A Study on the Dye-Sensitized Solar Cells and Donor Acceptor Chromophores as a Novel Sensitizer
Date Issued
2005
Date
2005
Author(s)
Huang, Chung-Yi
DOI
zh-TW
Abstract
The research work on dye-sensitized solar cells (DSSCs) has been progressed rapidly since 1991 by Prof. Grätzel’s group. DSSC, a novel type of solar cell, can harvest visible light energy for the generation of electricity by a dye sensitizer, which is adsorbed on TiO2 particles, and the efficiency of DSSCs can reach about 10~11%. Their efficiency is very comparable with that of the amorphous silicon solar cell. In order to optimize the performance of DSSCs, various hydrothermal temperatures and thicknesses of TiO2 were investigated in this study. Further, the effects of counter electrode, active area, and substrates’ conductivity on the efficiency were also explored. In addition, electrochemical impedance spectroscopy (EIS) was used to analyze internal resistances of the DSSCs. Finally, few novel sensitizers such as hybrid choromophores were synthesized and fabricated in photovoltaic devices for improving their efficiency.
The effects of hydrothermal temperature in preparing TiO2 and film thickness on the performance of DSSCs were investigated. The pore diameter and surface area of TiO2 played important roles in determining the cell efficiency. The TiO2 film in the DSSC must provide enough surface area to adsorb sufficient dyes, while an adequate pore size is required to facilitate the transport of the redox couple. When autoclaving temperature was increased from 180 ℃to 260 ℃, it was found that the pore diameters increased from 7.1 nm to 15.7 nm, and surface area decreased from 111.3 m2/g to 63.8 m2/g.
The results revealed that DSSCs made with TiO2 films prepared under hydrothermal temperature of 240 ℃, and film thickness of larger than 10 mm possessed the optimal performance. This result can be explained by the reported lifetime of photo-injected electrons. EIS was also used to analyze internal resistance, which was affected by the thickness of the TiO2 thin film. EIS results also support an earlier observation that the thickness of the TiO2 film would be greater than 10 mm.
When the sputtering time of Pt (counter electrode) was 30 min, the resistance of the device had been decreased. The sheet resistance of FTO also had some influences on fill factor (FF). On other hand, when the active area was 0.25 cm2, the cell would have less IR drop and a better value on FF. By using 0.25 cm2 as the active area with the FTO sheet resistance of 7 ohm/sq., the cell efficiency would reach to 7.97%, and the value of VOC, Isc, and FF were 0.69 V, 4.53 mA and 0.64, respectively.
The at-rest stability of the DSSC for over 200 days was monitored; At the end of this peroid, the value of VOC varied from 0.61 V to 0.56 V, JSC decreased from 1.30 mA/cm2 to 0.93 mA/cm2, and the efficiency reduced from 5.0% initially to 3.0% This may be due to the sealing imperfection and impurity, such as water and oxygen, which may react with the sensitizer.
Hybrid donor-acceptor choromophores can also work as the sensitizers, where the efficiency could reach about 1.26% Even though this efficiency is not comparable with N3 dye, it provides an alternative for the organic dyes in harvesting the light energy using DSSCs.
Subjects
染料敏化太陽能電池
水熱溫度
交流阻抗法
導電玻璃
能量轉移
施體-受體發光團
DSSC
Hydrothermal temperature
Electrochemical impedance spectroscopy
Conductive glass
Energy transfer
Hybrid choromophores
SDGs
Type
thesis
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