• Title/Summary/Keyword: sub-bandgap

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Organic-Inorganic Perovskite for Highly Efficient Tandem Solar Cells (고효율 적층형 태양전지를 위한 유무기 페로브스카이트)

  • Park, Ik Jae;Kim, Dong Hoe
    • Ceramist
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    • v.22 no.2
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    • pp.146-169
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    • 2019
  • To overcome the theoretical efficiency of single-junction solar cells (> 30 %), tandem solar cells (or multi-junction solar cells) is considered as a strong nominee because of their excellent light utilization. Organic-inorganic halide perovskite has been regarded as a promising candidate material for next-generation tandem solar cell due to not only their excellent optoelectronic properties but also their bandgap-tune-ability and low-temperature process-possibility. As a result, they have been adopted either as a wide-bandgap top cell combined with narrow-bandgap silicon or CuInxGa(1-x)Se2 bottom cells or for all-perovskite tandem solar cells using narrow- and wide-bandgap perovskites. To successfully transition perovskite materials from for single junction to tandem, substantial efforts need to focus on fabricating the high quality wide- and narrow-bandgap perovskite materials and semi-transparent electrode/recombination layer. In this paper, we present an overview of the current research and our outlook regarding perovskite-based tandem solar technology. Several key challenges discussed are: 1) a wide-bandgap perovskite for top-cell in multi-junction tandem solar cells; 2) a narrow-bandgap perovskite for bottom-cell in all-perovskite tandem solar cells, and 3) suitable semi-transparent conducting layer for efficient electrode or recombination layer in tandem solar cells.

Bandgap Control of (AlxGa1-x)2O3 Epilayers by Controlling Aqueous Precursor Mixing Ratio in Mist Chemical Vapor Deposition System (미스트화학기상증착시스템의 전구체 수용액 혼합비 조절을 통한 (AlxGa1-x)2O3 에피박막의 밴드갭 특성 제어 연구)

  • Kim, Kyoung-Ho;Shin, Yun-Ji;Jeong, Seong-Min;Bae, Si-Young
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.6
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    • pp.528-533
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    • 2019
  • We investigated the growth of $(Al_xGa_{1-x})_2O_3$ thin films on c-plane sapphire substrates that were grown by mist chemical vapor deposition (mist CVD). The precursor solution was prepared by mixing and dissolving source materials such as gallium acetylacetonate and aluminum acetylacetonate in deionized water. The [Al]/[Ga] mixing ratio (MR) of the precursor solution was adjusted in the range of 0~4.0. The Al contents of $(Al_xGa_{1-x})_2O_3$ thin films were increased from 8 to 13% with the increase of the MR of Al. As a result, the optical bandgap of the grown thin films changed from 5.18 to 5.38 eV. Therefore, it was determined that the optical bandgap of grown $(Al_xGa_{1-x})_2O_3$ thin films could be effectively engineered by controlling Al content.

Electrical Characteristics of InAlAs/InGaAs/InAlAs Pseudomorphic High Electron Mobility Transistors under Sub-Bandgap Photonic Excitation

  • Kim, H.T.;Kim, D.M.
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.3 no.3
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    • pp.145-152
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    • 2003
  • Electrical gate and drain characteristics of double heterostructure InAlAs/InGaAs pseudomorphic HEMTs have been investigated under sub-bandgap photonic excitation ($hv). Drain $(V_{DS})-,{\;}gate($V_{DS})-$, and optical power($P_{opt}$)-dependent variation of the abnormal gate leakage current and associated physical mechanisms in the PHEMTs have been characterized. Peak gate voltage ($V_{GS,P}$) and the onset voltage for the impact ionization ($V_{GS.II}$) have been extracted and empirical model for their dependence on the $V_{DS}$ and $P_{opt} have been proposed. Anomalous gate and drain current, both under dark and under sub-bandgap photonic excitation, have been modeled as a parallel connection of high performance PHEMT with a poor satellite FET as a parasitic channel. Sub-bandgap photonic characterization, as a function of the optical power with $h\nu=0.799eV$, has been comparatively combined with those under dark condition for characterizing the bell-shaped negative humps in the gate current and subthreshold drain leakage under a large drain bias.

