• 대한화학회지
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• 제63권5호
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• pp.352-359
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• 2019

The most important parameter of organic molecules for energy harvesting application focuses mainly on their band gap (HOMO-LUMO). In this report, we synthesized differently substituted 1,3,5-triazine based organic molecule which on future processing can be used in organic electronics like solar cells and OLED's. The energy gap of the synthesized novel analogue was calculated using cyclic voltammetry, UV-Visible spectroscopy and compared with density functional theory (DFT) studies.

• 전력전자학회논문지
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• 제24권3호
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• pp.147-152
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• 2019

With the recent emphasis on the importance of energy conservation, studies on high-efficiency elevator systems are being continuously conducted. Therefore, pulse width modulation converters are commonly used in traction drives on elevator systems. Wide bandgap devices have been increasingly commercialized, and their application to power conversion systems, such as renewable and energy storage system, has been gradually increasing. In this study, a SiC inverter for an elevator traction drive is investigated. In particular, an inverter is designed to minimize stray and parasitic inductance. Input and output filters are designed by considering switching frequency. The designed SiC inverter reduces volume by approximately 32% compared with that of a Si inverter, and power converter efficiency is over 98.8%.

• 한국진공학회지
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• 제18권2호
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• pp.127-132
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• 2009

Sb에 기초한 응력 초격자 적외선검출소자의 구성 물질인 도핑하지 않은 기판 GaSb 결정과 GaSb/SI-GaAs 박막에 잔존하고 있는 진성결함 (intrinsic defect)을 비교 조사하였다. 상온 근처 (250 K)까지 광여기 발광 (PL)을 보이는 GaSb 결정에서의 발광 에너지의 온도의존성으로부터, 밴드갭 에너지에 관한 경험식인 Varshni 함수의 파라미터 ($E_o$, $\alpha$, $\beta$)를 결정하였다. GaAs 기판 위에 성장된 이종 GaSb 박막에서는 GaSb 주요 진성결함으로 알려져 있는 29 meV의 이온화 에너지를 가지는 위치반전 (antisite) Ga ([$Ga_{Sb}$]) 결함과 함께 위치반전 Sb ([$Sb_{Ga}$])와의 복합결함 ([$Ga_{Sb}-Sb_{Ga}$])과 관련된 것으로 분석된 732/711 meV의 한 쌍의 깊은준위 (deep level)가 관측되었다. PL의 온도 및 여기출력 의존성을 분석하여, Sb-rich상태에서 성장된 GaSb 박막에서는 잉여 Sb의 자발확산 (self-diffusion)에 의하여 치환된 위치전도 [$Ga_{Sb}$] 및 [$Sb_{Ga}$]가 결합하여 [$Ga_{Sb}-Sb_{Ga}$]의 깊은준위를 형성하는 것으로 해석되었다.

• 한국전기전자재료학회논문지
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• 제25권8호
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• pp.664-669
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• 2012

Nano-structured one-dimensional $Na_2Ti_6O_{13}$ particles were synthesized by a molten salt process. Effects of processing parameters on the microstructure and band gap energy of the $Na_2Ti_6O_{13}$ powder were studied in this paper. For the synthesis of the $Na_2Ti_6O_{13}$ particles, two different raw materials of tubular shaped Na-titanate (Na-TiNT) and spherical shaped $TiO_2$ were utilized. Synthesizing with the raw material of Na-TiNT, around 70nm thick 1D-$Na_2Ti_6O_{13}$ with the bandgap energy of 3.5 eV was obtained at $810^{\circ}C$. Below $810^{\circ}C$ or without the presence of NaCl, 1D-$Na_2Ti_6O_{13}$ was in a relatively short in length and agglomerated state. With the processing temperature increased, the thickness of the 1D-$Na_2Ti_6O_{13}$ was also observed to be increased. On the other hand, when $TiO_2$ was employed as a raw material, the mixed amount of $Na_2CO_3$ played an important role in transforming the morphology and phase of the raw material, affecting the bandgap energy of the synthesized product. Specific surface area of the synthesized 1D-$Na_2Ti_6O_{13}$ was significantly affected by the raw and mixed materials as well as processing temperature. When Na-TiNT was processed at $810^{\circ}C$ with NaCl, the specific surface area of the 1D-$Na_2Ti_6O_{13}$ showed the best value of 30.63 $m^2/g$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.390.1-390.1
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• 2016

The present work explains the interfacial energetics of all oxide transparent photodiodes. The optical, structural and morphological of copper oxides were systematically analyse by UV-Visible spectrometer, X-Ray diffraction, Raman spectroscopy, Scanning electron microscopy (SEM) and Atomic force microscopy measurements (AFM). The UV-Visible result exhibits optical bandgap of Cu2O and CuO as 2.2 and 2.05 eV respectively. SEM and AFM result shows a uniform grain size distribution in Cu2O and CuO thin films with the average grain size of 45 and 40 nm respectively. The results of Current-Voltage and Kelvin probe force microscope characteristics describe the electrical responses of the Cu2O/ZnO and CuO/ZnO heterojunctions photodiodes. The obtained electrical response depicts the approximately same knee voltages with a measurable difference in the absolute value of net terminal current. More over the present study realizes the all oxide transparent photodiode with zero bias photocurrent. The presented results lay the template for fabricating and analysing the self-bias all oxide transparent photodetector.

