Organic solar cells. Supramolecular composites of porphyrins and fullerenes organized by polypeptide structures as light harvesters

Taku Hasobe, Kenji Saito, Prashant V. Kamat, Vincent Troiani, Hongjin Qiu, Nathalie Solladié, Kil Suk Kim, Jong Kang Park, Dongho Kim, Francis D'Souza, Shunichi Fukuzumi

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151 Scopus citations


We have constructed supramolecular solar cells composed of a series of porphyrin-peptide oligomers [porphyrin functionalized α-polypeptides, P(H2P)n or P(ZnP)n (n = 1, 2, 4, 8, 16)], and fullerenes assembled on a nanostructured SnO2 electrode using an electrophoretic deposition method. Remarkable enhancement in the photoelectrochemical performance as well as the broader photoresponse in the visible and near-infrared regions is seen with increasing the number of porphyrin units in α-polypeptide structures. Formation of supramolecular clusters of porphyrins and fullerenes prepared in acetonitrile-toluene = 3: 1 has been confirmed by transmission electron micrographs (TEM) and the absorption spectra. The highly colored composite clusters of porphyrin-peptide oligomers and fullerenes have been assembled as three-dimensional arrays onto nanostructured SnO2 films using an electrophoretic deposition method. A high power conversion efficiency (η) of ∼1.6% and the maximum incident photon-to-photocurrent efficiency (IPCE = 56%) were attained using composite clusters of free base and zinc porphyrin-peptide hexadecamers [P(H2P)16 and P(ZnP)16] with fullerenes, respectively. Femtosecond transient absorption and fluorescence measurements of porphyrin-fullerene composite films confirm improved electron-transfer properties with increasing number of porphyrins in a polypeptide unit. The formation of molecular assemblies between porphyrins and fullerenes with a polypeptide structure controls the electron-transfer efficiency in the supramolecular complexes, meeting the criteria required for efficient light energy conversion.

Original languageEnglish
Pages (from-to)4160-4170
Number of pages11
JournalJournal of Materials Chemistry
Issue number39
StatePublished - 2007


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