• Journal of the Korean Ceramic Society
• /
• v.20 no.4
• /
• pp.356-360
• /
• 1983

The photocurrent vs. potential characteristics of the $TiO_2$ ceramic electrodes have been investigated as functions of numerous variables including sample purity hydrogen reduction condition and pH of the electrolyte. The difference inphotoresponse between 99.99% and 98.5% $TiO_2$ electrodes was due to electron trapping effect. As the hydrogen reducing temperature of $TiO_2$ electrodes were increased the photocurrent was also increased to certain condition and then decreased. These results can be explained by the behavior of oxygen vacancies.

• Korean Journal of Materials Research
• /
• v.30 no.9
• /
• pp.441-446
• /
• 2020

Synthesizing nanostructured thin films of oxide semiconductors is a promising approach to fabricate highly efficient photoelectrodes for hydrogen production via photoelectrochemical (PEC) water splitting. In this work, we investigate the feasibility as an efficient photoanode for PEC water oxidation of zinc oxide (ZnO) nanostructured thin films synthesized via a simple method combined with sputtering Zn metallic films on a fluorine-doped tin oxide (FTO) coated glass substrate and subsequent thermal oxidation of the sputtered Zn metallic films in dry air. Characterization of the structural, optical, and PEC properties of the ZnO nanostructured thin film synthesized at varying Zn sputtering powers reveals that we can obtain an optimum ZnO nanostructured thin film as PEC photoanode at a sputtering power of 40 W. The photocurrent density and optimal photocurrent conversion efficiency for the optimum ZnO nanostructured thin film photoanode are found to be 0.1 mA/㎠ and 0.51 %, respectively, at a potential of 0.72 V vs. RHE. Our results illustrate that the ZnO nanostructured thin film has promising potential as an efficient photoanode for PEC water splitting.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.116-116
• /
• 2009

$TiO_2$ pastes was synthesized to obtained of high efficiency dye-sensitized solar cells using size dependent co-polymer. SBM co-polymer binder is consist of styrene, n-butyl acrylate, and methacrylic acid (SBM) monodisperse co-polymer binder materials and this $TiO_2$ pastes were applied of dye-sensitized solar cells (DSSCs). The photoanodes were characterized by ATR-Fourier Transform spectrometer, X-ray diffraction (XRD) and morphology was investigated by field emission scanning electron microscopy (FE-SEM). The photoelectrochemical properties of the thin films and the performance of DSSCs were measured by photovoltaic-current density, AC impedance and monochromatic incident photon-to-current conversion efficiency (IPCE). DSSC based on the 100nm size co-polymer binder was obtained conversion efficiency of 8.1% under irradiation of AM 1.5(100 $mWcm^2$).

• Korean Journal of Materials Research
• /
• v.26 no.11
• /
• pp.604-610
• /
• 2016

We report on the fabrication and characterization of a novel $Cu_2O/CuO$ heterojunction structure with CuO nanorods embedded in $Cu_2O$ thin film as an efficient photocathode for photoelectrochemical (PEC) solar water splitting. A CuO nanorod array was first prepared on an indium-tin-oxide-coated glass substrate via a seed-mediated hydrothermal synthesis method; then, a $Cu_2O$ thin film was electrodeposited onto the CuO nanorod array to form an oxide semiconductor heterostructure. The crystalline phases and morphologies of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy, as well as Raman scattering. The PEC properties of the fabricated $Cu_2O/CuO$ heterojunction photocathode were evaluated by photocurrent conversion efficiency measurements under white light illumination. From the observed PEC current density versus voltage (J-V) behavior, the $Cu_2O/CuO$ photocathode was found to exhibit negligible dark current and high photocurrent density, e.g. $-1.05mA/cm^2$ at -0.6 V vs. $Hg/HgCl_2$ in $1mM\;Na_2SO_4$ electrolyte, revealing the effective operation of the oxide heterostructure. The photocurrent conversion efficiency of the $Cu_2O/CuO$ photocathode was estimated to be 1.27% at -0.6 V vs. $Hg/HgCl_2$. Moreover, the PEC current density versus time (J-T) profile measured at -0.5 V vs. $Hg/HgCl_2$ on the $Cu_2O/CuO$ photocathode indicated a 3-fold increase in the photocurrent density compared to that of a simple $Cu_2O$ thin film photocathode. The improved PEC performance was attributed to a certain synergistic effect of the bilayer heterostructure on the light absorption and electron-hole recombination processes.

• Bulletin of the Korean Chemical Society
• /
• v.28 no.6
• /
• pp.953-958
• /
• 2007

Anchoring quantum dots (QDs) onto thermodynamically stable, large band gap oxide semiconductors is a very important strategy to enhance their quantum yields for solar energy conversion in both visible and near-IR regions. We describe a general procedure for anchoring a few chalcogenide QDs onto the titanium oxide layer. To anchor the colloidal QDs onto a mesoporous TiO2 layer, linker molecules containing both carboxylate and thiol functional groups were initially attached to TiO2 layers and subsequently used to capture dispersed QDs with the thiol group. Employing the procedure, we exploited cadmium selenide (CdSe) and cadmium telluride (CdTe) quantum dots (QDs) as inorganic sensitizers for a large band gap TiO2 layer of dye-sensitized solar cells (DSSCs). Their attachment was confirmed by naked eyes, absorption spectra, and photovoltaic effects. A few QD-TiO2 systems thus obtained have been characterized for photoelectrochemical solar energy conversion.

