Eigh efficiency solar energy conversion by nano-structured InGaN semiconductor photoelectrode

2007 Fiscal Year Final Research Report Summary

• Project/Area Number: 16310085
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Nanomaterials/Nanobioscience
• Research Institution: The University of Electro-Communications
• Principal Investigator: KOBAYASHI Naoki The University of Electro-Communications, Faculty of Applied Physics and Chemistry, Professor (10361825)
• Project Period (FY): 2004 – 2007
• Keywords: water photolysis / energy resource of hydrogen / semiconductor photoelectrode / nitride semiconductors / gallium nitride / indium gallium nitride / solar energy

Research Abstract

Hydrogen was evolved at a zero bias when a p-type GaN cathode in an electrolyte solution is irradiated with UV light, although both hydrogen evolution rate and photocurrent decrease during irradiation. Spontaneous hydrogen evolution indicates that the conduction band-edge of p-GaN is above the reduction potential of H+(aq). From the relationship between the volume of generated hydrogen and the amount of electrons traveling from the Pt anode to the p-GaN cathode, the reaction efficiency of electrons injected from the conduction band of the p-GaN cathode with H+(aq) in a neutral Na2SO4 electrolyte solution is larger than 70%. As a result, the overall quantum efficiency for the hydrogen generation before degradation is estimated to be 4-6% at a wavelength of 340 nm by considering the incident photon-to-current efficiency of p-GaN. We also studied the electron transport between InGaN and electrolyte solution by using cyclic voltammetry, compared with Pt, Ti02/FTO (Fluorine-doped Tin Oxide glass). The forward and reverse reactions of H2→2H+ + 2e occurred at Pt and TiO2/FTO electrodes. In contrast, in GaN and In0.12Ga0.88N electrodes, only forward reaction occured and no reserve reaction of H2→2H+ + 2e was observed. These results show that GaN and In0.12Ga0.88N have higher comduction band-edge potentials than the reduction potential of H+ (aq) in water. Moreover, we observed cathodic photocurrent with p-In0.12Ga0.88N electrode under 405nm visible light irradiation in Na2SO4 solution and H2 bubbles on electrode surface were in-situ detected by monitoring the scattered light intensity.

Research Products

• [Journal Article] p-GaN cathode degradation correlated with hydrogen passivation during water photolysis under uv light (2007)
  • Author(s): 高木、鳴海、小林、山本、伴、若尾
  • Journal Title: Japanese Journal of Applied Physics 46 Pages: 572-573
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] Minority carrier diffusion lengths in MOVPE-grown-p-InGaN and perform ance of AlGaN/InGaN/GaN double heterojunction bipolar transistors (2007)
  • Author(s): 熊倉、牧本、小林、橋詰、福井、長谷川
  • Journal Title: Journal of Crystal Growth 298 Pages: 787-790
  • Description: 「研究成果報告書概要(和文)」より
  • Peer Reviewed
• [Journal Article] p-GaN cathode degradation correlated with hydrogen passivation during water photolysis under uv light (2007)
  • Author(s): D., Takagi, T., Narumi, N., Kobayashi, J., Yamamoto, Y., Ban, K., Wakao
  • Journal Title: Jpn. J. Appl. Phys Vol. 46 Pages: 572-573
  • Description: 「研究成果報告書概要(欧文)」より
• [Journal Article] Minority carrier diffusion lengths in MOVPE-grown-p-InGaN and performance of AlGaN/InGaN/GaN double heterojunction bipolar transistors (2007)
  • Author(s): K., Kumakura, T., Makimoto, N., Kobayashi, T., Hashizume, T., Fukui, H., Hasegawa
  • Journal Title: J. Cryst. Growth Vol. 298 Pages: 787-790
  • Description: 「研究成果報告書概要(欧文)」より
• [Presentation] Electron transport at InGaN/electrolyte interface and its application to water photolysis using visible light (2007)
  • Author(s): S., Usui, T., Narumi, J., Tokue, N., Kobayashi, J., Yamamoto, Y., Ban, K., Wakao
  • Organizer: the Int. Conf. on SSDM, Tsukuba
  • Year and Date: 20070000
  • Description: 「研究成果報告書概要(欧文)」より
• [Presentation] Electron transport at InGaN/electrolyte interface and its application to water photolysis using visible light (2007)
  • Author(s): 臼井、鳴海、徳江、小林、山本、伴、若尾
  • Organizer: the Int. Conf. on SSDM
  • Place of Presentation: つくば国際会議場
  • Year and Date: 2007-09-20
  • Description: 「研究成果報告書概要(和文)」より
• [Remarks] 「研究成果報告書概要(和文)」より
  • URL: http://cell.pc.uec.ac.jp/