• Journal of the Korean institute of surface engineering
• /
• v.40 no.4
• /
• pp.190-196
• /
• 2007

Dye sensitized solar cells(DSSC) are the most promising future energy resource due to their high energy efficiency, low production cost, and simple manufacturing process. But one problem in DSSC is short life time compared to silicon solar cells. This problem occurred from photocatalytic degradation of dye material by nanometer sized $TiO_2$ particles. To prevent dye degradation as well as to increase its life time, the transparent coating film is needed for UV blocking. In this study, we synthesized nanometer sized $TiO_2$ particles in sols by increasing its internal pressure up to 200 bar in autoclave at $120^{\circ}C$ for 10 hrs. The synthesized $TiO_2$ sols were all formed with brookite phase and their particle size was several nm to 30 nm. Synthesized $TiO_2$ sols were coated on the backside of fluorine doped tin oxide(FTO) glass by ink jet printing method. With increasing coating thickness by repeated ink jet coating, the absorbance of UV region (under 400 nm) also increases reasonably. Decomposition test of titania powders dispersed in 0.1 mM amaranth solution covered with $TiO_2$ coating glass shows more stable dye properties under UV irradiation, compared to that with as-received FTO glass.

• Journal of Adhesion and Interface
• /
• v.23 no.2
• /
• pp.39-43
• /
• 2022

In optoelectronic devices including displays and solar cells that convert electricity into light or light into electricity, it is important to control optical behavior of light to improve device efficiency. Specifically, the control of internal emitting light in the OLEDs can induce more light to go out, improving luminous efficiency. In addition, the control of optical behavior of incident light in solar cells can increase optical path in the light absorption layer, increasing power-conversion efficiency. In this study, we generated wrinkles as a physical structure to control optical behavior of light and independently controlled their wavelength and height by changing stress relaxation time. To explore the effect of wavelength and height on optical behavior, we conducted UV/Vis spectroscopy analysis of wrinkles with various heights at a constant wavelength or various wavelengths at a comparable height, figuring out a wrinkle with high aspect ratio has more dispersive light and less straight light. It indicates that high aspect ratio is required to change the optical behavior and increase the optical path.

• Journal of the Korean Ceramic Society
• /
• v.53 no.1
• /
• pp.105-109
• /
• 2016

We prepared a working electrode (WE) with a blocking layer (BL) containing 0 ~ 0.5 wt% Ag nano powders to improve the energy conversion efficiency (ECE) of dye sensitized solar cell (DSSC). FESEM and micro-Raman were used to characterize the microstructure and phase. UV-VIS-NIR spectroscopy was employed to determine the adsorption of the WE with Ag nano powders. A solar simulator and a potentiostat were used to confirm the photovoltaic properties of the DSSC with Ag nano powders. From the results of the microstructural analysis, we confirmed that Ag nano powders with particle size of less than 150 nm were dispersed uniformly on the BL. Based on the phase and adsorption analysis, we identified the existence of Ag and found that the adsorption increased when the amount of Ag increased. The photovoltaic results show that the ECE became 4.80% with 0.3 wt%-Ag addition compared to 4.31% without Ag addition. This improvement was due to the increase of the localized surface plasmon resonance (LSPR) of the BL resulting from the addition of Ag. Our results imply that we might be able to improve the efficiency of a DSSC by proper addition of Ag nano powder to the BL.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.387.1-387.1
• /
• 2016

Transparent materials are necessary for most photoelectric devices, which allow the light generation from electric energy or vice versa. Metal oxides are usual materials for transparent conductors to have high optical transmittance with good electrical properties. Functional designs may apply in various applications, including solar cells, photodetectors, and transparent heaters. Nanoscale structures are effective to drive the incident light into light-absorbing semiconductor layer to improve solar cell performances. Recently, the new metal oxide materials have inaugurated functional device applications. Nickel oxide (NiO) is the strong p-type metal oxide and has been applied for all transparent metal oxide photodetector by combining with n-type ZnO. The abrupt p-NiO/n-ZnO heterojunction device has a high transmittance of 90% for visible light but absorbs almost entire UV wavelength light to show the record fastest photoresponse time of 24 ms. For other applications, NiO has been applied for solar cells and transparent heaters to induce the enhanced performances due to its optical and electrical benefits. We discuss the high possibility of metal oxides for current and future transparent electronic applications.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.10
• /
• pp.2883-2888
• /
• 2013

