• Journal of Electrochemical Science and Technology
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• v.13 no.4
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• pp.453-461
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• 2022

A chemically sintered and binder-free paste of TiO₂ nanoparticles (NPs) was prepared using a binary-liquid mixture of 1-octanol and CCl₄. The 1:1 (v/v) complex of CCl₄ and 1-octanol easily interacted chemically with the TiO₂ NPs and induced the formation of a highly viscous paste. The as-prepared binary-liquid paste (P_BL)-based TiO₂ film exhibited the complete removal of the binary-liquid and residuals with the subsequent low-temperature sintering (~150℃) and UV-O₃ treatment. This facilitated the fabrication of TiO₂ photoanodes for flexible dye-sensitized solar cells (f-DSSCs). For comparison purposes, pure 1-octanol-based TiO₂ paste (P_O) with moderate viscosity was prepared. The P_BL-based TiO₂ film exhibited strong adhesion and high mechanical stability with the conducting oxide coated glass and plastic substrates compared to the P_O-based film. The corresponding low-temperature sintered P_BL-based f-DSSC showed a power conversion efficiency (PCE) of 3.5%, while it was 2.0% for P_O-based f-DSSC. The P_BL-based low- and high-temperature (500℃) sintered glass-based rigid DSSCs exhibited the PCE of 6.0 and 6.3%, respectively, while this value was 7.1% for a 500℃ sintered rigid DSSC based on a commercial (or conventional) paste.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.355-356
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• 2013

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.346.1-346.1
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• 2014

Porous nano crystalline $TiO_2$ is currently used as a working electrode in a dye-sensitized solar cell (DSSC). The conventional working electrode is comprised of absorption layer (particle size:~20 nm) and scattering layer (particle size:~300 nm). We inserted window layer with 10 nm particle size in order to increase transmittance and specific surface area of $TiO_2$. The electrochemical impedance spectroscope analysis was conducted to analysis characterization of the electronic behavior. The Bode phase plot and Nyquist plot were interpreted to confirm the internal resistance caused by the insertion of window layer and carrier lifetime. The photocurrent that occurred in working electrode, which is caused by rise in specific surface area, increased. Accordingly, it was found that insertion of window layer in the working electrode lead to not only effectively transmitting the light, but also increasing of specific surface area. Therefore, it was concluded that insertion of window layer contributes to high conversion efficiency of DSSCs.

• Transactions on Electrical and Electronic Materials
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• v.16 no.6
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• pp.303-307
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• 2015

Multilayered films of ITO (In₂O₃:SnO₂ = 9:1)/SiO₂ were deposited on soda-lime glass by RF/DC magnetron sputtering at 500℃ to improve the energy conversion efficiency of dye-sensitized solar cells (DSSCs). The light absorption of the dye was improved by decrease in light reflectance from the surface of the DSSCs by using an ITO film. In order to estimate the optical characteristics and compare them with experimental results, a simulation program named EMP (essential macleod program) was used. EMP results revealed that the multilayered thin films showed high transmittance (approximate average transmittance of 79%) by adjusting the SiO₂ layer thickness. XRD results revealed that the ITO and TiO₂ films exhibited a crystalline phase with (400) and (101) preferred orientations at 2 θ = 26.24° and 35.18°, respectively. The photocurrent-voltage (I-V) characteristics of the DSSCs were measured under AM 1.5 and 100 mW/cm² (1 sun) by using a solar simulator. The DSSC fabricated on the ITO film with a 0.1-nm-thick SiO₂ film showed a Voc of 0.697 V, J_sc of 10.596 mA/cm² , FF of 66.423, and calculated power conversion efficiency (η_AM1.5) of 5.259%, which was the maximum value observed in this study.

