 61 (2014) 842 – 845
The 6th International Conference on Applied Energy – ICAE2014
A Study on the Effects of Siloxane Derivatives as Coadsorbents on the Performance of Dye-Sensitized Solar Cells Cheng-Lan Lina,b,* and Chun-Ming Chua a
Department of Chemical and Materials Engineering, Tamkang University, 151 Yingzhuan Road, New Taipei City 25137, Taiwan b The Energy and Opto-Electronic Materials Research Center, Tamkang University, New Taipei City 25137, Taiwan
Abstract In this study, tetraethoxysilane (TEOS) or phenyltriethoxysilane (PTEOS) is used as the co-adsorbent with N719 dye to prepare the photoanode for a dye-sensitized solar cell (DSSC), and its effects on the photovoltaic performances of the DSSC are investigated. It is found that both the short-circuit current and the open-circuit voltage of the DSSC are increased with the co-adsorption of TEOS or PTEOS on the mesoporous TiO2 photoanode. Electrochemical impedance spectra indicate that the electron lifetime is improved. The energy conversion efficiency of the DSSC is promoted from 4.55 % to 4.97% or 5.10 %, respectively, when TEOS or PTEOS is co-adsorbed with dye on the TiO2 photoanode. © Published by Elsevier Ltd. This © 2014 2014The TheAuthors. Authors. Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and/or peer-review under responsibility of ICAE Peer-review under responsibility of the Organizing Committee of ICAE2014 Keywords: Dye-sensitized solar cell; co-adsorbent; siloxane.
1. Introduction Due to the environmental concerns and the finite nature of fossil fuels, the development of alternative energy sources has become a subject of major research interest. It is envisioned that solar energy as one of the best candidates in this aspect. The prohibitive cost of silicon-based solar cells made them uncompetitive with conventional power generating methods [1]. The dye-sensitized solar cell (DSSC) has great potential for replacing traditional silicon solar cells because of its ease and low preparation cost [2]. The photoanode of a DSSC is typically made of a mesoporous TiO2 film [3] coated on a fluorine-doped tin oxide (FTO) conducting glass. A platinized FTO usually serves as the counter electrode. Typical electrolyte is an organic solvent containing the iodide/tri-iodide redox couple. The dyes anchored on the TiO2 surface absorbed incident visible light and generate excited electrons, these electrons being
* Corresponding author. Tel.: +886-2-26215656 ext. 2723; fax: +886-2-26209887. E-mail address: [email protected].
1876-6102 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Peer-review under responsibility of the Organizing Committee of ICAE2014 doi:10.1016/j.egypro.2014.11.978
Cheng-Lan Lin and Chun-Ming Chu / Energy Procedia 61 (2014) 842 – 845
transferred through the TiO2 to the outer circuits and the electricity is thus generated. The current generation ability is mostly determined by the excited electron-hole recombination rate (the electron life time) and the dark current of the DSSC, which correspond to the degree of aggregation of the absorbed dyes and the non-absorbed TiO2 surface. Co-absorbents of the dyes were therefore employed during the DSSC fabrication to address the aforementioned issues [4-7]. The development of convenient and effective co-absorbents is therefore important in improving the energy conversion efficiency of a DSSC. In this study, tetraethoxysilane (TEOS) or phenyltriethoxysilane (PTEOS) is used as the co-adsorbent with N719 dye to prepare the photoanode for a dye-sensitized solar cell (DSSC), and its effects on the photovoltaic performances of the DSSC are investigated. 