Orawan Wiranwetchayan, Zhiqiang Liang, Qifeng Zhang, Guozhong Cao, Pisith Singjai
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DOI: 10.4236/msa.2011.212226   PDF    HTML     6,104 Downloads   11,681 Views   Citations

Abstract

The role of wide band gap oxide thin layer in inverted structure polymer solar cells was investigated by employing oxide films of TiO₂ and Nb₂O₅approximately 10 nm in thickness deposited onto FTO substrates. The experimental results demonstrated that the thin oxide layer serving to separate the electron collecting electrode and the photoactive film of a blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) was necessary to promote the formation of continuous uniform PCBM film to block holes in P3HT from being recombined with electrons in collecting electrode. A use of TiO₂ buffer layer leads to power conversion efficiency as high as 2.8%. As for Nb₂O₅, in spite the fact that its conduction band is higher than the LUMO level of PCBM polymer acting as electron transport material, a power conversion of 2.7%, which was only slightly different from the 2.8% achieved for the cell employing TiO₂. These experimental results suggest a tunneling mechanism for the electrons to transport from the PCBM to collecting electrode over the oxide film, instead of a diffusion through the oxide film arising from either energy or concentration difference of the photogenerated electrons.

Keywords

Polymer Solar Cell, Oxide Thin Film, TiO₂ Thin Film, Nb₂O₅ Thin Film

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Conflicts of Interest

The authors declare no conflicts of interest.

References

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