• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.574-577
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• 2011

In this study, we use the $2.5cm{\times}7.5cm$ soda lime glass as the substrate. We used the ultrasonicator. Glass was dipped in the acetone, methanol and DI water respectively for 10 minutes. Ar(99.99%)gas was used as the sputtering gas. We varied the RF power between 100~175 W with 25 W steps. Base pressure was kept by turbo molecular pump at $3.0{\times}10^{-6}$ torr. Working pressure was kept by injection of Ar gas. ZnS thin films were deposited with the radio frequency magnetron sputtering technique at various temperatures and sputtering powers. It is also clearly observed that, the intensity of the (111) XRD peak increases with increasing the RF power. Electrical properties were measured by hall effect methods at room temperature. The resistivity, carrier concentration, and hall mobility of ZnS deposited on glass substrate as a function of sputtering power. It can be seen that as the sputtering power increase from 100 to 175 W, the resistivity of the films on glass decreased significantly from $8.1{\times}10^{-2}$ to $1.2{\times}10^{-3}\;{\Omega}{\cdot}cm$. This behavior could be explained by the effect of the sputtering power on the mobility and carrier concentration. When the RF power increases, the carrier concentration increases slightly while the resistivity decreases significantly. These variation originate from improved crystallinity and enhanced substitutional doping as the sputtering power increases.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.218-218
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• 2012

Nanocrystalline $SnO_2$ colloids are synthesized by hydrolysis of $SnCl_4{\cdot}5H_2O$ in aqueous ammonia solution. The synthesized $SnO_2$ nanoparticles with ca. 15 nm in diameter are coated on a fluorinedoped thin oxide (FTO) conductive substrate and heated at $550^{\circ}C$. The annealed $SnO_2$ film is treated with aqueous $TiCl_4$ solution, which is sensitzied with MK-2 dye (2-cyano-3-[5'''-(9-ethyl- 9H-carbazol-3-yl)-3',3'',3''',4-tetra-n-hexyl-[2,2',5',2'',5'',2''']-quater thiophen-5-yl]). Compared to bare $SnO_2$ film, the conversion efficiency is significantly improved from 0.22% to 3.13% after surface treatment of $SnO_2$ with $TiCl_4$, which is mainly due to the large increases in both photocurrent density from 1.33 to $9.46mA/cm^2$ and voltage from 315 to 634 mV. It is noted that little change in the amount of the adsorbed dye is detected from 1.21 for the bare $SnO_2$ to $1.28{\mu}mol/cm^2$ for the $TiCl_{4-}$ treated $SnO_2$. This indicates that the photocurrent density increased by more than 6 times is not closely related to the dye loading concentration. From the photocurrent and voltage transient spectroscopic studies, electron life time increases by about 13 order of magnitude, whereas electron diffusion coefficient decreases by about 3.6 times after $TiCl_4$ treatment. Slow electron diffusion rate offers sufficient time for regeneration kinetics. As a result, charge collection efficiency of about 40% before $TiCl_4$ treatment is improved to 95% after $TiCl_4$ treatment. The large increase in voltage is due to the significant increase in electron life time, associated with upward shift of fermi energy.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.458-458
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• 2013

We investigated a study on the thermal degradation of boron doped zinc-oxide (BZO) layer which used as a transparent conducting layer on the Cu (In1-xGax) Se2 (CIGS) based thin film solar cells. Devices were annealed under the temperature of $100^{\circ}C$ or 100 hours and then Hall measurement was carried out to characterize the parameters of mobility (${\mu}Hall$), resistivity (${\rho}$), conductivity (${\sigma}$) and sheet resistance (Rsh). The initial values of ${\mu}Hall$, ${\rho}$, ${\sigma}$ and Rsh were $29.3cm^2$/$V{\cdot}s$, $2.1{\times}10^{-3}{\Omega}{\cdot}cm$, $476.4{\Omega}^{-1}{\cdot}cm^{-1}$ and $19.1{\Omega}$/${\Box}$ respectively. After the annealing process, the values were $4.5cm^2$/$V{\cdot}s$, $12.8{\times}10^{-3}{\Omega}{\cdot}cm$, $77.9{\Omega}^{-1}{\cdot}cm^{-1}$ and $116.6{\Omega}$/${\Box}$ respectively. We observed that ${\mu}Hall$ and ${\sigma}$ were decreased, and ${\rho}$ and Rsh were increased. In this study, BZO layer plays an important role of conducting path for electrons generated by incident light onthe CIGS absorption layer. Therefore, the degradation of BZO layer characterized by the parameters of ${\mu}Hall$, ${\rho}$, ${\sigma}$ and Rsh, affect to the cell efficiency.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.125.2-125.2
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• 2011

