• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.193-193
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• 2013

실리콘 박막 태양전지는 광 흡수층에서 형성된 정공과 전자를 효과적으로 분리하기 위해 p형과 n형으로 도핑된 층을 형성하는 p-i-n구조를 갖게 된다. 이러한 도핑 층을 형성하기 위해 B2H6와 PH3와 같은 독성 가스를 사용하기 때문에, 공정 안정성과 환경적인 이슈가 대두된다. 또한 도핑은 추가적으로 실리콘 박막 태양전지의 안정화 효율을 지속적으로 저하시키는 요인이 된다. 이러한 문제점을 개선하기 위하여, 창층으로 MoO3, V2O5, WO3 등과 같이 높은 일함수를 갖는 전이금속 산화물을 사용하고, 광 흡수층으로 i-Si:H을, 후면 전극으로 낮은 일함수를 나타내는 LiF/Al을 사용하였다. 전이금속 산화물과 LiF/Al의 큰 일함수 차이에 의해서 흡수층인 i-Si:H 에서 생성된 캐리어들은 효과적으로 분리되고 수집이 된다. 금속 산화물은 스퍼터링 공정에 의하여 이루어졌으며, 스퍼터링 공정조건에 따라 산화도가 조절되며, 이러한 산화도에 따라 태양전지의 셀 특성이 결정된다. 도핑 층이 없는 새로운 형태의 실리콘 박막 태양전지는 기존 비정질 실리콘 박막 태양전지에 비해 높은 안정화 효율을 나타내며, 이는 도핑 층이 없기 때문에 기존 실리콘 박막 태양전지의 열화현상에 따른 효율저하가 발생하지 않는 장점을 지내고 있다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.286-286
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• 2011

최근 폴리머를 기판으로 하는 Flexible TFT (thin film transistor)나 3D-ULSI (three dimensional ultra large-scale integrated circuit)에서 높은 에너지 소비효율과, 빠른 반응 속도를 실현 시키기 위해 낮은 비저항(resistivity)을 가지며, 높은 홀 속도(carrier hall mobility)를 가지는 다결정 반도체 박막(poly-crystalline thin film)을 만들고자 하고 있다. 이를 실현 시키기 위해서는 높은 온도에서 장시간의 열처리가 필요하며, 이는 폴리머 기판의 문제점을 야기시킬 뿐 아니라 공정시간이 길다는 단점이 있었다. 이에 반도체 박막의 재결정화 온도를 낮춰주는 metal (Al, Ni, Co, Cu, Ag, Pd etc.,)을 이용하여 결정화 시키는 방법이 많이 연구 되어지고 있지만, 이 또한 재결정화가 이루어진 반도체 박막 안에 잔여 금속(residual metal)이 존재하게 되어 비저항을 높이고, 홀 속도를 감소시키는 단점이 있다. 이에 본 실험은 HiPIMS (High power impulse magnetron sputtering)와 PIII and D (plasma immersion ion implantation and deposition) 공정을 복합시킨 프로세스로 적은양의 금속이온주입을 통하여 재결정화 온도를 낮췄을 뿐 아니라, 잔여 하는 금속의 양도 매우 적은 다결정 반도체 박막을 만들 수 있었다. 분석 장비로는 박막의 결정화도를 측정하기 위해 GAXRD (glancing angle X-ray diffractometer)를 사용하였고, 잔여 하는 금속의 양과 화학적 결합 상태를 알아보기 위해 XPS를 통해 분석을 하였다. 마지막으로 홀 속도와 비저항을 측정하기 위해 Hall measurement와 Four-point prove를 사용하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.217-217
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• 2012

Solution-processed tungsten oxide thin film with thickness of about 30 nm is prepared from ammonium tungstate. This layer is introduced into the interface between the poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) layer and the ITO electrode to be used as an electron blocking layer. The annealed tungsten oxide thin films at $150^{\circ}C$ and $300^{\circ}C$ show amorphous phase, while the $400^{\circ}C$ -annealed tungsten oxide film shows crystalline phase. At $150^{\circ}C$ annealing temperature, the conversion efficiency is significantly improved from 0.71% to 1.42% as the condition is changed from vacuum to air atmosphere, which is related to oxidation state of tungsten in amorphous phase. For the air annealing condition, the conversion efficiency is further increased from 1.42% to 2.01% as the temperature is increased from $150^{\circ}C$ to $300^{\circ}C$, which is mainly due to the removal of the chemisorbed water. However, a slight deterioration in photovoltaic performance is observed when the temperature is increased to $400^{\circ}C$, which is ascribed to poor electron blocking ability due to the formation of crystalline phase. It is concluded that $W^{6+}$ oxidation state and amorphous nature in tungsten oxide interlayer is essential for blocking electron effectively from the active layer to the ITO electrode.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.161-161
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• 2011