Mechanochemically Synthesized Cu2Zn(Sn,Ge)S4 Nanocrystals and Their Application to Solar Cells (기계화학적 방법으로 합성한 Cu2Zn(Sn,Ge)S4 나노결정과 이를 이용하여 제조한 태양전지)

  • Park, Bo-In;Lee, Seung Yong;Lee, Doh-Kwon
    • Current Photovoltaic Research
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    • v.4 no.3
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    • pp.114-118
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    • 2016
  • $Cu_{1.8}Zn_{1.2}(Sn_{1-x}Ge_x)S_4$ (CZTGeS) nanocrystals were mechanochemically synthesized from elemental precursor powders without using any organic solvents and any additives. The composition of CZTGeS nanocrystals were systematically varied with different Ge mole fraction (x) from 0.1 to 0.9. The XRD, Raman spectroscopy, high-resolution TEM, and diffuse reflectance studies show that the as-synthesized CZTGeS nanocrystals exhibited consistent changes in various structural and optical properties as a function of x, such as lattice parameters, wave numbers for $A_1$ Raman vibration mode, interplanar distances (d-spacing), and optical bandgap energies. The bandgap energy of the synthesized CZTGeS nanocrystals gradually increases from 1.40 to 1.61 eV with increasing x from 0.1 to 0.9, demonstrating that Ge-doping is useful means to tune the bandgap of mechanochemically synthesized nanocrystals-based kesterite thin-film solar cells. The preliminary solar cell performance is presented with an efficiency of 3.66%.

Bandgap Engineering in CZTSSe Thin Films via Controlling S/(S+Se) Ratio

  • Vijay C. Karade;Jun Sung Jang;Kuldeep Singh, Gour;Yeonwoo Park;Hyeonwook, Park;Jin Hyeok Kim;Jae Ho Yun
    • Current Photovoltaic Research
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    • v.11 no.3
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    • pp.67-74
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    • 2023
  • The earth-abundant element-based Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cells (TFSCs) have attracted greater attention in the photovoltaic (PV) community due to their rapid development in device power conversion efficiency (PCE) >13%. In the present work, we demonstrated the fine-tuning of the bandgap in the CZTSSe TFSCs by altering the sulfur (S) to the selenium (Se) chalcogenide ratio. To achieve this, the CZTSSe absorber layers are fabricated with different S/(S+Se) ratios from 0.02 to 0.08 of their weight percentage. Further compositional, morphological, and optoelectronic properties are studied using various characterization techniques. It is observed that the change in the S/(S+Se) ratios has minimal impact on the overall Cu/(Zn+Sn) composition ratio. In contrast, the S and Se content within the CZTSSe absorber layer gets altered with a change in the S/(S+Se) ratio. It also influences the overall absorber quality and gets worse at higher S/(S+Se). Furthermore, the device performance evaluated for similar CZTSSe TFSCs showed a linear increase and decrease in the open circuit voltage (Voc) and short circuit current density (Jsc) of the device with an increasing S/(S+Se) ratio. The external quantum efficiency (EQE) measured also exhibited a linear blue shift in absorption edge, increasing the bandgap from 1.056 eV to 1.228 eV, respectively.