CuInGaSe2 (CIGS)을 포함한 Chalcopyrite계 물질은 직접천이형 반도체이면서, ${\sim}1{\times}10^5cm^{-1}$ 이상의 광흡수계수를 보이며, 조성제어를 통한 밴드갭 조절이 가능해 차세대 고효율 박막태양전지재료로 매우 주목받고 있다. 최근, CIGS 박막태양전지 제조를 위해 CIGS 흡수층의 여러 가지 박막제조 공정들이 개발되고 있으나, 동시증착법과 소위 2단계법이라 일컬어지는 금속 전구체 스퍼터링 증착 후 셀렌화 공정을 가장 대표적인 공정이라 말 할 수 있다. 동시증착법은 실험실 수준의 소면적 셀에서 20%에 가까운 높은 효율의 CIGS 박막태양전지 제조에 성공하였음에도 불구하고, 상용화를 위한 대면적 셀 제조를 위해 해결해야 할 문제들이 아직 남아있다. 또한, 2단계법의 경우는 스퍼터링 공정을 기반으로 대면적 셀 제조에는 용이하나, CIGS/Mo 계면에서의 Ga 응집현상의 발생 및 셀렌화 공정에 사용되는 독성가스($H_2Se$)의 문제 등이 남아 있어 새로운 시각에서의 접근 방법이 요구되고 있다. 본 연구에서는 CIGS 4성분계 단일 타겟을 사용, RF 스퍼터링 공정을 통해 $200{\times}200mm^2$ 기판 위에 CIGS 박막을 제조하여 그 특성을 분석하였다. XRD 분석결과, 동시증착법에서 일반적으로 관찰되는 CIGS/Mo 계면에서의 $MoSe_2$ 상의 존재는 관찰되지 않았으며, CIGS 단일상의 다결정 박막이 제조되었음을 알 수 있었다. 또한, CIGS 박막제조 후, RTA 공정을 통해 CIGS 박막의 결정성이 향상됨을 관찰 할 수 있었으며, SIMS 분석결과, Mo층의 공정 조건에 따라 CIGS/Mo 계면에서의 금속원소 (In, Ga, Mo)의 상호확산이 크게 억제됨을 알 수 있었다. 그 외의 특성평가 결과들을 통하여 CIGS 4성분계 단일 타겟을 사용한 CIGS 박막태양전지 제조의 유용성에 대해 논의하고자 한다.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.676-680
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• 2010

Most TCOs such as ITO, AZO(Al-doped ZnO), FTO(F-doped $SnO_2$) etc., which have been widely used in LCD, touch panel, solar cell, and organic LEDs etc. as transparent electrode material reveal n-type conductivity. But in order to realize transparent circuit, transparent p-n junction, and introduction of transparent p-type materials are prerequisite. Additional prerequisite condition is optical transparency in visible spectral region. Oxide based materials usually have a wide optical bandgap more than ~3.0 eV. In this study, single-phase transparent semiconductor of $SrCu_2O_2$, which shows p-type conductivity, have been synthesized by 2-step solid state reaction at $950^{\circ}C$ under $N_2$ atmosphere, and single-phase $SrCu_2O_2$ thin films of p-type TCOs have been deposited by RF magnetron sputtering on alkali-free glass substrate from single-phase target at $500^{\circ}C$, 1% $H_2$/(Ar + $H_2$) atmosphere. 3% $H_2$/(Ar + $H_2$) resulted in formation of second phases. Hall measurements confirmed the p-type nature of the fabricated $SrCu_2O_2$ thin films. The electrical conductivity, mobility of carrier and carrier density $5.27{\times}10^{-2}S/cm$, $2.2cm^2$/Vs, $1.53{\times}10^{17}/cm^3$ a room temperature, respectively. Transmittance and optical band-gap of the $SrCu_2O_2$ thin films revealed 62% at 550 nm and 3.28 eV. The electrical and optical properties of the obtained $SrCu_2O_2$ thin films deposited by RF magnetron sputtering were compared with those deposited by PLD and e-beam.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.11-11
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• 2010

