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Issue 46, 2010
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Enhanced open circuit voltage by hydrophilic ionic liquids as buffer layer in conjugated polymer–nanoporous titania hybrid solar cells

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Abstract

We demonstrate the fabrication of a nanoporous titania (NP-TiO2) network structure by using a polystylene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer template and modifying the surface of NP-TiO2 with ionic liquids (ILs), bmim-BF4 and benmim-Cl. The effect of the molecular weight of PS-b-P4VP on the morphology of the NP-TiO2 and IL-modified NP-TiO2 are characterized by scanning electron microscopy and contact angle measurements. Subsequently, hybrid solar cells are fabricated using MEH-PPV and NP-TiO2, and the effect of IL layers and IL concentrations on device performances are evaluated under AM 1.5 G illumination. The devices containing bmim-BF4 and benmim-Cl show drastically enhanced open circuit voltages (Voc) of 1.05 V and 0.91 V, respectively, while the reference device without an IL layer exhibits a Voc of 0.60 V. Significantly improved Voc can be attributed to the change in interfacial energy levels by formation of ionic double layers at the TiO2/IL and at the IL/MEH-PPV interfaces. We also observed the trend that short circuit current decreased and Voc increased with increasing IL concentration, which is ascribed to interruption of charge transfer from MEH-PPV to TiO2 and the change in interfacial energy level by shifting the vacuum level, respectively.

Graphical abstract: Enhanced open circuit voltage by hydrophilic ionic liquids as buffer layer in conjugated polymer–nanoporous titania hybrid solar cells

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Publication details

The article was received on 08 Sep 2010, accepted on 04 Oct 2010 and first published on 26 Oct 2010


Article type: Paper
DOI: 10.1039/C0CP01754J
Citation: Phys. Chem. Chem. Phys., 2010,12, 15309-15314
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    Enhanced open circuit voltage by hydrophilic ionic liquids as buffer layer in conjugated polymer–nanoporous titania hybrid solar cells

    H. Choi, H. Cho, S. Song, H. Suh, S. Park and J. Y. Kim, Phys. Chem. Chem. Phys., 2010, 12, 15309
    DOI: 10.1039/C0CP01754J

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