Keio University · Materials Science
Professor Taku Hasobe's research lab specializes in the design and fabrication of advanced nanomaterials for renewable energy applications, particularly in organic photovoltaics and light-harvesting systems. The lab focuses on supramolecular organization of porphyrins, fullerenes, and carbon nanomaterials (such as SWCNTs and graphene oxide) to create hierarchical, photoactive architectures that enable efficient light absorption, charge separation, and electron transport. By leveraging self-assembly, covalent functionalization, and nanostructured electrodes, the group develops highly efficient, solution-processable solar cells with enhanced photoelectrochemical performance. Their work bridges molecular engineering, nanomaterial science, and renewable energy technology.
Figures are computed from collected data and may differ slightly.
Novel organic solar cells have been prepared using quaternary self-organization of porphyrin (donor) and fullerene (acceptor) units by clusterization with gold nanoparticles on nanostructured SnO2 electrodes. First, porphyrin-alkanethiolate monolayer-protected gold nanoparticles (H2PCnMPC: n is the number of methylene groups in the spacer) are prepared (secondary organization) starting from the primary component (porphyrin-alkanethiol). These porphyrin-modified gold nanoparticles form complexes
The successful covalent functionalization of graphene oxide (GO) with 5-(4-aminophenyl)-10,15,20-triphenyl-21,23H-porphyrin (H2P) has been reported. The resulting GO–H2P hybrid material forms stable dispersions in DMF and has been thoroughly characterized by spectroscopic (UV-vis, ATR-IR, Raman) and thermal (TGA) tools. Microscopy techniques (AFM and TEM) have been employed to probe the morphological characteristics as well as to investigate the exfoliation of graphene sheets. Steady-state and t
Recent developments in synthetic and supramolecular techniques have made it possible to control precisely, organize and arrange molecules at the nanometre level. Such synthetic and supramolecular strategies enable us to construct photofunctional molecular architectures for light energy conversion, such as photovoltaics. In photovoltaic cells, processes such as light-harvesting, charge separation for carrier generation, and carrier transport are generally required. Therefore, the construction of
Ordered assemblies of protonated porphyrin in the form of J- and H-type aggregates have been achieved on the single-wall carbon nanotube (SWCNTs) surface. This unusual molecular aggregation phenomenon driven by SWCNTs further enables macroscopic assembly in the form of linear bundles.
Photochemical solar cells have been constructed from organized assemblies of single-walled carbon nanotubes (SWCNT) and protonated porphyrin on nanostructured SnO2 electrodes. The protonated form of porphyrin (H4P2+) and SWCNT composites form 0.5-3.0 microm-sized rodlike structures and they can be assembled onto nanostructured SnO2 films [optically transparent electrode OTE/SnO2] by an electrophoretic deposition method. These organized assemblies are photoactive and absorb strongly in the entire
Novel organic solar cells prepared using quaternary self-organization of porphyrin (donor) and fullerene (acceptor) dye units by clusterization with gold nanoparticles on SnO2 electrodes exhibit the remarkable enhancement of the photoelectrochemical properties relative to the reference systems.
Organic photovoltaic cells using supramolecular complexes of porphyrin−peptide oligomers (porphyrin-functionalized α-polypeptides) with fullerene demonstrate remarkable enhancement in the photoelectrochemical performance as well as broader photoresponse in the visible and near-infrared regions by increasing the number of porphyrin units in α-polypeptide structures. A high power conversion efficiency (η) of 1.3% and a maximum incident photon-to-photocurrent efficiency (IPCE) of 42% were attained
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 s
Organic photovoltaic cells made using supramolecular complexes of porphyrin dendrimers with fullerenes demonstrate remarkable enhancement in the photoelectrochemical performance as well as broader photoresponse in the visible and near‐infrared regions relative to the reference system. This demonstrates that molecular assemblies of C 60 and porphyrins with dendritic structures are effective in photoenergy conversion systems (see Figure).
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 de
Composite molecular nanoclusters of fullerene and porphyrin prepared in acetonitrile/toluene mixed solvent absorb light over the entire spectrum of visible light. Upon slow evaporation of the solvent on the copper grid, these mixed nanoclusters undergo close-packed stacking to produce either tubular- or square-shaped microcrystallites and differ from those obtained from single-component clusters. The highly colored composite clusters can be assembled as 3-dimensional arrays onto nanostructured S
Seeing the light: Stacked-cup carbon nanotubes (SCCNTs) have been electrophoretically deposited on conducting glass electrodes from a suspension in THF by using a dc field (see picture). These SCCNT films undergo charge separation and deliver photocurrent on irradiation with visible light. The photon conversion efficiency of 17 % observed with the SCCNT system is two orders of magnitude greater than those obtained with carbon nanotubes.
Photofunctional molecular architectures with well-defined shapes and sizes are of great interest because of various applications such as photovoltaics, photocatalysis, and electronics. Porphyrins are promising building blocks for organized nanoscale superstructures, which perform many of the essential light-harvesting and photoinduced electron/energy transfer reaction. In this Perspective, we present the recent advances in supramolecular architectures of porphyrins for solar energy conversion. F
Pentacene dimers bridged by a phenylene at ortho and meta positions [denoted as o-(Pc)<sub>2</sub> and m-(Pc)<sub>2</sub>] were synthesized to examine intramolecular orientation-dependent multiexciton dynamics, especially focusing on singlet fission (SF) and recombination from correlated triplet pairs [(TT)]. Absorption and electrochemical measurements indicated strong intramolecular couplings of o-(Pc)<sub>2</sub> relative to m-(Pc)<sub>2</sub>. Femtosecond and nanosecond TA measurements succes
A series of fluorescent "push-pull" tetrathia[9]helicenes based on quinoxaline (acceptor) fused with tetrathia[9]helicene (donor) derivatives was synthesized for control of the excited-state dynamics and circularly polarized luminescence (CPL) properties. In this work, introduction of a quinoxaline onto the tetrathia[9]helicene skeleton induced the "push-pull" character, which was enhanced by further introduction of an electron-releasing Me2 N group or an electron-withdrawing NC group onto the q
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