Titanium (IV) dioxide (TiO2) is one of the most attractive d-block transition metal functional oxides. Many applications of TiO2 such as dye-sensitized solar cells and photocatalyst have been widely investigated. To utilize solar energy efficiently, TiO2 should be well-aligned with a high surface area and promote the charge separation as well as electron transport. Herein, the TiO2 nanotubes were successfully fabricated by a template-directed method. The electrospun PEO(Polyethylene oxide, Molecular weight, 400k)fibers were used as a soft template for coating with titanium dioxide using an atomic layer deposition (ALD) technique. The deposition was conducted onto a template at 50$^{\circ}C$ by using titaniumisopropoxide [Ti(OCH(CH3)2)4; TTIP] as precursors of TiO2. While the as-deposited TiO2 layers onto PEO fibers were completely amorphous with atomic layer deposition, the TiO2 layers after calcination at 500$^{\circ}C$ for 1 h were properly converted into polycrystalline nanostructured hallow TiO2 nanotube. The TiO2 nanotube with high surface area can be easily handled and reclaimed for use in future applications related to solar cell fabrications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.127-127
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• 2009

The most important part of the fabrication solar cells is the anti-reflection coating when excludes the kinds of silicon substrates (crystalline, polycrystalline, or amorphous), patterns and materials of electrodes. Anti-reflection coatings reduce the reflection of sunlight and at last increase the intensity of radiation to inside of solar cells. So, we can obtain increase of solar cell efficiency about 10% using anti-reflection coating. There are many kinds of anti-reflection film for solar cell, such as SiN, $SiO_2$, a-Si, and so on. And, they have two functions, anti-reflection and passivation. However such materials could not perfectly prevent reflection. So, in this work, we investigated the anti-reflection coating with the columnar structure ZnO thin film. We synthesized columnar structure ZnO film on glass substrates. The ZnO films were synthesized using a RF magnetron sputtering system with a pure (99.95%) ZnO target at room temperature. The anti-reflection coating layer was sputtered by argon and oxygen gases. The angle of target and substrate measures 0, 20, 40, 60 degrees, the working pressure 10 mtorr and the 250 W of RF power during 40 minutes. The confirm the growth mechanism of ZnO on columnar structure, the anti-reflection coating layer was observed by field emission scanning electron microscopy (FE-SEM). The optical trends were observed by UV-vis and Elleso meter.

• Current Photovoltaic Research
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• 제7권4호
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• pp.97-102
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• 2019

Bifacial and semitransparent hydrogenated amorphous silicon (a-Si:H) thin-film solar cells in p-i-n configuration were prepared with front and rear transparent conducting oxide (TCO) electrodes using plasma-enhanced chemical vapor deposition method. Fluorine-doped tin oxide and tin-doped indium oxide films were used as front and rear TCO contacts, respectively. Film thickness of intrinsic a-Si:H absorber layers were controlled from 150 nm to 450 nm by changing deposition time. The dependence of performance characteristics of solar cells on the front and rear illumination direction were investigated. For front illumination, gradual increase in the short-circuit current density (J_SC) from 10.59 mA/㎠ to 14.19 mA/㎠ was obtained, whereas slight decreases from 0.83 V to 0.81 V for the open-circuit voltage (V_OC) and from 68.43% to 65.75% for fill factor (FF) were observed. The average optical transmittance in the wavelength region of 380 ~ 780 nm of the solar cells decreased gradually from 22.76% to 15.67% as the absorber thickness was changed from 150 nm to 450 nm. In case of the solar cells under rear illumination condition, the J_SC increased from 10.81 to 12.64 mA/㎠ and the FF deceased from 66.63% to 61.85%, while the V_OC values were maintained at 0.80 V with increasing the absorber thickness from 150 nm to 450 nm. By optimizing the deposition parameters, a high-quality bifacial and semitransparent a-Si:H solar cell with 350 nm-thick i-a-Si:H absorber layer exhibited the conversion efficiencies of 7.69% for front illumination and 6.40% for rear illumination, and average visible optical transmittance of 17.20%.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.45-48
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• 2009

