• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.235-235
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• 2013

We reported on the characteristics of organic solar cells (OSCs) fabricated on $HNO_3$-treated multilayer graphene (MLG) transparent electrodes. MLG electrodes were prepared using a chemical vapor deposition and a multi-transfer process. Compared to organic solar cells (OSCs) on the ITO electrodes had a fill factor of 65.97%, and a power conversion efficiency (PCE) of 3.364%, OSCs on the MLG (three-layer graphene) electrodes with sheet resistance of $274{\pm}1{\Omega}$/square and transparency of 92.1% had a fill factor of 43.46%, and a power conversion efficiency (PCE) of 2.019%. However, OSCs on the HNO3-treated MLG electrodes with lower sheet resistance of $119{\pm}1{\Omega}$/square had a fill factor of 57.54%, and a PCE of 2.861%. The results would provide a promising method to improve the performance of large-area OSCs based on MLG electrodes.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.408.2-409
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• 2016

Theoretically, the dye-sensitized solar cells (DSSCs) are high efficiency solar cells. However DSSCs have low power conversion efficiency (PCE) than silicon based solar cells. In this study, we use the phosphor materials, such as $Y_2O_3:Eu$ (Red), $Zn_2SiO_4:Mn$ (Green), $BaMgAl_{14}O_{23}:Eu$ (Blue), to enhance the PCE of DSSCs. Three phosphors were prepared and used as an effective scattering layer on the transparent $TiO_2$ with doctor blade method. We confirmed that the three scattering layers improve the PCE and Jsc due to the light harvesting enhancement via increased the scattering and absorbance in visible range. Under the sun illumination AM 1.5 conditions, the PCE of the mesoporous $TiO_2$ based DSSCs is 5.18 %. The PCE of the DSSCs with Y2O3:Eu, $Zn_2SiO_4:Mn$ and $BaMgAl_{14}O_{23}:Eu$ as scattering layer were enhanced to 5.66 %, 5.72% and 5.82%, respectably. In order to compare the optical properties change, DSSCs were measured by EQE, reflectance and PCE. At the same time, FE-SEM and XRD were used to confirm the structural changes of each layer.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1091-1097
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• 2013

This paper presents a rectifier with comparator using unbalanced body biasing in $0.11{\mu}m$ RF CMOS process. It is composed of MOSFETs and two comparators. The comparator is used to reduce reverse leakage current which occurs when the load voltage is higher than input voltage. For the comparator, unbalanced body biasing is devised. By using unbalanced body biasing, reference voltage for comparator changing from high state to low state is increased, and it reduces time interval for leakage current to flow. 13.56 MHz 2 Vpp signal is used for input and $1k{\Omega}$ resistor and 1 nF capacitor are used for output load for simulation and experimental environment. In simulation environment, voltage conversion efficiency(VCE) is 87.5 % and Power conversion efficiency(PCE) is 50 %. When the rectifier is measured, VCE shows 90.203 % and PCE shows 45 %.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.432.1-432.1
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• 2016

We demonstrated that the power conversion efficiency (PCE) of bilayer solar cell was significantly enhanced by inserting interfacial layer between the organic bilayer film and the Al electrode. Moreover, the water contact angle shows that the bilayer solar cells suffer from the undesirable surface component which limits the charge transport to the Al electrode. The AFM measurement has revealed that the pre- and post-thermal annealing treatments results in different morphologies of the interfacial layer which is critical for the higher PCE of the bilayer solar cells. Furthermore we have investigated the electrical properties of the bilayer solar cells and obtained insights into the detailed device mechanisms. The transient photovoltage measurements suggests that the significantly enhanced Voc is caused by reducing the recombination at the interface between the organic films and the Al electrode. By inserting the TiO2 layer between the bilayer film and Al electrode, the open circuit voltage (Voc) was increased from 0.37 to 0.66V. Consequently, the power conversion efficiency (PCE) of bilayer solar cells was significantly enhanced from 1.23% to 3.71%. As the results, the TiO2 interfacial layer can be used to form an ohmic contact layer, serveing as a blocking layer to prevent the penetration of the Al, and to reduce the recombination at the interface.

