Molecular structure effect of pyridine-based surface ligand on the performance of P3HT:TiO 2 hybrid solar cell

Jhih Fong Lin, Guang Yao Tu, Chun Chih Ho, Chih Yu Chang, Wei Che Yen, Sheng Hao Hsu, Yang Fang Chen, Wei Fang Su

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Abstract

Colloid TiO 2 nanorods are used for solution-processable poly(3-hexyl thiophene): TiO 2 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 TiO 2 is higher than that of TiO 2 -OA. 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 TiO 2 nanorods because W4 has aligned bandgap with P3HT and TiO 2 to facilitate charge separation and transport. The electronic mobility of two-stage ligand exchanged TiO 2 is improved furthermore except Lut, because it adheres well and difficult to be replaced by W4. The amount of W4 on TiO 2 -tBP is 3 times more than that of TiO 2 -Lut (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 TiO 2 -tBP-W4 device has the best performance with 1.4 and 2.6 times more than TiO 2 -pyridine-W4 and TiO 2 -Lut-W4 devices, respectively. The pKa of the pyridine derivatives plays the major role to determine the ease of ligand exchange on TiO 2 which is the key factor mandating the PCE of P3HT:TiO 2 hybrid solar cell. The results of this study provide new insights of the significance of acid-base reaction on the TiO 2 surface for TiO 2 -based solar cells. The obtained knowledge can be extended to other hybrid solar cell systems.

Original languageEnglish
Pages (from-to)1009-1016
Number of pages8
JournalACS Applied Materials and Interfaces
Volume5
Issue number3
DOIs
Publication statusPublished - Feb 13 2013
Externally publishedYes

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Keywords

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

ASJC Scopus subject areas

  • Materials Science(all)

Cite this

Lin, J. F., Tu, G. Y., Ho, C. C., Chang, C. Y., Yen, W. C., Hsu, S. H., Chen, Y. F., & Su, W. F. (2013). Molecular structure effect of pyridine-based surface ligand on the performance of P3HT:TiO 2 hybrid solar cell. ACS Applied Materials and Interfaces, 5(3), 1009-1016. https://doi.org/10.1021/am302700c