2. Experimental Preparation of TiO2 photoanodes: 3g P25 was dispersed into 6 mL deionized water (DIW) containing 0.25 mL Acac. The mixture was stirred for 2 h, and PEG200k with 0.05 mL Triton-X100 were then added to the mixture. The mixture was stirred for an additional 24 h, and the TiO2 paste was thus obtained. The amount of TiO2 in the pastes was fixed at 15 wt% while the PEG/TiO2 ratio was 0.25 (w/w). FTO conducting glasses (7 Ω/sq.) were firstly cleaned by a neutral detergent solution, and then socinated sequentially with DIW, ethanol, acetone, IPA then DIW. Titanium isopropoxide was mixed with 2-ME at a ratio of 1/5 (w/w), and the solutions were then spin-coated onto clean FTO glasses and annealed at 450 o C for 30 min to form a thin TiO2 blocking layer. To prepare mesoporous TiO2 layer, the PEG200k/TiO2 paste was doctor-bladed onto the compact layer and then annealed at 450 oC for 30 min. The above procedure was repeated for three times. The photoanode was soaked in a 1:1 (v/v) mixture of ACN and tert-butyl alcohol containing 5×10-4 M N719 and different concentrations of TEOS or PTEOS coabsorbent at 80 oC for 12 h to obtain the photoanode. For the fabrication of DSSC, the dye-adsorbed TiO2 photoanode served as the working electrode, and a sputtered Platinum film on FTO glass was used as the counter electrode. A 60 μm-thick polyester tape was used as the spacer to separate the two electrodes. The electrolyte (an ACN solution containing 0.5 M LiI, 0.05 M I2, and 0.5 M 4-TBP) was injected into the aperture between the electrodes. Electrochemical measurements were performed by a CHI 760D potentiostat/galvanostat (CH Instrument, Inc.). 3. Results and Discussion Figure 1 shows the SEM images of the TiO2 photoanode and the TiO2 blocking layer. Mesoporous nanostructure of the photoanode can be clearly observed. A thin TiO2 blocking layer can be successfully prepared. Figure 2 shows the i-V curves and photovoltaic property comparisons of the DSSCs employing different concentrations of TEOS or PTEOS as the co-absorbent during the photoanode dye-absorbing process. Short-circuit current density, JSC, of the DSSCs increased as the TEOS or PTEOS was used as the co-adsorbent. Open-circuit voltage, VOC, of the DSSCs shifted toward more positive potential as the concentration of the TEOS or PTEOS used during the dye-absorbing process increased. Dark currents of the DSSCs using TEOS or PTEOS co-absorbent are all smaller than the one without co-absorbent. Fill factor, FF, of the DSSCs slightly decreased if TEOS or PTEOS was used as the co-absorbent. According to the above results, it is deduced that the TEOS or PTEOS should absorbed on the uncovered TiO2 surface, which reduced the rate of the excited electron-hole recombination and therefore increased the VOC of the DSSC. These co-absorbents might also reduced the aggregation degree of the
843
844
Cheng-Lan Lin and Chun-Ming Chu / Energy Procedia 61 (2014) 842 – 845
N719 dyes and thus enhanced the JSC of the DSSC. With 0.25 mM TEOS or 0.50 mM PTEOS used as the co-absorbent, energy conversion efficiency of the corresponding DSSC increased from 4.55 % to 4.97 % or 5.10%, respectively. Figure 3 shows the Nyquist plot and the Bode phase angle plot of the DSSCs using different concentrations of TEOS or PTEOS as the co-absorbent during the dye-absorbing process. The corresponding impedance values simulated form the Nyquist plots are listed in the table 1. R1 represent the charge transfer resistance at the electrolyte/platinum coounter electrode interface, R2 is the charge transfer resistance between the electrolyte and the TiO2 photoanode, R3 is the resistance of the ion diffusion in the electrolyte, and Rs is the serial resistance of the device including the FTO substrate and circuit. R2 remains similar for all of the DSSCs investigated and suggesting that the co-absorb of TEOS or PTEOS didn’t increased the charge transfer resistance at the TiO2/electrolyte interface. However, the characteristic peaks (at log(frequency) ~ 0.9) in the bode phase angle plots shifted toward smaller values with the increase of TEOS or PTEOS concentrations, indicating the increase of the electron life time in the TiO2 photoanode and therefore reduced the electron-hole recombination rates. The VOC of the DSSCs might thus being increased and the electrochemical impedance spectroscopy analysis consisted with the results obtained in the i-V curve measurements.
