Two-fold efficiency increase in nanocrystalline-TiO<sub>2</sub>/polymer photovoltaic devices by interfacial modification with a lithium salt

D. Aaron R. Barkhouse; Michelle J. Carey; Zhibin Xie; Kiril R. Kirov; Bernard M. Henry; Hazel E. Assender; Graham R. Webster; Paul L. Burn

doi:10.1117/12.679424

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3 November 2006 Two-fold efficiency increase in nanocrystalline-TiO₂/polymer photovoltaic devices by interfacial modification with a lithium salt

D. Aaron R. Barkhouse, Michelle J. Carey, Zhibin Xie, Kiril R. Kirov, Bernard M. Henry, Hazel E. Assender, Graham R. Webster, Paul L. Burn

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Proceedings Volume 6334, Organic Photovoltaics VII; 63340N (2006) https://doi.org/10.1117/12.679424
Event: SPIE Optics + Photonics, 2006, San Diego, California, United States

Abstract

Modification of the interface of titanium dioxide/poly[2-(2-ethylhexyloxy)-5-methoxy-1,4,-phenylenevinylene] (TiO₂/MEH-PPV) nanocomposite photovoltaic devices with a lithium salt, Li[CF₃SO₂]₂N, is shown to result in a twofold increase in device efficiency. The devices are of the type ITO/TiO₂/MEH-PPV/Au. The TiO₂ layer is deposited by doctor blading a colloidal anatase paste, and the polymer is then spin-coated on top followed by thermal evaporation of gold contacts. Careful control of manufacturing conditions and use of a 35 nm polymer layer leads to a device efficiency of 0.48% for un-modified devices. The increased efficiency following Li treatment is the result of a 40% increase in both the short-circuit current and fill factor, while the open-circuit voltage remains unchanged. A maximum efficiency of 1.05% has been achieved under 80% sun illumination. This represents a record efficiency for this type of cell. Photoconductivity experiments show a substantial increase in conductivity of the TiO₂ layer following Li modification. Interfacial modification is done via a simple soaking procedure, and the effect of varying the concentration of Li[CF₃SO₂]₂N is discussed. We report investigations into optimization and the mechanism of such improvement, for example by varying processing parameters of the modification procedure or the ionic species themselves.

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D. Aaron R. Barkhouse, Michelle J. Carey, Zhibin Xie, Kiril R. Kirov, Bernard M. Henry, Hazel E. Assender, Graham R. Webster, and Paul L. Burn "Two-fold efficiency increase in nanocrystalline-TiO₂/polymer photovoltaic devices by interfacial modification with a lithium salt", Proc. SPIE 6334, Organic Photovoltaics VII, 63340N (3 November 2006); https://doi.org/10.1117/12.679424

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