• Korean Journal of Materials Research
• /
• v.28 no.4
• /
• pp.214-220
• /
• 2018

We report on the fabrication and photoelectrochemical(PEC) properties of a $Cu_2O$ thin film/ZnO nanorod array oxide p-n heterojunction structure with ZnO nanorods embedded in $Cu_2O$ thin film as an efficient photoelectrode for solar-driven water splitting. A vertically oriented n-type ZnO nanorod array was first prepared on an indium-tin-oxide-coated glass substrate via a seed-mediated hydrothermal synthesis method and then a p-type $Cu_2O$ thin film was directly electrodeposited onto the vertically oriented ZnO nanorods array to form an oxide semiconductor heterostructure. The crystalline phases and morphologies of the heterojunction materials were characterized using X-ray diffraction and scanning electron microscopy as well as Raman scattering. The PEC properties of the fabricated $Cu_2O/ZnO$ p-n heterojunction photoelectrode were evaluated by photocurrent conversion efficiency measurements under white light illumination. From the observed PEC current density versus voltage (J-V) behavior, the $Cu_2O/ZnO$ photoelectrode was found to exhibit a negligible dark current and high photocurrent density, e.g., $0.77mA/cm^2$ at 0.5 V vs $Hg/HgCl_2$ in a $1mM\;Na_2SO_4$ electrolyte, revealing an effective operation of the oxide heterostructure. In particular, a significant PEC performance was observed even at an applied bias of 0 V vs $Hg/HgCl_2$, which made the device self-powered. The observed PEC performance was attributed to some synergistic effect of the p-n bilayer heterostructure on the formation of a built-in potential, including the light absorption and separation processes of photoinduced charge carriers.

• Transactions of the Korean hydrogen and new energy society
• /
• v.34 no.5
• /
• pp.413-420
• /
• 2023

Holmium-doped TiO₂ nanotubes (Ho-TNTs) were manufactured through anodization treatment and electrochemical deposition, and optimization experiments were conducted using various Holmium doping concentrations and time as variables. Surface as well as electrochemical characteristics were analyzed to study the prepared photocatalysts. Ho-TNTs were found to exist only in anatase phase through X-ray diffraction analysis. Ho-TNTs with 0.01 wt% 100 seconds shows a photocurrent density of 3.788 mA/cm² and an effective photo-conversion efficiency (PCE) of 4.30%, which is more efficient than pure TiO₂ nanotubes (pure-TNTs) (at bias potential 1.5 V vs. Hg/HgO). The photocatalytic activity of the aforementioned Ho-TNTs for hydrogen production was evaluated with the result of -29.20 µmol/h·cm².

• 한국신재생에너지학회:학술대회논문집
• /
• 2010.11a
• /
• pp.60.1-60.1
• /
• 2010

Chemically functionalized plant oils such as acrylated epoxidized soybean oil (AESO) and maleinized acrylated epoxidized soybean oil (MAESO) were used as new bio-based binders for $TiO_2$ electrodes of dye-sensitized solar cells (DSSC). More porous networks and larger porosities were fabricated on the $TiO_2$ films using plant oil binders due to the larger number of functionalities, in comparison with the film using polyethylene glycol (PEG). The charge-transfer resistance in the $TiO_2$ films was considerably shrunk due to the reduced impurity states. The short circuit photocurrent (Isc) and the open circuit photovoltage (Voc) of the cell using plant oil binders increased and the conversion efficiency improved significantly.

• Analytical Science and Technology
• /
• v.9 no.1
• /
• pp.62-71
• /
• 1996

The enhancement of the solar energy conversion efficiency into the electrical energy by the dye sensitization with a photoelectrochemical cell was studied. The magnitude of the rose bengal sensitized photocurrent containing the supersensitizer, thiourea was five times greater than that in the absence of thiourea. It was observed, however, that the long time span of irradiation causes the decrease in the photocurrent. Spectroscopic analysis of the dye solution showed that the dye molecule was photobleached and the insoluble aggregate which settles down in the solution, was formed as a result of the possible photocatalytic reaction and the disappearance of dye from the solution was the cause of the decreased photocurrent in the sensitization run.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.10a
• /
• pp.13.1-13.1
• /
• 2011

Photoelectrochemical solar cells such as dye-sensitized cells (DSSCs), which exhibit high performance and are cost-effective, provide an alternative to conventional p-n junction photovoltaic devices. However, the efficiency of such cells plateaus at 11~12%, in contrast to their theoretical value of 33%. The majority of research has focused on improving energy conversion efficiency of DSSC by controlling nanostructure and exploiting new materials in photoelectrode consisting of semiconducting oxide nanoparticles and a transparent conducting oxide electrode (TCO) [1-5]. In this presentation, we introduce inverse opal-based scattering layers containing highly crystalline anatase nanoparticles and their feasibility for use as bi-functional light scattering layer is discussed in terms of optical reflectance and charge generation properties as a function of optical wavelength. A new ITO nanowire-based photoelecrode is also introduced and its unique charge collection property is presented, demonstrating potential use for highly efficient charge collection in DSSC.