Fig. 1. SEM image of the (a) TiO2 photoanode and (b) TiO2 blocking layer. (c)
2
0 mM TEOS 0.25 mM TEOS 0.50 mM TEOS 0.75 mM TEOS 1 mM TEOS
4 0 -2 -4
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
8
0.74
7
VOC
Efficiency JSC
6
0.72
FF
5
0.70
4
0.68
0.00
Voltage (V)
0.25
0.50
0.75
1.00
10
0.78
2
8
2
0.76
VOC(V) and FF
6
(d)
10
Current density (mA/cm )
8
9
6
0 mM PTEOS 0.25 mM PTEOS 0.50 mM PTEOS 0.75 mM PTEOS 1 mM PTEOS
4 2 0 -2 -4
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
TEOS Concn. (mM)
9
0.76 Efficiency JSC
8
0.74
7
VOC
0.72
FF
6
0.70
5 4
0.00
Voltage (V)
0.25
0.50
0.75
VOC(V) and FF
0.78
2
Efficiency (%) and JSC(mA/cm )
2
Current density (mA/cm )
10
(b)
Efficiency (%) and JSC(mA/cm )
(a) 10
0.68
1.00
PTEOS Concn. (mM)
Fig. 2. i-V curves and photovoltaic property comparisons of the DSSCs employing different concentrations of TEOS ((a) and (b)) or PTEOS ((c) and (d)) as the co-absorbent during the photoanode dye-absorbing process.
4 3
0 mM TEOS 0.25 mM TEOS 0.50 mM TEOS 0.75 mM TEOS 1 mM TEOS
2 1 0 15
20
25
30
Z' (ohm)
35
(c)
6
-5 0
5 4 3
0 mM PTEOS 0.25 mM PTEOS 0.50 mM PTEOS 0.75 mM PTEOS 1 mM PTEOS
2 1
40
5 -1
0
1
2
3
log(frequence/Hz)
4
(d)
7
5
Phase (deg)
-10
-Z" (ohm)
6
8
0 mM TEOS 0.25 mM TEOS 0.50 mM TEOS 0.75 mM TEOS 1 mM TEOS
5
0 15
20
25
30
Z' (ohm)
35
40
-14 -12 -10 -8 -6 -4 -2 0 2 4 -1
0 mM PTEOS 0.25 mM PTEOS 0.50 mM PTEOS 0.75 mM PTEOS 1 mM PTEOS
(b)
-15
Phase (deg)
7
-Z" (ohm)
(a)
8
0
1
2
3
4
5
log(frequence/Hz)
Fig. 3. The Nyquist plots and the bode phase angle plots of the DSSCs employing different concentrations of TEOS ((a) and (b)) or PTEOS ((c) and (d)) as the co-absorbent during the photoanode dye-absorbing process.
845
Cheng-Lan Lin and Chun-Ming Chu / Energy Procedia 61 (2014) 842 – 845
4. Conclusions DSSCs using TEOS or PTEOS as the co-absorbent with the N719 dye were fabricated and their photovoltaic performances were investigated in this study. VOC and JSC of the DSSCs using TEOS or PTEOS as the co-absorbents were all increased compared to the DSSC without the co-absorbent. Electrochemical impedance spectroscopy analysis suggested that the electron life time was prolonged if these co-absorbent was employed in a DSSC. The energy conversion efficiency of the DSSCs were improved from 4.55 % to 4.97 % or 5.10 % if TEOS or PTEOS was used as the co-absorbent, respectively. The results suggested that these siloxanes might served as convenient and effective co-absorbents for the DSSCs. Table 1. Impedance properties of the DSSCs using TEOS or PTEOS co-absorbents estimated from the Nyquist polts. TEOS concn.
Rs
R1
R2
R3
PTEOS concn.
