In photosynthesis, two photosystems are exquisitely located for uphill electron transport with redox species to bridge these photosystems and this is called Z-scheme type structure. This smart photoenergy conversion system must be modeled in highlyefficient artificial photoenergy conversion. Our strategy here is to cooperate a couple of photoactive electrodes for mimicking a Z-scheme type structure using two different photoelectrodes and bridging redox couple. An early study implied the possibility of a tandem-type photoelectric conversion system, though the cell performance had been considerably low. 1 Later, Bach's group also proposed a similar structure consisting of nand p-type dye-sensitized solar cell (DSC) electrodes and achieved high conversion efficiency. Recently, we reported a simple fabrication method of photoactive polymer electrode consisting of 5,10,15,20-tetra(3-thienyl)-21H,23H-porphyrin (TThP) and 2,2¢-bithiophene (BiTh) by electropolymerization (Scheme 1a). 6-9 As the photoactive electrode for a solar cell, it could generate 32% of photon-to-electron conversion efficiency under the monochromatic light. Since this polymer electrode functions as a photocathode and has a good affinity with the I -/I 3 -redox couple, it is very fascinating to use in a Z-scheme type photoelectrochemical cell with a smart choice of a good compatible photoanode. In this paper, we found that the combination of the above-described polymer electrode and the electrode for DSC successfully acted as a Z-scheme type photoelectrochemical cell with higher photovoltage TThP was synthesized by condensation of pyrrole (Aldrich) and 3-thiophenecarboxyaldehyde (Aldrich) according to the previous procedures. 6 TThP was identified by 1 H-NMR, absorption spectroscopy, matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) and elemental analysis; impurities in the TThP were found to be negligible. (TThP+polythiophene (pTh)) thin films were fabricated on the surface of an indium-tin-oxide (ITO) glass by electrochemical polymerization of TThP and BiTh (Wako pure chemicals) in a similar manner as before. 6 The ITO glass (Sanyo Vacuum Industries, 2 ¥ 2 ¥ 0.3 cm), cleaned ultrasonically in 2-propanol and then dichloromethane, was used as a working electrode. A platinum wire and a silver wire were used as the counter and reference electrodes, respectively. A dichloromethane solution This journal i