To enhance the power conversion efficiency of dye-sensitized solar cell (DSSC), the surface of titanium dioxide ($TiO_2$) photoelectrode was modified by hydroxylation treatment with $NH_4OH$ solution at $70^{\circ}C$ for 6 h. The $NH_4OH$ solutions of various concentrations were used to introduce the hydroxyl groups on $TiO_2$ surface. As the concentration of $NH_4OH$ was increased, the short-circuit current density ($J_{SC}$) value and conversion efficiency of solar cells were increased because the amount of adsorbed dye molecules on $TiO_2$ surface was increased. As a result of the surface modification to introduce hydroxyl groups, the concentration of adsorbed dye on the $TiO_2$ surface could be improved up to 32.61% without the changes of morphology, surface area and pore volume of particles. The morphology, the specific surface area, the pore volume and the chemical states of $TiO_2$ surface were characterized by using FE-SEM, $N_2$ adsorption-desorption isotherms and XPS measurements. The amount of adsorbed dye and the performance of fabricated cells were analyzed by using UV-Vis absorption spectroscopy and solar simulator.

• Journal of the Korean Ceramic Society
• /
• v.52 no.5
• /
• pp.380-383
• /
• 2015

We prepared the $TiO_2$ layer with 0 ~ 4 wt% of polystyrene (PS) beads having a radius of 250 nm to increase the dye adsorption and energy conversion efficiency (ECE) of a dye sensitized solar cell (DSSC). Then, we fabricated DSSCs using $0.45cm^2$ active area. FE-SEM was used to characterize the microstructure consisting of $TiO_2$ layer and PS beads. UV-VIS-NIR was used to determine the optical absorbance of working electrodes (WEs). Solar simulator and potentiostat were used to determine the photovoltaic properties. We observed that pores having a radius of 250 nm were formed with the density of $0.15ea/{\mu}m^2$ in $TiO_2$ layers after conducting the sintering process. The absorbance in visible light regime was found to increase with the increase in the amount of PS beads. The ECE increased from 4.66% to 5.25% when the amount of PS beads was increased from 0 to 4 wt%. This is because the pores of PS beads increased the adsorption of dye. Our results indicate that the ECE of the DSSCs can be enhanced by the addition of an appropriate amount of PS beads into $TiO_2$ layers.

• Journal of the Korean Ceramic Society
• /
• v.52 no.5
• /
• pp.384-388
• /
• 2015

We prepared blocking layers by adding 0.0 ~ 0.6 wt% nano diamond blends (DBs) to $TiO_2$ blocking layers to improve the energy conversion efficiencies (ECEs) of dye sensitized solar cells (DSSCs). TEM and micro-Raman spectroscopy were used to characterize the microstructure and phases of DBs, respectively. Optical microscopy and FE-SEM were used to analyze the microstructure of the $TiO_2$ blocking layer with DBs. UV-VIS-NIR spectroscopy was used to determine the absorbance of the working electrodes. A solar simulator and a potentiostat were used to determine the photovoltaic properties and the impedance of the DSSCs with DBs. From the results of the DBs analysis, we determined a 6.97 nm combination of nano diamonds and graphite. We confirmed that ECE increased from 5.64 to 6.48 % when the added DBs increased from 0.0 to 0.2 wt%. This indicates that the effective surface area and electron mobility increased when DBs were added to the $TiO_2$ blocking layer. Our results indicate that the ECE of DSSCs can be enhanced by adding an appropriate amount of DBs to the $TiO_2$ blocking layers.