Rs
R1
R2
R3
(mM)
(ohm)
(ohm)
(ohm)
(ohm)
(mM)
(ohm)
(ohm)
(ohm)
(ohm)
0
19.17
2.53
13.54
0.36
0
19.17
2.53
13.54
0.36
0.25
20.10
2.41
13.52
0.38
0.25
19.80
2.62
12.37
0.32
0.50
19.61
2.93
12.00
0.34
0.50
18.91
2.82
12.14
0.33
0.75
20.29
2.84
13.06
0.52
0.75
19.12
2.91
13.45
0.33
1.00
19.28
2.73
13.96
0.36
1.00
20.09
2.55
11.97
0.34
References [1] Grätzel M. J Photochem Photobiol A Chem 2004; 164: 3-14. [2] O’Regan B, Grätzel M. Nature 1991; 353: 737-740. [3] Grätzel M. J Photochem Photobiol C Photochem Rev 2003; 4: 145-153. [4] Chen BS, Chen DY, Chen CL, Hsu CW, Hsu HC, Wu KL, Liu SH, Chou PT, Chi Y. J Mater Chem 2011; 21: 1937–1945. [5] Fan SQ, Kim CL, Fang BZ, Liao KX,Yang GJ, Li CJ, Kim JJ, Ko JJ. J Phys Chem C 2011; 115: 7747–7754. [6] Qu S, Wu W, Hua J, Kong C, Long Y, Tian H. J Phys Chem C 2010; 114,1343–1349. [7] llegrucci A, Lewcenko NA, Mozer AJ, Dennany L, Wagner P, Officer DL, Sunahara K, Moric S, Spiccia L. Energy Environ Sci 2009; 2: 1069–1073.
Biography Dr. Cheng-Lan Lin is an assistant professor of Department of Chemical and Materials Engineering at Tamkang University, Taiwan. His research interests include electrochemistry, fuel cell electrocatalysts, electrochromic materials and devices, and organic/inorganic hybrid materials.
ScienceDirect Energy Procedia 61 (2014) 842 – 845
The 6th International Conference on Applied Energy – ICAE2014
A Study on the Effects of Siloxane Derivatives as Coadsorbents on the Performance of Dye-Sensitized Solar Cells Cheng-Lan Lina,b,* and Chun-Ming Chua a
Department of Chemical and Materials Engineering, Tamkang University, 151 Yingzhuan Road, New Taipei City 25137, Taiwan b The Energy and Opto-Electronic Materials Research Center, Tamkang University, New Taipei City 25137, Taiwan
Abstract In this study, tetraethoxysilane (TEOS) or phenyltriethoxysilane (PTEOS) is used as the co-adsorbent with N719 dye to prepare the photoanode for a dye-sensitized solar cell (DSSC), and its effects on the photovoltaic performances of the DSSC are investigated. It is found that both the short-circuit current and the open-circuit voltage of the DSSC are increased with the co-adsorption of TEOS or PTEOS on the mesoporous TiO2 photoanode. Electrochemical impedance spectra indicate that the electron lifetime is improved. The energy conversion efficiency of the DSSC is promoted from 4.55 % to 4.97% or 5.10 %, respectively, when TEOS or PTEOS is co-adsorbed with dye on the TiO2 photoanode. © Published by Elsevier Ltd. This © 2014 2014The TheAuthors. Authors. Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and/or peer-review under responsibility of ICAE Peer-review under responsibility of the Organizing Committee of ICAE2014 Keywords: Dye-sensitized solar cell; co-adsorbent; siloxane.
