Molecular Structure Effect of Pyridine-Based Surface Ligand on the Performance of P3HT:TiO2 Hybrid Solar Cell

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• 作者：Jhih-Fong Lin ; Guang-Yao Tu ; Chun-Chih Ho ; Chun-Yu Chang ; Wei-Che Yen ; Sheng-Hao Hsu ; Yang-Fang Chen ; Wei-Fang Su
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2013
• 出版时间：February 13, 2013
• 年：2013
• 卷：5
• 期：3
• 页码：1009-1016
• 全文大小：462K
• 年卷期：v.5,no.3(February 13, 2013)
• ISSN：1944-8252

文摘

Colloid TiO₂ nanorods are used for solution-processable poly(3-hexyl thiophene): TiO₂ hybrid solar cell. The nanorods were covered by insulating ligand of oleic acid (OA) after sol-gel synthesis. Three more conducting pyridine type ligands: pyridine, 2,6-lutidine (Lut) and 4-tert-butylpyridine (tBP) were investigated respectively to replace OA. The power conversion efficiency (PCE) of the solar cell was increased because the electronic mobility of pyridine-type ligand-modified TiO₂ is higher than that of TiO₂鈥揙A. The enhancement of PCE is in the descending order of Lut > pyridine > tBP because of the effective replacement of OA by Lut. The PCE of solar cell can be further enhanced by ligand exchange of pyridine type ligand with conjugating molecule of 2-cyano-3-(5-(7-(thiophen-2-yl)-benzothiadiazol-4-yl) thiophen-2-yl) acrylic acid (W4) on TiO₂ nanorods because W4 has aligned bandgap with P3HT and TiO₂ to facilitate charge separation and transport. The electronic mobility of two-stage ligand exchanged TiO₂ is improved furthermore except Lut, because it adheres well and difficult to be replaced by W4. The amount of W4 on TiO₂-tBP is 3 times more than that of TiO₂鈥揕ut (0.20 mol % vs. 0.06 mol %). Thus, the increased extent of PCE of solar cell is in the decreasing order of tBP > pyridine > Lut. The TiO₂-tBP-W4 device has the best performance with 1.4 and 2.6 times more than TiO₂-pyridine-W4 and TiO₂-Lut-W4 devices, respectively. The pKa of the pyridine derivatives plays the major role to determine the ease of ligand exchange on TiO₂ which is the key factor mandating the PCE of P3HT:TiO₂ hybrid solar cell. The results of this study provide new insights of the significance of acid-base reaction on the TiO₂ surface for TiO₂-based solar cells. The obtained knowledge can be extended to other hybrid solar cell systems.

Keywords:

polymer; nanoparticle; surface modifier; ligand exchange; hybrid solar cell; power conversion efficiency