二氧化鈦奈米管複合高分子固態電解質之染料敏化太陽能電池

Binary (Poly(vinylidenefluoride-co- hexafluoropropylene)/ titanium oxide nanotube Solid-State Redox Electrolyte for Dye-sensitized solar cells

陳育萱(Yu-Hsuan Chen)

指導教授 ： 諸柏仁

國立中央大學/理學院/化學系/碩士(2008年)

摘要

染料敏化太陽能電池之固態電解質有助於發展穩定性高的電池元件，用以改善液態電解質容易揮發洩液及無法大面積使用等缺點
。在本研究中主要利用聚二氟乙烯-六氟丙烯共聚高分子（PVdF-HFP
)與二氧化鈦奈米管（Titanium oxide -nanotube）摻合製備高分子固態氧化還原對電解質，其複合高分子電解質薄膜所測量出的離子導電度優於文獻上所報導的高分子電解質薄膜導電度甚至趨近於液態電解質導電度。
二氧化鈦奈米管的添加有助於鹽類 LiI 的解離，因為 Li+ 與 TiNT 結構表面之間有作用力，會以 Lithium Anatase 或 Lithium Titanate 形式存在。由 DSC、AC-impedance 研究結果顯示，TiNT 的添加可以阻礙 I2 的結晶，幫助鹽類解離，形成離子複合物（Li+
/I3-）及可移動的離子（I-/I3-）。當高含量 TiNT 引入電解質時，解離的離子可能會 trap 在其結構上，限制離子移動而降低離子導電度， 最佳的 TiNT 添加量為重量比3 (w/w)。在SEM 的表面型態觀察上，可看見薄膜中有機/無機物均勻混合，無相分離現象產
生，而高分子 PVdF-HFP 的多孔性結構則有助於幫助保存離子液體與微量有機溶劑。
在本研究電解質系統，高分子 PVdF-HFP 與 TiNT 分別與鹽類都有作用力存在，因而降低 PVdF-HFP 的結晶度，使非結晶區域增加。高分子在電解質中提供一個流暢的路徑，使氧化還原對（I-/I3
-）能沿著具方向性的二
氧化鈦奈米管表面進行 ion exchange mechanism，在未使用液態電解質的情況下能提升離子導度。PVdF-HFP / LiI / I2 / TiNT 電解質比例為2:8:1:3 時，離子導電度可高達6.28× 10-2 S/cm。在電池元件部分，電解質比例為0:8:1:3時，光電轉換效率最高可以達到5.13%。

關鍵字

染敏太陽能電池 ； 二氧化鈦奈米管 ； 高分子固態電解質

並列摘要

Solvent free dye sensitized solar cell (DSSC) is a criti-
calstep towards a durable solar cell. In this paper, the solid state redox electrolyte of photoelectronchemical cells base on (Poly(vinylidenefluoride-co-hexafluoropro-
pylene) / Titanium oxide nanotube (TiNT) composite polymer electrolyteconfirmed that a solvent free electrolyte can yield the ion conductivity comparable or surpassing that of
a liquid or gel electrolyte.
In presence of TiNT, LiI salt is fully dissociated due to
the strong lithium association with TiNT in the Lithium Anatase, and Lithium Titanate forms. The complexation structure depends heavily on the degree of dissociation of LiI on the TiO2 substrate surface. Presence of TiNT,induces
large amount of Li+/I3- complex formation, facilitating electron transport by the ion exchange mechanism. This is evident from the reduction of the crystalline I2 in the LiI
/I2/TiNT system by DSC、AC-impedance. While high content of
TiNT that the dissociated ion are not all contributing toward ion conductivity. In presence of TiNT , these ions may be trapped render it less mobile. The best balance between high ionic dissociation and high ion motion is reached at TiNT at 3 part. As evident from SEM micrograph, PVdF-HFP / TiNT become miscible in presence of the salt. The result is the formation of homogeneous and mechanical-
ly tough membrane.
On the other hand, although PVdF-HFP degree of crystallin
-ity is hindered in presence of salt and TiNT, which suggested close interaction of the ionic liquid with the polymer,ionic mobility is not improved solely by PVdF-HFP.
This is commonly accepted to be due to the bulky nature of the anion. However, with the addition of TiNT to form composite with PVdF-HFP,ion pairing (Li+ I3-) is largely suppressed by TiNT and enhanced the dissociation of the I-
/I3- redox couple. Here the PVdF-HFP (now totally amorphous
)polymer provided a fluent path way to mobilize the fully dissociated ionic species along the more directional TiNT surface, thus an elevated ion conductivity can be reached without the use of solvent. The highest ion conductivity of 6.28×10-2 S/cm is detected at the optimized composition of 2:8:1:3 composition. The best photoelectric conversion efficiency（η）of 5.13% under illumination of simulated AM 1.5 (100mWcm-2).

並列關鍵字

polymer solid el ； PVdF-HFP ； titania nano tube(TNT)

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