1. Introduction Due to the environmental concerns and the finite nature of fossil fuels, the development of alternative energy sources has become a subject of major research interest. It is envisioned that solar energy as one of the best candidates in this aspect. The prohibitive cost of silicon-based solar cells made them uncompetitive with conventional power generating methods [1]. The dye-sensitized solar cell (DSSC) has great potential for replacing traditional silicon solar cells because of its ease and low preparation cost [2]. The photoanode of a DSSC is typically made of a mesoporous TiO2 film [3] coated on a fluorine-doped tin oxide (FTO) conducting glass. A platinized FTO usually serves as the counter electrode. Typical electrolyte is an organic solvent containing the iodide/tri-iodide redox couple. The dyes anchored on the TiO2 surface absorbed incident visible light and generate excited electrons, these electrons being
* Corresponding author. Tel.: +886-2-26215656 ext. 2723; fax: +886-2-26209887. E-mail address: [email protected].
1876-6102 © 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Peer-review under responsibility of the Organizing Committee of ICAE2014 doi:10.1016/j.egypro.2014.11.978
Cheng-Lan Lin and Chun-Ming Chu / Energy Procedia 61 (2014) 842 – 845
transferred through the TiO2 to the outer circuits and the electricity is thus generated. The current generation ability is mostly determined by the excited electron-hole recombination rate (the electron life time) and the dark current of the DSSC, which correspond to the degree of aggregation of the absorbed dyes and the non-absorbed TiO2 surface. Co-absorbents of the dyes were therefore employed during the DSSC fabrication to address the aforementioned issues [4-7]. The development of convenient and effective co-absorbents is therefore important in improving the energy conversion efficiency of a DSSC. In this study, tetraethoxysilane (TEOS) or phenyltriethoxysilane (PTEOS) is used as the co-adsorbent with N719 dye to prepare the photoanode for a dye-sensitized solar cell (DSSC), and its effects on the photovoltaic performances of the DSSC are investigated. 2. Experimental Preparation of TiO2 photoanodes: 3g P25 was dispersed into 6 mL deionized water (DIW) containing 0.25 mL Acac. The mixture was stirred for 2 h, and PEG200k with 0.05 mL Triton-X100 were then added to the mixture. The mixture was stirred for an additional 24 h, and the TiO2 paste was thus obtained. The amount of TiO2 in the pastes was fixed at 15 wt% while the PEG/TiO2 ratio was 0.25 (w/w). FTO conducting glasses (7 Ω/sq.) were firstly cleaned by a neutral detergent solution, and then socinated sequentially with DIW, ethanol, acetone, IPA then DIW. Titanium isopropoxide was mixed with 2-ME at a ratio of 1/5 (w/w), and the solutions were then spin-coated onto clean FTO glasses and annealed at 450 o C for 30 min to form a thin TiO2 blocking layer. To prepare mesoporous TiO2 layer, the PEG200k/TiO2 paste was doctor-bladed onto the compact layer and then annealed at 450 oC for 30 min. The above procedure was repeated for three times. The photoanode was soaked in a 1:1 (v/v) mixture of ACN and tert-butyl alcohol containing 5×10-4 M N719 and different concentrations of TEOS or PTEOS coabsorbent at 80 oC for 12 h to obtain the photoanode. For the fabrication of DSSC, the dye-adsorbed TiO2 photoanode served as the working electrode, and a sputtered Platinum film on FTO glass was used as the counter electrode. A 60 μm-thick polyester tape was used as the spacer to separate the two electrodes. The electrolyte (an ACN solution containing 0.5 M LiI, 0.05 M I2, and 0.5 M 4-TBP) was injected into the aperture between the electrodes. Electrochemical measurements were performed by a CHI 760D potentiostat/galvanostat (CH Instrument, Inc.). 