• Vacuum Magazine
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• v.1 no.4
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• pp.10-13
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• 2014

Since the development of 9.7% efficient long-term stable solid state perovskite solar cell in 2012, intensive study on perovskite solar cell has been performed. As a result, power conversion efficiency (PCE) has reached 20.1%. In-dept study on perovskite light absorber enabled understanding of origin of superb photovoltaic performance of perovskite solar cell. In this article, historical evolutions of perovskite solar cell along with key physical properties enabling high PCE are presented. Several important results for development of high efficiency perovskite solar cell are introduced. Finally, in-present research issues and future direction for solving these issues are discussed.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1557-1559
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• 2009

By using optimum doping ratio (10 ~ 20 wt%) of glycerol, the power conversion efficiency (PCE) of organic photovoltaic devices based on poly (3-hexylthiophene) and phenyl-$C_{61}$-butyric acid methyl ester was dramatically increased from 3.23% to 5.03%. Finally, semitransparent organic photovoltaic devices including glycerol doped poly (3,4-ethylenedioxy-thiophene):poly (styrene sulfonate) and thin Ag (< 1 nm) buffer layer typically have shown PCE > 3% with transmittance > 30% in visible ranges.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.190.2-190.2
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• 2014

We report the origin of the improvement of the power conversion efficiency (PCE) of hybrid thin-film solar cells when a soluble C60 derivative, [6,6]-phenyl-$C_{61}$-butyric acid methyl ester (PCBM), is introduced as a hole-blocking layer. The PCBM layer could establish better interfacial contact by decreasing the reverse ark-saturation current density, resulting in a decrease in the probability of carrier recombination. The power conversion efficiency of this optimized device reached a maximum value of 8.34% and is the highest yet reported for hybrid thin-film solar cells.

• Journal of the Semiconductor & Display Technology
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• v.8 no.3
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• pp.1-5
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• 2009

In this study, we have shown the power conversion efficiency of organic thin film photovoltaic devices utilizing a conjugated polymer/fullerene bulk-hetero junction structure. We use MDMO-PPV(Poly[2-methoxy-5-(3,7-dimethyloctyloxy -1,4-phenylenevinylene) as an electron donor, PCBM([6,6]-Phenyl C61 butyric acid methyl ester) as an electron accepter, and PEDOT:PSS used as a HTL(Hole Transport Layer). We have fabricated OPV(Organic Photovoltaic) devices as a function of the MDMO-PPV/PCBM concentration from 1:1 to 1:5. The electrical characteristics of the fabricated devices were investigated by means of I-V, P-V, F·F(Fill Factor) and PCE(power conversion efficiency). The power conversion efficiency was gradually increased until 1:4 ratio, also the highest efficiency of 0.4996% was obtained at the ratio.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.243.1-243.1
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• 2015

To replace the based on silicon solar cells, the third generation solar cells, Dye-sensitized solar cells (DSSCs), is low fabrication than silicon solar cells, environmentally friendly and can be applied to various field. For this reason, the DSSCs have been continuously researched. But DSSCs have one drawback that is the low power conversion efficiency (PCE) than silicon solar cells. To solve the problem, we used the backr-eflector the Al foil that can be easily obtained from the surrounding in order to improve the efficiency of the DSSCs. Easily detachable Al foil back-reflector increases the photocurrent by enhancing the harvesting light because the discarded light is reused. It also leads to enhance the power conversion efficiency (PCE). In addition, we compared with the efficiency of the DSSCs that is applied and does not be applied with back-reflector according to the thickness of the TiO2 photoelectrode. When the back-reflector is applied to DSSCs, the photocurrent is increased. It leads to affect the efficiency. We used to solar simulator and Electrochemical Impedance Spectroscopy (EIS) to confirm the PCE and resistance. The DSSCs were also measured by External Quantum effect (EQE). At the same time, FE-SEM and XRD were used to confirm the thickness of layer and crystal structural of photoelectrode.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.11
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• pp.104-108
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• 2012

Flexible organic thin film solar cell device with Bulk Hetero-Junction (BHJ) structure was fabricated with blended conjugated polymer of PCDTBT : $PC_{71}BM$ as active layer. Surface of ITO anode for the organic solar cell device was treated with ozone. The organic solar cell device with bare ITO showed short circuit current density ($J_{sc}$) of $8.2mA/cm^2$, open-circuit voltage ($V_{oc}$) of 0.73V, fill factor (FF) of 0.36, and power conversion efficiency (PCE) of 2.16%, respectively. The organic solar cell device with ozone treated ITO anode revealed distinctively improved performance parameters:$J_{sc}$ of $9.8mA/cm^2$, $V_{oc}$ of 0.82V, FF of 0.43, PCE(${\eta}$) of 3.42%.