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Abstract:
Efficient synthesis of a series of terminally dicyanovinyl (DCV)-substituted
oligothiophenes, DCVnT 1-6, without solubilizing side chains synthesized via
a novel convergent approach and their application as electron donors in
vacuum-processed m-i-p-type planar and p-i-n-type bulk heterojunction
organic solar cells is described. Purification of the products via gradient
sublimation yielded thermally highly stable organic semiconducting materials
in single crystalline quality which allowed for X-ray structure analysis.
Important insight in the packing features and intermolecular interactions of
these promising solar cell materials are provided. Optical absorption
spectra and electrochemical properties of the oligomers were investigated
and valuable structure-property relationships deduced. Photovoltaic devices
incorporating DCVnTs 4-6 showed power conversion efficiencies up to 2.8% for
planar and 5.2% for bulk heterojunction organic solar cells under full sun
illumination (mismatch corrected simulated AM 1.5G sunlight). The 5.2%
efficiency shown here represents one of the highest values ever reported for
organic vacuum-deposited single heterojunction solar cells.