Thin-film-transistors (TFTs) that can be deposited at low temperature have recently attracted lots of applications such as sensors, solar cell and displays, because of the great flexible electronics and transparent. Transparent and flexible transistors are being required that high mobility and large-area uniformity at low temperature [1]. But, unfortunately most of TFT structures are used to be $SiO_2$ as gate dielectric layer. The $SiO_2$ has disadvantaged that it is required to high driving voltage to achieve the same operating efficiency compared with other high-k materials and its thickness is thicker than high-k materials [2]. To solve this problem, we find lots of high-k materials as $HfO_2$, $ZrO_2$, $SiN_x$, $TiO_2$, $Al_2O_3$. Among the High-k materials, $Al_2O_3$ is one of the outstanding materials due to its properties are high dielectric constant ( ~9 ), relatively low leakage current, wide bandgap ( 8.7 eV ) and good device stability. For the realization of flexible displays, all processes should be performed at very low temperatures, but low temperature $Al_2O_3$ grown by sputtering showed deteriorated electrical performance. Further decrease in growth temperature induces a high density of charge traps in the gate oxide/channel. This study investigated the effect of growth temperatures of ALD grown $Al_2O_3$ layers on the TFT device performance. The ALD deposition showed high conformal and defect-free dielectric layers at low temperature compared with other deposition equipments [2]. After ITO was wet-chemically etched with HCl : $HNO_3$ = 3:1, $Al_2O_3$ layer was deposited by ALD at various growth temperatures or lift-off process. Amorphous InGaZnO channel layers were deposited by rf magnetron sputtering at a working pressure of 3 mTorr and $O_2$/Ar (1/29 sccm). The electrodes were formed with electron-beam evaporated Ti (30 nm) and Au (70 nm) bilayer. The TFT devices were heat-treated in a furnace at $300^{\circ}C$ and nitrogen atmosphere for 1 hour by rapid thermal treatment. The electrical properties of the oxide TFTs were measured using semiconductor parameter analyzer (4145B), and LCR meter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.49-49
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• 2009

최근 범세계적인 그린에너지 정책에 관련해 화석연료를 대체할 수 있는 수소, 풍력, 태양광 등의 대체 에너지에 대한 관심이 고조되고 있다. 이러한 여러 대체에너지 중에서도 태양광을 전기에너지로 변환하는 태양전지에 관한 연구가 집중되고 있다. 태양전지는 구조적으로 단순하고 제조 공정도 비교적 간단하지만, 보다 널리 보급되기 위해서는 경제성 향상이라는 문제점을 해결해야 한다. 이를 위해서는 기존의 실리콘 태양전지를 대체할 수 있는 신물질에 대한 연구가 필요하며, 그 중에서도 반도체 기술을 이용한 박막형 태양전지는 기존의 실리콘 태양 전지가 가지고 있는 고비용이라는 문제점을 극복할 수 있을 것으로 기대를 모으고 있다. 박막형 태양전지의 박막 재료로는 CIGS, CdTe 등이 연구되어지고 있지만, 아직까지는 기존의 실리콘 태양전지에 비해 에너지변환효율이 낮은 이유로 인해 실용화가 많이 이루어지지 못하고 있는 것이 사실이다. 이러한 박막형 태양전지의 재료들 중에서도 CdTe는 이종접합 박막형 태양전지에 흡광층으로 사용되는 것으로 상온에서 1.45eV 정도의 밴드갭(band gap) 에너지를 갖는 II-VI족 화합물반도체로써 태양광 스펙트럼과 잘 맞는 이상적인 밴드랩 에너지와 높은 광흡수도 때문에 박막형 태양전지로 가장 주목을 받고 있다. CdTe 박막의 제조 방법으로는 진공증착법(vacuum evaporation), 전착법(electrodeposition), 스퍼터링법(sputtering) 등이 있지만 본 연구에서는 스퍼터링법을 이용하여 박막을 증착하였다. 이상과 같이 증착된 CdTe 박막을 화학적기계적연마(CMP, chemical mechanical polishing) 공정을 적용시킴으로써, 태양전지의 에너지변환효율에 직접적인 영향을 끼칠 수 있는 CdTe 박막의 물리적, 전기적 특성들의 변화를 연구하기 위한 선행 연구를 진행하였다. 특히 본 연구에서는 CdTe 박막의 화학적 기계적 연마 특성을 분석하여 정규화를 통한 모델링을 수행하였다. 또한 화학적기계적연마 공정 전과 후의 표면 특성을 관찰하기 위해 SEM(scanning electron microscopy)과 AFM(atomic forced microscope)를 이용하였으며, 구조적 특성 관찰을 XRD(X-ray diffraction)를 사용하여 실험을 수행하였다.