• Journal of Environmental Science International
• /
• v.30 no.1
• /
• pp.57-67
• /
• 2021

Photocatalytic green energy H2 production utilizing inexhaustible solar energy has been considered as a potential solution to problems of energy scarcity and environmental contamination. However, the design of a cost-effective photocatalyst using simple synthesis methodology is still a grand challenge. Herein, a low-cost transition metal, Cu-loaded one-dimensional TiO2 nanorods (Cu/TNR) were fabricated using an easy-to-use synthesis methodology for significant H2 production under simulated solar light. X-ray photoelectron spectral studies and electron microscopy measurements provide evidence to support the successful formation of the Cu/TNR catalyst under our experimental conditions. UV-vis DRS studies further demonstrate that introducing Cu on the surface of TNR substantially increases light absorption in the visible range. Notably, the Cu/TNR catalyst with optimum Cu content, achieved a remarkable H2 production with a yield of 39,239 µmol/g after 3 h of solar light illumination, representing 7.4- and 27.7-fold enhancements against TNR and commercial P25, respectively. The notably improved H2 evolution activity of the target Cu/TNR catalyst was primarily attributed to its excellent separation and efficiently hampered recombination of photoexcited electron-hole pairs. The Cu/TNR catalyst is, therefore, a potential candidate for photocatalytic green energy applications.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.158-158
• /
• 2011

$Cu(In_xGa_{1-x})Se_2$ (CIGS) thin film solar cell is one of the most promising solar cells in photovoltaic devices. CIGS has a direct band gap which varied from 1.0 to 1.26 eV, depending on the Ga to In ratio. Also, CIGS has been studying for an absorber in thin film solar cells due to their highest absorption coefficient which is $1{\times}10^5cm^{-1}$ and good stability for deposition process at high temperature of $450{\sim}590^{\circ}C$. Currently, the highest efficiency of CIGS thin film solar cell is approximately 20.3%, which is closely approaching to the efficiency of poly-silicon solar cell. The deposition technique is one of the most important points in preparing CIGS thin film solar cells. Among the various deposition techniques, the sputtering is known to be very effective and feasible process for mass production. In this study, CIGS thin films have been prepared by rf magnetron sputtering method using a single target. The optical and structural properties of CIGS films are generally dependent on deposition parameters. Therefore, we will explore the influence of deposition power on the properties of CIGS films and the films will be deposited by rf magnetron sputtering using CIGS single target on Mo coated soda lime glass at $500^{\circ}C$. The thickness of CIGS films will be measured by Tencor-P1 profiler. The optical properties will be measured by UV-visible spectroscopy. The crystal structure will be analyzed using X-ray diffraction (XRD). Finally the optimal deposition conditions for CIGS thin films will be developed.

• Journal of Photoscience
• /
• v.9 no.2
• /
• pp.186-189
• /
• 2002

Many of the adverse effects of solar UV exposure appear to be directly attributable to damage to epidermal DNA. In particular, cyclobutane pyrimidine dimers (CPD) may initiate mutagenic changes as well as induce signal transduction responses that lead to a loss of skin immune surveillance and micro-destruction of skin structure. Our approach is to reverse the DNA damage using prokaryotic DNA repair enzymes delivered into skin using specially engineered liposomes. T4 endonuclease V encapsulated in liposomes (T4N5 liposome lotion) enhanced DNA repair by shifting repair of CPD from the nucleotide excision to the base excision repair pathway. Following topical application to humans, increased repair limited UV-induction of cytokines, many of which are immunosuppressive. In a recent clinical study, topical treatment of UV-irradiated human skin with T4N5 liposome lotion reduced the suppression of the nickel sulfate contact hypersensitivity response. Similarly, the photoreactivating enzyme enhances repair by directly reversing CPDs after absorbing activating light. Here also treatment of UV-irradiated human skin with photoreactivating enzyme in liposomes and photoreactivating light restored the response to the contact allergen nickel sulfate. These findings confirm in humans the observation in mice that UV induced suppression of contact hypersensitivity is caused in part by CPDs. We have tested the ability of T4N5 liposome lotion to prevent UV-induced skin cancer in patients with xeroderma pigmentosum (XP), who have an elevated incidence of skin cancer resulting from a genetic defect in DNA repair. Daily use of the lotion for one year in a group of 20 XP patients reduced the average number of actinic keratoses by 68% and basal cell cancers by 30% compared to 9 patients in the placebo control group. Delivery of DNA repair enzymes to skin is a promising new approach to photoprotection.