• Applied Science and Convergence Technology
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• 제24권1호
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• pp.22-26
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• 2015

The optical properties of InP/GaP short-period superlattice (SPS) structures grown at various temperatures from $400^{\circ}C$ to $490^{\circ}C$ have been investigated by using temperature-dependent photoluminescence (PL) and emission wavelength-dependent time-resolved PL measurements. The PL peak energy for SPS samples decreases as the growth temperature increases. The decreased PL energy of ~10 meV for the sample grown at $425^{\circ}C$ compared to that for $400^{\circ}C$-grown sample is due to the CuPt-B type ordering, while the SPS samples grown at $460^{\circ}C$ and $490^{\circ}C$ exhibit the significant reduction of the PL peak energies due to the combined effects of the formation of lateral composition modulation (LCM) and CuPt-B type ordering. The SPS samples with LCM structure show the enhanced carrier lifetime due to the spatial separation of carriers. This study represents that the bandgap energy of InP/GaP SPS structures can be controlled by varying growth temperature, leading to LCM formation and CuPt-B type ordering.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.415-415
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• 2013

We have investigated the optical and electrical properties of the CIGS thin film solar cells by the electroreflectance (ER), photoreflectance (PR), photoluminescence (PL), and photocurrent (PC) spectroscopies at room temperature. The ER spectrum had two narrow signal regions and one broad signal region. We measured PL and PC to confirm the signals at low energy region (1.02~1.35 eV), so these signals are related to the CIGS thin film, and the high energy region (2.10~2.52 eV) is related to the CdS bandgap energy. The broad signal region (1.35~2.09 eV) is due to the internal electric field by the p-n junction from the comparison between PR and ER spectra, and we calculated the internal electric field by the p-n junction. In the high efficiency solar cell, the CdS signal of ER spectrum is narrower than the lower efficiency solar cells.

• 한국전기전자재료학회논문지
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• 제17권1호
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• pp.89-93
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• 2004

Piezoelectric fields built in I $n_{x}$G $a_1$$_{-x}$N/GaN (x=0.06∼0.1) quantum wells (QWs) have been estimated by comparing the transition energies, both calculated and measured by photoluminescence (PL). The calculation was numerically carried out with a rectangular QW model, where the effective bandgap considering a bowing facto, energy levels quantized for the lowest lying electrons and heavy holes (1e-lhh), and biaxial compressive strain were included except for the piezoelectric fields. The calculated values were observed to be larger (9∼15 meV) than the measured values by PL, which was considered to be caused by the piezoelectric fields built in InGaN/GaN QW interface. In addition, we observed the energy shift by measuring the EPDPL (excitation power-dependent PL), which was compared with the energy difference caused by the piezoelectric fields.

• 한국전기전자재료학회논문지
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• 제29권6호
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• pp.376-379
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• 2016

In this paper, the efficiency improvement of the heterojunction with intrinsic thin layer (HIT) solar cells is obtained by optimization process of p-type a-SiC:H as emitter. The optoelectronic of p-type a-SiC:H layers including the optical band-gap and conductivity under the methane gas content variation is conducted in detail. A significant increase in the Jsc by $1mA/cm^2$ and Voc by 30 mV are attributed to enhanced photon-absorption due to broader band-gap of p-a-SiC:H and reduced band-offsets at p-side interface, respectively of HIT solar cells.

• 한국진공학회지
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• 제15권6호
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• pp.624-629
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• 2006

Nd을 이온주입한 GaN를 이용하여 GaN와 Nd 이온 사이의 에너지 전달과정을 분석하고 Mg을 도핑 하였을 때의 효과를 보았다. Nd의 $^4F_{3/2}{\rightarrow}^4I_{9/2}$ 전이에 대하여 Photoluminescence (PL)와 PL excitation 방법을 이용하여 에너지 전달 경로에 적어도 3가지 이상의 밴드갭 내의 trap이 있음을 확인하였다. Mg이 doping된 GaN : Nd에서는 isoelectronic trap으로 생각되는 특정한 trap의 수가 증가되었음이 관측되었고 이로 인해 전기적으로 여기될 시료의 특성을 보여줄 밴드갭보다 큰 에너지를 이용한 여기 상태의 효율이 더욱 높아짐을 알 수 있었다.