Supramolecular Photovoltaic Cells Based on Composite Molecular Nanoclusters:  Dendritic Porphyrin and C₆₀, Porphyrin Dimer and C₆₀, and Porphyrin−C₆₀Dyad

Abstract

Novel organic solar cells have been prepared using molecular clusters of porphyrin dendrimer (donor) and fullerene (acceptor) dye units assembled on SnO2 electrodes. The molecular clusters of porphyrin with dendritic structure and fullerene exhibit controlled size and shape in contrast with the reference systems (a porphyrin dimer and a porphyrin−fullerene dyad) without dendritic structure in TEM images, which show rather irregular and smaller clusters. The composite molecular nanoclusters of dendritic porphyrin and fullerene prepared in acetonitrile/toluene mixed solvent absorb light over entire spectrum of visible light. The comparison of photoelectrochemical properties of composite molecular cluster of porphyrin and fullerene with that of molecular cluster of porphyrin−C60 dyad with covalent linkage shows the importance of interpenetrating structure in each network to transport hole and electron efficiently. Furthermore, organic photovoltaic cells using clusters of supramolecular complexes of V-shaped porphyrin dimer and porphyrin dendrimers with fullerene exhibit remarkable enhancement in the photoelectrochemical performance as well as broader photoresponse in the visible and near-infrared regions as compared with the reference system. This clearly indicates that the π−π interaction between porphyrins and fullerenes in the supramolecular clusters plays an important role in improving the light energy conversion efficiency.

Creation of Fullerene-Based Artificial Photosynthetic Systems

“…We have extended the concept of dye-sensitized bulk heterojunction solar cells into more sophisticated supramolec- ular systems prepared using bottom-up self-organization of porphyrin and fullerene with dendrimers 109,110 and nanoparticles 108,111-116 on a SnO 2 electrode. In particular, porphyrinalkanethiol 17 (n: number of the methylene groups in the alkanethiol; n ¼ 5, 11, and 15) 156 are three-dimensionally organized onto a gold nanoparticle with a diameter of %2 nm to give multiporphyrin-modified gold nanoparticles 18 (n ¼ 5, 11, and 15) [199][200][201][202] with well-defined size (%10 nm) and spherical shape (step 1 in Scheme 6).…”

Relationship between Incoherent Excitation Energy Migration Processes and Molecular Structures in Zinc(II) Porphyrin Dendrimers

“…In this context, there have been tremendous efforts to mimic the natural photosynthetic system for the realization of highly efficient molecular photonic devices such as molecular wires, switches, transistors, and artificial light-harvesting devices. [4][5][6][7][8][9][10][11] The 96 chlorophyll units in cyanobacterial photosystem I (PSI) are congested and three-dimensionally arranged in a protein matrix. [1] Compared with the well-ordered anoxygenic photosynthetic light-harvesting complex, it is unclear why the disordered and randomly oriented geometry of oxygenic PSI was chosen by nature.…”

Photoresponsive Arylether Dendrimers with Azobenzene Core and Terminal Vinyl Groups

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Dendrimers with photoresponsive moiety at the core or the branch or the periphery may play an important role in nanotechnology including the preparation of functional nanomaterials such as nano-sized molecular electronic device, molecular photoswitch, sensor, and drug-delivery systems because light-driven simple geometrical change of core molecule or concurrent geometrical changes of many peripheral molecules may result in the large conformational change throughout the dendritic entity. [19][20][21][22] Azobenzene is well known photochromic molecule to show clean reversible isomerization. [23][24][25][26] The more stable trans-azobenzene can be converted to the less stable cisazobenzene by UV light irradiation.…”