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

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.338-343
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• 2015

Dye sensitized solar cells (DSSCs), which is one of the contending renewable energy sources, have the problem of low efficiency. To improve the efficiency, the fast electron transport and long electron lifetime are required. In this study, one-dimensional sodium hexatitanate, which is expected to have an advantageous structure for electron transports, was synthesized and the feasibility of the material on DSSC was tested. Its physical properties were characterized by the SEM, XRD, and BET method. The dye adsorption and solar cell properties were also characterized. In addition to the expectation of fast electron transport, sodium hexatitanate showed longer electron lifetime: This means sodium hexatitanate can improve the DSSC efficiency. However, it showed low current and voltage because of the low surface area leading to the low amount of dye adsorbed. Therefore, it should be mixed with titanium oxide with high surface area for the optimal performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.5
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• pp.380-384
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• 2013

In this paper, we have developed a low temperature process to make two type of paste by using $TiO_2$ nanoparticles(P25). The interconnections between substrate and $TiO_2$ films or link between particles of free-binder paste(FP1, FP2, FP3) is very poor. Therefore, the Titanium(IV) isopropoxide was added to the TP paste to improve the interconnection. Electron transport time (${\tau}_t$) and recombination time (${\tau}_r$) are analyzed by IMPS (intensity-modulated photocurrent spectroscopy) and IMVS(Intensity-modulated photovoltage spectroscopy). In the results, ${\tau}_t$ of TP paste based DSSCs (about $4.3{\times}10^{-3}$) is faster than other samples. ${\tau}_r$ is longer from $2.7{\times}10^{-2}$ s of FP2 to $3.0{\times}10^{-2}$ s of TP. A solar conversion efficiency (DSSCs) of TP is 3.54% for an incident solar energy of 100 mW $cm^{-2}$(meanwhile, 2.70% for DSSCs with FP2). The conversion efficiency is increased by 1.3 times.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.243-247
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• 2012

A ruthenium (Ru) catalytic layer and a conventional Pt layer were assessed as counter electrodes (CE) for dye sensitized solar cells (DSSCs). Ru films with different thicknesses of 34, 46, and 90 nm were deposited by atomic layer deposition (ALD). Pt layers with the same thicknesses were prepared by sputtering. $0.45cm^2$ DSSCs were prepared and their properties were characterized by FE-SEM, cyclic voltammetry (CV), impedance spectroscopy (EIS), and current-voltage (I-V). FE-SEM revealed that the crystallized Ru films and Pt films had been deposited quite conformally. CV showed that the catalytic activity of Pt was much greater than that of Ru. In addition, although the catalytic activity of Pt did not depend on the thickness, that of Ru showed an increase with increasing thickness. Impedance analysis revealed high charge transfer resistance at the Ru interface and a decrease with increasing Ru thickness, whereas Pt showed low resistance with no thickness dependence. Despite the relatively small catalytic activity of Ru, the I-V result revealed the average energy conversion efficiency of Ru and Pt to be 2.98% and 6.57%, respectively. These results suggest that Ru can be used as counter electrodes in DSSCs due to its extremely low temperature process compatibility.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.356-360
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• 2007

Recently, dye sensitized solar cells (DSSCs) composed of nanoporous $TiO_2$, light-sensitive dyes, electrolytes, and counter electrode have been received much attention. Nanostructured particles with higher surface area for the higher adsorption of Ru (II) dye are required to increase the quantity of light absorption. Also, it has been reported that the key factor to achieve high energy conversion efficiency in the photoelectrode of DSSC is the heat treatment of $TiO_2$ paste with acid addition. In this work, we investigated the influence of acid treatment of $TiO_2$ solar cell on the photovoltaic performance of DSSC. The working electrodes fabricated in this work were characterized by X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), field emission scanning electron microscope (FE-SEM), and atomic force microscope (AFM). In addition, the influence of nanostructured photoelectrode fabricated with the acid-treated paste on the energy conversion efficiency was investigated on the basis of photocurrent-potential curves. It was found that the influence of acid-treated paste on the photovoltaic efficiency was significant.

• Bulletin of the Korean Chemical Society
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• v.32 no.11
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• pp.4109-4112
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• 2011