This study evaluated the influence of temperature on the PV module surface on power output characteristics, especially for an amorphous transparent thin-film PV module which was applied to a full-scale mock-up model as building integrated photovoltaic system. The tested mock-up consisted of various slopes of PV module, facing to the south. The annual average temperature of the module installed with the slope of $30^{\circ}$ revealed $43.1^{\circ}C$, resulting in $7^{\circ}C$ higher than that measured in PV modules with the slope of $0^{\circ}$and $90^{\circ}$ did. This $30^{\circ}$ inclined PV module also showed the highest power output of 28.5W (measured at 2 PM) than other two modules having the power output of 20.4W and 14.9W in the same time for $0^{\circ}$ and $90^{\circ}$ in the slope, respectively. In case of the $30^{\circ}$ inclined PV module, it exhibited very uniform distribution of power output generation even under the higher temperature on the module surface. Consequently, the surface temperature of the PV module analyzed in this study resulted in 0.22% reduction in power output in every $1^{\circ}C$ increase of the module surface temperature.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.480.1-480.1
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• 2014

In this study, we suggest the new emitter formation applied solid phase epitaxy (SPE) growth process using rapid thermal process (RTP). Preferentially, we describe the SPE growth of intrinsic a-Si thin film through RTP heat treatment by radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD). Phase transition of intrinsic a-Si thin films were taken place under $600^{\circ}C$ for 5 min annealing condition measured by spectroscopic ellipsometer (SE) applied to effective medium approximation (EMA). We confirmed the SPE growth using high resolution transmission electron microscope (HR-TEM) analysis. Similarly, phase transition of P doped a-Si thin films were arisen $700^{\circ}C$ for 1 min, however, crystallinity is lower than intrinsic a-Si thin films. It is referable to the interference of the dopant. Based on this, we fabricated 16.7% solar cell to apply emitter layer formed SPE growth of P doped a-Si thin films using RTP. We considered that is a relative short process time compare to make the phosphorus emitter such as diffusion using furnace. Also, it is causing process simplification that can be omitted phosphorus silicate glass (PSG) removal and edge isolation process.

• 한국재료학회지
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• 제29권5호
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• pp.322-327
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• 2019

Hole carrier selective MoOx film is obtained by atomic layer deposition(ALD) using molybdenum hexacarbonyl[$Mo(CO)_6$] as precursor and ozone($O_3$) oxidant. The growth rate is about 0.036 nm/cycle at 200 g/Nm of ozone concentration and the thickness of interfacial oxide is about 2 nm. The measured band gap and work function of the MoOx film grown by ALD are 3.25 eV and 8 eV, respectively. X-ray photoelectron spectroscopy(XPS) result shows that the $Mo^{6+}$ state is dominant in the MoOx thin film. In the case of ALD-MoOx grown on Si wafer, the ozone concentration does not affect the passivation performance in the as-deposited state. But, the implied open-circuit voltage increases from $576^{\circ}C$ to $620^{\circ}C$ at 250 g/Nm after post-deposition annealing at $350^{\circ}C$ in a forming gas ambient. Instead of using a p-type amorphous silicon layer, high work function MoOx films as hole selective contact are applied for heterojunction silicon solar cells and the best efficiency yet recorded (21 %) is obtained.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권5호
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• pp.237-241
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• 2004

Amorphous silicon (a-Si) films are used in a broad range of solar cell, flat panel display, and sensor. Because of the greater ease of deposition and lower processing temperature, thin films are widely used for thin film transistors (TFTs). However, they have lower stability under the exposure of visible light and because of their low field effect mobility ($\mu$$_{FE}$ ) , less than 1 c $m^2$/Vs, they require a driving IC in the external circuits. On the other hand, polycrystalline silicon (poly-Si) thin films have superiority in $\mu$$_{FE}$ and optical stability in comparison to a-Si film. Many researches have been done to obtain high performance poly-Si because conventional methods such as excimer laser annealing, solid phase crystallization and metal induced crystallization have several difficulties to crystallize. In this paper, a new crystallization process using a molybdenum substrate has been proposed. As we use a flexible substrate, high temperature treatment and roll-to-roll process are possible. We have used a high temperature process above 75$0^{\circ}C$ to obtain poly-Si films on molybdenum substrates by a rapid thermal annealing (RTA) of the amorphous silicon (a-Si) layers. The properties of high temperature crystallized poly-Si studied, and poly-Si has been used for the fabrication of TFT. By this method, we are able to achieve high crystal volume fraction as well as high field effect mobility.