Gyeonggi, South Korea
Gyeonggi, South Korea

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Liu Z.,Gachon University | Liu Z.,Gachon Bio Nano Research Institute | Liu Z.,Zhangjiagang Kangde Xin Optronics Material Co. | Seo S.,Gachon University | And 3 more authors.
Journal of Applied Polymer Science | Year: 2017

Morphology control is an important issue for boosting the performance of organic bulk-heterojunction (BHJ) solar cells. In this study, we investigated the correlation between alcohol solvents and the morphologies of poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′] dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) and [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM)-based organic solar cells by spin-casting the alcohol onto the active layers. We found that the morphologies strongly depended on the structure of the alcohol [alkyl chain length and hydroxyl (OH) group position]. Ethanol or 2-propanol showed the highest performance among the alcohols considered here. Atomic force microscopy images and absorption spectra demonstrated that the alcohols affected the morphologies of PC70BM rather than those of PTB7. The morphologies of PC70BM were dependent on the solubilities of the alcohols to the active layers and the hydrogen-bonding strengths between the PC70BM and alcohol molecules. Our results indicate that the use of alcohols for solvent annealing is a simple and efficient method for developing high-performance organic BHJ solar cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44367. © 2016 Wiley Periodicals, Inc.


Tian T.,Gachon University | Tian T.,Gachon Bio Nano Research Institute | Li Z.,Gachon University | Li Z.,Gachon Bio Nano Research Institute | And 2 more authors.
Biosensors and Bioelectronics | Year: 2014

We developed a simple and sensitive method for sequence-specific DNA detection using functionalized graphene (FG) and methylene blue (MB). Target DNA with a specific sequence was identified by differential-pulse voltammetry, which produces a change in the redox currents of the incorporated MB. FG played a critical role in enhancing the sensitivity of DNA detection and reduced the concentration of MB substantially near the electrodes when the sequence of the target DNA was not complementary to that of the probe by adsorbing the single-stranded DNA with the bound MB, and sinking. Our system could detect even single base-pair mismatches between the target and probe. Fabricating this system does not involve a laborious probe-immobilization process and is considerably simpler than fabricating graphene-electrode-based DNA sensors. © 2013 Elsevier B.V.


Liu Z.,Gachon University | Liu Z.,Gachon Bio Nano Research Institute | Seo S.,Gachon University | Seo S.,Gachon Bio Nano Research Institute | And 2 more authors.
Applied Physics Letters | Year: 2013

We find that the doping of Cr2O3 nanoparticles into organic bulk-heterojunction solar cells leads to the power conversion efficiency improvements of 15.9%-22.8%, which are larger than or comparable to those obtained using other metal oxide nanostructures in previous studies. The light absorptions at long-wavelength regions and the electron mobilities are enhanced; these enhancement increased the short-circuit current and fill factor. The increased shunt resistance suggests that the hole leakage current may be suppressed. This suppression subsequently enhances the fill factor. Thus, the incorporation of Cr2O3 nanoparticles is a simple and efficient technique for improving bulk-heterojunction devices. © 2013 AIP Publishing LLC.


Liu Z.,Gachon University | Liu Z.,Gachon Bio Nano Research Institute | Ju H.,Gachon Bio Nano Research Institute | Ju H.,Gachon University | And 2 more authors.
Applied Physics Letters | Year: 2013

The use of 1,8-diiodooctane (DIO) as a solvent additive in poly[N-9′-heptadecanyl-2,7-carbazole-alt-5, 5-(4′,7′-di-2- thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT)-based bulk-heterojunction solar cells increased the power conversion efficiency (PCE) by 20.9%. This improvement was due to the increase in the fill factor and open-circuit voltage (Voc), which compensated for the decrease in the short-circuit current (Jsc). DIO had the opposite effect, increasing Jsc and decreasing Voc, in the devices using other low-band gap polymers. The best sample in this study showed a PCE of 6.27% and Voc of 939 mV, indicating that the fabricated device is an efficient solar cell with a high Voc close to 1 V. © 2013 AIP Publishing LLC.


Li J.,Gachon University | Li J.,Gachon Bio Nano Research Institute | Lee E.-C.,Gachon University | Lee E.-C.,Gachon Bio Nano Research Institute
Biosensors and Bioelectronics | Year: 2015

All-solution-processed, easily-made, flexible multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS)-based electrodes were fabricated and used for electrochemical DNA sensors. These electrodes could serve as a recognition layer for DNA, without any surface modification, through π-π interactions between the MWCNTs and DNA, greatly simplifying the fabrication process for DNA sensors. The electrodes were directly connected to an electrochemical analyzer in the differential pulse voltammetry (DPV) and cyclic voltammetry (CV) measurements, where methylene blue was used as a redox indicator. Since neither functional groups nor probe DNA were immobilized on the surfaces of the electrodes, the sensor can be easily regenerated by washing these electrodes with water. The limit of detection was found to be 1.3×102pM (S/N=3), with good DNA sequence differentiation ability. Fast fabrication of a DNA sensor was also achieved by cutting and attaching the MWCNT-PDMS composite electrodes at an analyte solution-containable region. Our results pave the way for developing user-fabricated easily attached DNA sensors at low costs. © 2015 Elsevier B.V.


Liu Z.,Gachon University | Liu Z.,Gachon Bio Nano Research Institute | Lee E.-C.,Gachon University | Lee E.-C.,Gachon Bio Nano Research Institute
Organic Electronics: physics, materials, applications | Year: 2015

In this work, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) was improved by 14.8% (from 11.09% to 12.73%) by using 1,8-diiodooctane (DIO) as a solvent additive during the deposition of phenyl-C61-butyric acid methyl ester (PCBM) layers. The primary reasons for the PCE improvement are the simultaneous increases in the short-circuit current density, fill factor, and open-circuit voltage. The incorporation of DIO improves the morphology of the electron transport layer (PCBM), which plays an important role in charge dissociation, transportation, and collection. Our results indicate that engineering the morphology of the electron transport layer is a simple and effective method for developing high-performance PSCs. © 2015 Elsevier B.V. All rights reserved.


Liu Z.,Gachon University | Liu Z.,Gachon Bio Nano Research Institute | Lee S.Y.,Korea Institute of Science and Technology | Lee S.Y.,Korean University of Science and Technology | And 2 more authors.
Applied Physics Letters | Year: 2014

By embedding copper nanoparticles into poly(3,4-thylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layers, the power conversion efficiency of organic bulk-heterojunction solar cell using poly(3-hexylthiophene) (P3HT) was increased from 3.58% to 3.96%, and that of the device based on poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7) was increased from 6.79% to 7.43%. The copper nanoparticles enhanced light harvesting efficiency because of their localized surface plasmon resonance effects. This improved short circuit current densities, the dominant reason for the improvement in performance. Our results indicate that copper nanoparticles are cost-effective plasmonic materials for organic bulk-heterojunction solar cells as compared with gold and silver nano-structures. © 2014 AIP Publishing LLC.

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