Tetrafullerene Conjugates for All-Organic Photovoltaics

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• 作者：Gustavo Fern&aacute ; ndez ; Luis S&aacute ; nchez ; Dirk Veldman ; Martijn M. Wienk ; Carmen Atienza ; Dirk M. Guldi ; René ; A. J. Janssen ; Nazario Mart&iacute ; n
• 刊名：Journal of Organic Chemistry
• 出版年：2008
• 出版时间：April 18, 2008
• 年：2008
• 卷：73
• 期：8
• 页码：3189 - 3196
• 全文大小：365K
• 年卷期：v.73,no.8(April 18, 2008)
• ISSN：1520-6904

文摘

The synthesis of two new tetrafullerene nanoconjugates in which four C₆₀ units are covalently connectedthrough different images/gifchars/pi.gif" BORDER=0 >-conjugated oligomers (oligo(p-phenylene ethynylene) and oligo(p-phenylene vinylene))is described. The photovoltaic (PV) response of these C₆₀-based conjugates was evaluated by using themas the only active material in organic solar cells, showing a low PV performance. Photophysical studiesin solution demonstrated a very fast (~10 ps) deactivation of the singlet excited state of the central coreunit to produce both charge-separated species (i.e., C₆₀^{images/entities/bull.gif">-}-oligomer^{+images/entities/bull.gif">}-(C₆₀)₃ and C₆₀ centered singletexcited states). The charge-separated state recombines partly to the C₆₀ centered singlet state that undergoessubsequent intersystem crossing. Photophysical studies carried out in films support these data, exhibitinglong-lived triplet excited states. For both tetrafullerene arrays, the low yield of long-lived charge carriersin thin films accounts for the limited PV response. On the contrary, utilizing the oligo(p-phenylenevinylene) centered precursor aldehyde as an electron donor and antennae unit and mixing with the well-known C₆₀ derivative PCBM, the photophysical studies in films show the formation of long-lived charges.The PV devices constructed from these mixtures showed a relatively high photocurrent of 2 mA cm^-2.The sharp contrast between the nanoconjugates and the physical blends tentatively was attributed toimproved charge dissociation and the collection of more favorable energy levels in the blends as a resultof partial aggregation of both of the components.