• Advances in nano research
• /
• 제1권1호
• /
• pp.43-58
• /
• 2013

Zinc oxide (ZnO) is a unique semiconductor material that exhibits numerous useful properties for dye-sensitized solar cells (DSSCs) and other applications. Various thin-film growth techniques have been used to produce nanowires, nanorods, nanotubes, nanotips, nanosheets, nanobelts and terapods of ZnO. These unique nanostructures unambiguously demonstrate that ZnO probably has the richest family of nanostructures among all materials, both in structures and in properties. The nanostructures could have novel applications in solar cells, optoelectronics, sensors, transducers and biomedical sciences. This article reviews the various nanostructures of ZnO grown by various techniques and their application in DSSCs. The application of ZnO nanowires, nanorods in DSSCs became outstanding, providing a direct pathway to the anode for photo-generated electrons thereby suppressing carrier recombination. This is a novel characteristic which increases the efficiency of ZnO based dye-sensitized solar cells.

• 한국재료학회지
• /
• 제28권4호
• /
• 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.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
• /
• pp.84-84
• /
• 2008

A multidimensional ZnO light-emitting diode LEDstructure comprising film/nanorods/substrate was fabricated on a p-type Si substrate using metal organic chemical vapor deposition at relatively low growth temperature. The filmlike top layer used for the metal contact was continuously formed on the ZnO nanorods by varying the growth conditions and the resulting structure allowed us to utilize the nanorods with intense emission as an active layer. We investigated the performance of the resulting multidimensional LED. An extremely high breakdown voltage and low reverse leakage current as well as typical rectification behavior were observed in the I-V characteristics.

• 한국진공학회지
• /
• 제18권1호
• /
• pp.73-78
• /
• 2009

본 연구에서는 metal oxide chemical vapor deposition (MOCVD)을 이용하여 p형 실리콘(100) 기판 위에 30 nm 두께의 산화 아연 완충층을 $500^{\circ}C$ 에서 증착 시킨 후, 그 위에 산화 아연 나노로드를 수열합성법을 이용하여 성장시켰다. 그리고 산화아연 나노로드 성장 시 0.02몰${\sim}$0.5몰의 다양한 농도의 전구체를 사용함으로써 그에 따라 변화되는 산화 아연 나노로드의 배열상태, 구조적, 그리고 광학적 특성 평가를 실시하였다. 특성 평가는 FE-SEM(field emission scanning electron microscopy), XRD(X-ray diffraction), 그리고 PL(photoluminescence) 등의 분석 방법들을 통해 이루어졌다 본 연구를 통하여 전구체의 농도가 증가할수록 나노로드의 직경과 길이가 길어지며 0.3몰의 농도에서 뛰어난 광학 특성이 나타나는 것을 발견할 수 있었다.

• Journal of Ceramic Processing Research
• /
• 제19권5호
• /
• pp.401-406
• /
• 2018

We investigated the effect of ZnO seed layer thickness on the density of ZnO nanorod arrays. ZnO has been deposited using two distinct processes consisting of the seed layer deposition using ALD and subsequent hydrothermal ZnO growth. Due to the coexistence of the growth and dissociation during ZnO hydrothermal growth process on the seed layer, the thickness of seed layer plays a critical role in determining the nanorod growth and morphology. The optimized thickness resulted in the regular ZnO nanorod growth. Moreover, the introduction of ALD to form the seed layer facilitates the growth of the nanorods on ultrathin seed layer and enables the densification of nanorods with a narrow change in the seed layer thickness. This study demonstrates that ALD technique can produce densely packed, virtually defect-free, and highly uniform seed layers and two distinctive processes may form ZnO as the final product via the initial nucleation step consisting of the reaction between $Zn^{2+}$ ions from respective zinc precursors and $OH^-$ ions from $H_2O$.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2006년도 제31회 학술논문발표회 초록집
• /
• pp.57-57
• /
• 2006

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
• /
• pp.204.1-204.1
• /
• 2013

Fluorine, the radius of which is close to that of oxygen, could be an appropriate anion doping candidate. A lower lattice distortion could be expected for F doping, compared with Al, Ga, and In doping. F-doped ZnO (FZO) and undoped ZnO nanorods were grown onto glass substrate by the hydrothemal method. The doping level in the solution, designated by F/Zn atomic ratio of was varied from 0.0 to 10.0 in 2.0 steps. To investigate the effects of the structure and optical properties of FZO nanorods were investigated using X-ray diffraction, UV-visible spectroscopy and photoluminescence (PL). For the PL spectra, the maximum peak position of NBE moves to higher energy, from 0 to 4 at.%. As the doping concentration increases, the maximum peak position of NBE gradually moves to lover energy, from 4 to 10 at.%.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 추계학술대회 논문집
• /
• pp.243-243
• /
• 2009

Bi2O3 doped ZnO nanostructures structure were successfully synthesized by a thermal evaporatiion process and their structural characteristics were investigated. It is demonstrated that the growth condition such as the areal density, pretreatment of the substrates and growth temperature have great influence on the morphology and the alignment of the nanorods arrays. The density of Bi2O3 doped ZnO nanostructures is controlled by the gold (Au) nanoparticle density deposited on the silicon substrates. Relatively homogenous size and shape were observed by introducing gold(Au) seed-layer as nucleation centers on the substrates prior to the VLS reaction. The samples were characterized by X-ray diffraction, scanning electron microscopy.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
• /
• pp.118.2-118.2
• /
• 2011

In order to increase the energy conversion efficiency of dye-sensitized solar cells (DSSCs), we employed a counter electrode that was platinum coated using a doctor blade technique on synthesized ZnO nanostructures on fluorinedoped tin oxide (FTO). The ZnO nanostructures possessing high electrochemical activity and large surface area of the counter electrode were grown by a chemical bath deposition (CBD) method at various times, 2, 4, and 8 h. The efficiency of DSSC with the Pt-ZnO counter electrode was improved 7.01% (grown for 2 h), 7.63% (grown for 4 h), and 6.13% (grown for 8 h), respectively. Compared with a standard DSSC without ZnO nanostructures, whose efficiency was 6.27%, the energy conversion efficiency increased approximately 22% for the DSSC with the Pt-ZnO (grown for 4 h) electrode. It indicates that the Pt coated on the ZnO nanostructure improves the electrocatalytic activity of the counter electrode.

• 한국수소및신에너지학회논문집
• /
• 제24권2호
• /
• pp.107-112
• /
• 2013

The ZnO is able to produce hydrogen from water however it can only absorb ultraviolet region due to its 3.37eV of wide band gap. Therefore efficiency of solar hydrogen production is low. In this work we report investigation results of improved visible light photo-catalytic properties of CdSe quantum dots(QDs) sensitized ZnO nanorod heterostructures. Hydrothermally vertically grown ZnO nanorod arrays on FTO glass were sensitized with CdSe by using SILAR(successive ionic layer adsorption and reaction) method. Morphology of grown ZnO and CdSe sensitized ZnO nanorods had been investigated by FE-SEM that shows length of $2.0{\mu}m$, diameter of 120~150nm nanorod respectively. Photocatalytic measurements revealed that heterostructured samples show improved photocurrent density under the visible light illumination. Improved visible light performance of the heterostructures is resulting from narrow band gap of the CdSe and its favorable conduction band positions relative to potentials of ZnO band and water redox reaction.