• Journal of the Korea Convergence Society
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• v.11 no.12
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• pp.97-103
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• 2020

This study sets the solar power system installed and applied to the vertical side wall among the photovoltaic systems in the building as the scope of the research. The theoretical background was considered through literature research as a research method, and the current status, trends and characteristics of solar generator design installed and applied to domestic and foreign vertical side walls were then investigated and analyzed cases. As a result, the importance and necessity of photovoltaic generators, potential for power generation and growth were identified, and positive factors and directions were found for improving aestheticity. Based on this point, we would like to propose expected effects that can be applied to photovoltaic system design installed and applied to vertical side walls in the future, and confirm the direction and significance of the improvement of aesthetic quality of the proposal for development of thin film solar cell design technology using green facade design.

• Bulletin of the Korean Chemical Society
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• v.32 no.spc8
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• pp.2899-2905
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• 2011

We have demonstrated that TPyPA can be used as an efficient multi-functional material for OLEDs; hole transporting material (HTL), blue and white-light emitter. The device based on TPyPA as the HTL exhibited an external quantum efficiency of 1.7% and a luminance efficiency of 4.2 cd/A; these values are 40% higher than the external quantum efficiency and luminance efficiency of the NPD-based reference device. The device based on TPyPA as a blue-light emitter exhibited an external quantum efficiency of 4.2% and a luminance efficiency of 5.3 $cdA^{-1}$ with CIE coordinates at (0.16, 0.14), the device based on TPyPA as a white-light emitter exhibited an external quantum efficiency of 3.2% and a luminance efficiency of 7.7 $cdA^{-1}$ with CIE coordinates at (0.33, 0.39). Also, TPyPA-based organic solar cell (OSC) exhibited a maximum power conversion efficiency of 0.35%. TPyPA-based organic thin-film transistors (OTFTs) exhibited highly efficient field-effect mobility (${\mu}_{FET}$) of $1.7{\times}10^{-4}cm^2V^{-1}s^{-1}$, a threshold voltage ($V_{th}$) of -15.9 V, and an on/off current ratio of $8.6{\times}10^3$.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.405-405
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• 2016

CIGS 박막 태양전지에서 완충층으로 사용되는 ZnS는 단파장 영역에서 높은 투과도와 CIGS 계면과의 좋은 접착을 가지고 친환경적이며 3.74eV의 에너지 밴드갭을 가지고 있기 때문에 CdS를 사용했을 때 보다 더 넓은 에너지 영역의 광자를 p-n 접합 경계 영역으로 통과 시킬 수 있고 Cd-free 물질이라는 점에서 기존의 CdS 완충층의 대체 물질로 각광 받고 있다. 본 연구에서는 CIGS 박막에 화학습식공정 방법을 이용하여 최적화된 ZnS 박막의 증착 조건을 찾기 위해 실험 변수인 시약의 농도, 실험온도, 열처리 조건 등의 다양한 변화를 통해 실험을 진행하였고, 박막의 갈라짐과 pin-hole 현상을 개선하고 균일한 막을 제조하기 위해 구연산 나트륨 농도에 따른 ZnS 박막의 특성을 연구하였다. 본 실험 결과로서 실험변수인 황산아연의 농도 0.15M, 암모니아는 0.3M, 티오요소 1M, 공정 온도 $80^{\circ}C$의 최적화 된 조건에서 가장 좋은 품질의 ZnS 박막을 제조하였지만, ZnS 박막의 열처리 후 산소의 양이 줄어감에 따라 박막의 표면이 갈라지고 pin-hole 현상이 발생하는 것을 확인할 수 있었다. 박막의 품질을 개선하기 위해 구연산 나트륨을 첨가하여 실험한 결과 구연산 나트륨의 0.05M의 농도에서는 박막 표면에 90nm의 갈라짐의 크기와 pin-hole 현상이 남아있는 것을 확인하였고, 농도가 높아질수록 점차 크기가 줄어들면서 0.4M에서는 갈라짐이 거의 없는 표면과 pin-hole 현상도 없어지는 것을 확인하였고, 약 144nm의 박막 두께와 3.8eV의 에너지 밴드갭을 가지고, 약 81%의 높은 광투과율을 갖는 고품질의 ZnS 박막을 제작할 수 있었다.