Details

Autor(en) / Beteiligte

• Benson-Smith, J. J.
• Goris, L.
• Vandewal, K.
• Haenen, K.
• Manca, J. V.
• Vanderzande, D.
• Bradley, D. D. C.
• Nelson, J.

Titel

Formation of a Ground-State Charge-Transfer Complex in Polyfluorene//[6,6]-Phenyl-C61 Butyric Acid Methyl Ester (PCBM) Blend Films and Its Role in the Function of Polymer/PCBM Solar Cells

Ist Teil von

• Advanced functional materials, 2007-02, Vol.17 (3), p.451-457

Ort / Verlag

Weinheim: WILEY-VCH Verlag

Erscheinungsjahr

2007

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Evidence is presented for the formation of a weak ground‐state charge‐transfer complex in the blend films of poly[9,9‐dioctylfluorene‐co‐N‐(4‐methoxyphenyl)diphenylamine] polymer (TFMO) and [6,6]‐phenyl‐C61 butyric acid methyl ester (PCBM), using photothermal deflection spectroscopy (PDS) and photoluminescence (PL) spectroscopy. Comparison of this polymer blend with other polyfluorene polymer/PCBM blends shows that the appearance of this ground‐state charge‐transfer complex is correlated to the ionization potential of the polymer, but not to the optical gap of the polymer or the surface morphology of the blend film. Moreover, the polymer/PCBM blend films in which this charge‐transfer complex is observed also exhibit efficient photocurrent generation in photovoltaic devices, suggesting that the charge‐transfer complex may be involved in charge separation. Possible mechanisms for this charge‐transfer state formation are discussed as well as the significance of this finding to the understanding and optimization of polymer blend solar cells. A low‐energy absorption band is observed in the absorption spectrum of a polyfluorene/fullerene blend film (see figure) and is assigned to a weak charge‐transfer complex (CTC). The presence of this CTC state is correlated to efficient charge separation and photocurrent generation in photovoltaic devices.