3. Results and Discussion Figure 1 shows the SEM images of the TiO2 photoanode and the TiO2 blocking layer. Mesoporous nanostructure of the photoanode can be clearly observed. A thin TiO2 blocking layer can be successfully prepared. Figure 2 shows the i-V curves and photovoltaic property comparisons of the DSSCs employing different concentrations of TEOS or PTEOS as the co-absorbent during the photoanode dye-absorbing process. Short-circuit current density, JSC, of the DSSCs increased as the TEOS or PTEOS was used as the co-adsorbent. Open-circuit voltage, VOC, of the DSSCs shifted toward more positive potential as the concentration of the TEOS or PTEOS used during the dye-absorbing process increased. Dark currents of the DSSCs using TEOS or PTEOS co-absorbent are all smaller than the one without co-absorbent. Fill factor, FF, of the DSSCs slightly decreased if TEOS or PTEOS was used as the co-absorbent. According to the above results, it is deduced that the TEOS or PTEOS should absorbed on the uncovered TiO2 surface, which reduced the rate of the excited electron-hole recombination and therefore increased the VOC of the DSSC. These co-absorbents might also reduced the aggregation degree of the
843
844
Cheng-Lan Lin and Chun-Ming Chu / Energy Procedia 61 (2014) 842 – 845
N719 dyes and thus enhanced the JSC of the DSSC. With 0.25 mM TEOS or 0.50 mM PTEOS used as the co-absorbent, energy conversion efficiency of the corresponding DSSC increased from 4.55 % to 4.97 % or 5.10%, respectively. Figure 3 shows the Nyquist plot and the Bode phase angle plot of the DSSCs using different concentrations of TEOS or PTEOS as the co-absorbent during the dye-absorbing process. The corresponding impedance values simulated form the Nyquist plots are listed in the table 1. R1 represent the charge transfer resistance at the electrolyte/platinum coounter electrode interface, R2 is the charge transfer resistance between the electrolyte and the TiO2 photoanode, R3 is the resistance of the ion diffusion in the electrolyte, and Rs is the serial resistance of the device including the FTO substrate and circuit. R2 remains similar for all of the DSSCs investigated and suggesting that the co-absorb of TEOS or PTEOS didn’t increased the charge transfer resistance at the TiO2/electrolyte interface. However, the characteristic peaks (at log(frequency) ~ 0.9) in the bode phase angle plots shifted toward smaller values with the increase of TEOS or PTEOS concentrations, indicating the increase of the electron life time in the TiO2 photoanode and therefore reduced the electron-hole recombination rates. The VOC of the DSSCs might thus being increased and the electrochemical impedance spectroscopy analysis consisted with the results obtained in the i-V curve measurements.
Fig. 1. SEM image of the (a) TiO2 photoanode and (b) TiO2 blocking layer. (c)
2
0 mM TEOS 0.25 mM TEOS 0.50 mM TEOS 0.75 mM TEOS 1 mM TEOS
4 0 -2 -4
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
8
0.74
7
VOC
Efficiency JSC
6
0.72
FF
5
0.70
4
0.68
0.00
Voltage (V)
0.25
0.50
0.75
1.00
10
0.78
2
8
2
0.76
VOC(V) and FF
6
(d)
10
Current density (mA/cm )
8
9
6
0 mM PTEOS 0.25 mM PTEOS 0.50 mM PTEOS 0.75 mM PTEOS 1 mM PTEOS
4 2 0 -2 -4
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
TEOS Concn. (mM)
9
0.76 Efficiency JSC
8
0.74
7
VOC
0.72
FF
6
0.70
5 4
0.00
Voltage (V)
0.25
0.50
0.75
VOC(V) and FF
0.78
2
Efficiency (%) and JSC(mA/cm )
2
Current density (mA/cm )
10
(b)
Efficiency (%) and JSC(mA/cm )
(a) 10
0.68
1.00
PTEOS Concn. (mM)
Fig. 2. i-V curves and photovoltaic property comparisons of the DSSCs employing different concentrations of TEOS ((a) and (b)) or PTEOS ((c) and (d)) as the co-absorbent during the photoanode dye-absorbing process.
