title: Enhanced Photocurrent Generation from Bacteriorhodopsin Photocells Using Grating-Structured Transparent Conductive Oxide Electrodes.
abstract: We fabricated a grating-structured electrode made of indium-doped zinc oxide (IZO) with a high refractive index (approximately 2) for a bacteriorhodopsin (bR) photocell. We investigated the photocurrent characteristics of the bR photocell and demonstrated that the photocurrent values from the bR/IZO electrode with the grating structure with a grating period of 340 nm were more than 3.5-4 times larger than those without the grating structure. The photocurrent enhancement was attributed to the resonance effect due to light coupling to the grating structure as well as the scattering effect based on the experimental results and analysis using the photonic band structure determined using finite-difference time-domain (FDTD) simulations. The refractive index of the bR film in electrolyte solution (1.40) used in the FDTD simulations was estimated by analyzing the extinction peak wavelength of 20-nm gold colloids in the bR film. Our results indicate that the grating- or photonic-crystal-structured transparent conductive oxide (TCO) electrodes can increase the light use efficiency of various bR devices such as artificial photosynthetic devices, solar cells, and light-sensing devices.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kaji
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Kasai
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Haruyama
authors.forename: Toshiki
authors.initials: T
authors.lastname: Yamada
authors.forename: Shin-Ichiro
authors.initials: S
authors.lastname: Inoue
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Tominari
authors.forename: Rieko
authors.initials: R
authors.lastname: Ueda
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Terui
authors.forename: Shukichi
authors.initials: S
authors.lastname: Tanaka
authors.forename: Akira
authors.initials: A
authors.lastname: Otomo
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000528:radiation effects; D001674:Bioelectric Energy Sources; D003217:Conductometry / Q000295:instrumentation*; D004566:Electrodes; D004735:Energy Transfer; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007909:Lenses; D008027:Light; D010087:Oxides / Q000737:chemistry; D010783:Photometry / Q000295:instrumentation*; D012031:Refractometry / Q000295:instrumentation*
chemical_list: D010087:Oxides; D001436:Bacteriorhodopsins