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

Abstract

We have constructed supramolecular solar cells composed of a series of porphyrin-peptide oligomers [porphyrin functionalized a-polypeptides, P(H 2 P) n or P(ZnP) n (n = 1, 2, 4, 8, 16)], and fullerenes assembled on a nanostructured SnO 2 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 a-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 threedimensional arrays onto nanostructured SnO 2 films using an electrophoretic deposition method. A high power conversion efficiency (g) of y1.6% and the maximum incident photon-tophotocurrent efficiency (IPCE = 56%) were attained using composite clusters of free base and zinc porphyrin-peptide hexadecamers [P(H 2 P) 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.

Porphyrin polymers and organic frameworks

“…39(h)). 110 In this system the porphyrin was attached to the side chain of the polypeptide structure allowing for efficient organization of the electron-accepting fullerenes and porphyrins within the bulk of the photoactive layer. Although it was not clear what carrier mobilities could be obtained from this configuration, the work successfully demonstrated the importance of the molecular arrangement between the n-and p-type materials in the blended heterojunction.…”

Novel Electron Donor Acceptor Nanocomposites

“…Accordingly, the fabrication of donor-fullerene composites onto electrodes is a vital step for controlling the morphology of the composite assemblies on the electrode surface in molecular scale. Versatile methods such as Langmuir-Blodgett (LB) films [76], selfassembled monolayers (SAM) [77][78][79][80][81][82][83][84][85], layer-by-layer deposition [86,87], vacuum deposition [88,89], electrophoretic deposition [90][91][92][93][94][95][96][97][98][99], chemical adsorption, and spin coating [100][101][102][103][104][105][106][107], have been adopted to fabricate photoelectrochemical devices and solar cells.…”

Effect of Fullerene on Photocurrent Performance of 6‐O‐Porphyrin‐2,3‐di‐O‐stearoylcellulose Langmuir‐Blodgett Films

“…Hasobe et al pointed out that there are two essential factors in the efficient photocurrent generation: one is the charge separation between the porphyrin and C 60 , and the other is the resulting hole and electron transport in the film. [32] It would be reasonable, therefore, to attribute most of C 60 molecules in the cellulose LB films to the electron carriers that receive electrons, so that C 60 mediates the electron flow from H 2 Q in the electrolyte solution to the ITO electrode via the photoexcitation of porphyrins. Figure S3 shows action spectra of the ZnPCS-C 60 LB monolayer films.…”

“…Another and attractive approach would be the spontaneous complexation of pristine fullerene with the sandwich-like bisporphyrin [24][25][26] and multiporphyrin [27][28][29] host molecules via a p-p interaction. Among others, Hasobe et al have capitalized on the molecular recognition between porphyrins and fullerenes to prepare organic solar cells using porphyrin-coated gold nanoparticles [30] and porphyrinpolypeptide-coated SnO 2 nanoparticles [31,32] incorporating fullerenes. Although a variety of porphyrin-fullerene p-p stacking systems have been reported, those in the monolayer at the air-water interface or in the LB films are unprecedented.…”