4 3
0 mM TEOS 0.25 mM TEOS 0.50 mM TEOS 0.75 mM TEOS 1 mM TEOS
2 1 0 15
20
25
30
Z' (ohm)
35
(c)
6
-5 0
5 4 3
0 mM PTEOS 0.25 mM PTEOS 0.50 mM PTEOS 0.75 mM PTEOS 1 mM PTEOS
2 1
40
5 -1
0
1
2
3
log(frequence/Hz)
4
(d)
7
5
Phase (deg)
-10
-Z" (ohm)
6
8
0 mM TEOS 0.25 mM TEOS 0.50 mM TEOS 0.75 mM TEOS 1 mM TEOS
5
0 15
20
25
30
Z' (ohm)
35
40
-14 -12 -10 -8 -6 -4 -2 0 2 4 -1
0 mM PTEOS 0.25 mM PTEOS 0.50 mM PTEOS 0.75 mM PTEOS 1 mM PTEOS
(b)
-15
Phase (deg)
7
-Z" (ohm)
(a)
8
0
1
2
3
4
5
log(frequence/Hz)
Fig. 3. The Nyquist plots and the bode phase angle plots of the DSSCs employing different concentrations of TEOS ((a) and (b)) or PTEOS ((c) and (d)) as the co-absorbent during the photoanode dye-absorbing process.
845
Cheng-Lan Lin and Chun-Ming Chu / Energy Procedia 61 (2014) 842 – 845
4. Conclusions DSSCs using TEOS or PTEOS as the co-absorbent with the N719 dye were fabricated and their photovoltaic performances were investigated in this study. VOC and JSC of the DSSCs using TEOS or PTEOS as the co-absorbents were all increased compared to the DSSC without the co-absorbent. Electrochemical impedance spectroscopy analysis suggested that the electron life time was prolonged if these co-absorbent was employed in a DSSC. The energy conversion efficiency of the DSSCs were improved from 4.55 % to 4.97 % or 5.10 % if TEOS or PTEOS was used as the co-absorbent, respectively. The results suggested that these siloxanes might served as convenient and effective co-absorbents for the DSSCs. Table 1. Impedance properties of the DSSCs using TEOS or PTEOS co-absorbents estimated from the Nyquist polts. TEOS concn.
Rs
R1
R2
R3
PTEOS concn.
Rs
R1
R2
R3
(mM)
(ohm)
(ohm)
(ohm)
(ohm)
(mM)
(ohm)
(ohm)
(ohm)
(ohm)
0
19.17
2.53
13.54
0.36
0
19.17
2.53
13.54
0.36
0.25
20.10
2.41
13.52
0.38
0.25
19.80
2.62
12.37
0.32
0.50
19.61
2.93
12.00
0.34
0.50
18.91
2.82
12.14
0.33
0.75
20.29
2.84
13.06
0.52
0.75
19.12
2.91
13.45
0.33
1.00
19.28
2.73
13.96
0.36
1.00
20.09
2.55
11.97
0.34
References [1] Grätzel M. J Photochem Photobiol A Chem 2004; 164: 3-14. [2] O’Regan B, Grätzel M. Nature 1991; 353: 737-740. [3] Grätzel M. J Photochem Photobiol C Photochem Rev 2003; 4: 145-153. [4] Chen BS, Chen DY, Chen CL, Hsu CW, Hsu HC, Wu KL, Liu SH, Chou PT, Chi Y. J Mater Chem 2011; 21: 1937–1945. [5] Fan SQ, Kim CL, Fang BZ, Liao KX,Yang GJ, Li CJ, Kim JJ, Ko JJ. J Phys Chem C 2011; 115: 7747–7754. [6] Qu S, Wu W, Hua J, Kong C, Long Y, Tian H. J Phys Chem C 2010; 114,1343–1349. [7] llegrucci A, Lewcenko NA, Mozer AJ, Dennany L, Wagner P, Officer DL, Sunahara K, Moric S, Spiccia L. Energy Environ Sci 2009; 2: 1069–1073.
Biography Dr. Cheng-Lan Lin is an assistant professor of Department of Chemical and Materials Engineering at Tamkang University, Taiwan. His research interests include electrochemistry, fuel cell electrocatalysts, electrochromic materials and devices, and organic/inorganic hybrid materials.