The Effect of Blue Light Interception and SPF Boosting of Sunscreen Prepared with Bandgap-controlled TiO2 (밴드갭이 제어된 TiO2 를 이용한 자외선 차단제의 블루라이트 차단 및 SPF 부스팅 효과)

  • Sung Eun Wang;Jung Kyung Yoon;Gui Su Chung;Sung Bong Kye;Ho Sik Rho;Dae Soo Jung
    • Journal of the Society of Cosmetic Scientists of Korea
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    • v.49 no.2
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    • pp.159-167
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    • 2023
  • Titanium dioxide (TiO2) is commonly used in sunscreen formulations to protect the skin surface and prevent the penetration of harmful ultraviolet (UV) rays by the physical scattering action of light. However, a disadvantage of using TiO2 is that it can cause white turbidity when used on skin due to its inactive mineral ingredient. In addition, when TiO2 particles are reduced to nanosize to eliminate opacity, they can increase the transmittance of visible light and reduce whitening, but may lead to serious skin problems, such as allergic inflammation. To overcome these issues, the bandgap of TiO2 was controlled by adjusting the amount of oxygen defect and nitrogen amount, resulting in color TiO2 tailored to the skin. This innovative technology can reduce the whitening phenomenon and effectively block blue light, which is known to cause skin aging by inducing active oxygen. The bandgap controlled TiO2 compounds proposed in this study are hypoallergenic, broad-spectrum, and environmentally friendly. Furthermore, these compounds have been shown to significantly enhance sun protection factor (SPF) of sunscreens, demonstrating their compatibility with blue light blocking products.

CO2 Reduction and C2H4 Production Using Nanostructured Gallium Oxide Photocatalyst (산화갈륨 나노구조 광촉매 특성을 이용한 이산화탄소 저감 및 에틸렌 생성 작용)

  • Seo, Dahee;Ryou, Heejoong;Seo, Jong Hyun;Hwang, Wan Sik
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.35 no.3
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    • pp.308-310
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    • 2022
  • Ultrawide bandgap gallium oxide (Ga2O3) semiconductors are known to have excellent photocatalytic properties due to their high redox potential. In this study, CO2 reduction is demonstrated using nanostructured Ga2O3 photocatalyst under ultraviolet (254 nm) light source conditions. After the CO2 reduction, C2H4 remained as a by-product in this work. Nanostructured Ga2O3 photocatalyst also showed an excellent endurance characteristic. Photogenerated electron-hole pairs boosted the CO2 reduction to C2H4 via nanostructured Ga2O3 photocatalyst, which is attributed to the ultrawide and almost direct bandgap characteristics of the gallium oxide semiconductor. The findings in this work could expedite the realization of CO2 reduction and a simultaneous C2H4 production using a low cost and high performance photocatalyst.

Properties of ZnO Thin Films Grown by Radio-frequency Magnetron Sputtering in terms of O2/Ar Mixture Flow Ratio (O2/Ar 혼합 유량비를 변수로 갖는 라디오파 마그네트론 스퍼터링으로 성장된 ZnO 박막의 특성)

  • Cho, Shin-Ho
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.20 no.11
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    • pp.932-938
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    • 2007
  • The structural, optical, and electrical properties of ZnO thin films grown on glass by radio-frequency (rf) magnetron sputtering were investigated. The mixture flow ratio of $O_2$ to Ar, which was operated with sputtering gas, was chosen as a parameter for growing high-qualify ZnO thin films. The structural properties and surface morphologies of the thin films were characterized by the X-ray diffraction and the atomic force microscope, respectively. As for the optical properties of the films, the optical absorbance was measured in the wavelength range of 300-1100 nm by using UV-VIS spectrophotometer. The optical transmittance, absorption coefficient, and optical bandgap energy of ZnO thin films were calculated from the measured data. The crystallinity of the films was improved and the bandgap energy was increased from 3.08 eV to 3.23 eV as the oxygen flow ratio was increased from 0 % to 50 %. Furthermore, The ultraviolet and violet luminescences were observed by using photoluminescence spectroscopy. The hall mobility was decreased with the increase of oxygen flow ratio.

Rhodomine B dye removal and inhibitory effect on B. subtilis and S. aureus by WOx nanoparticles

  • Ying, Yuet Lee;Pung, Swee Yong;Ong, Ming Thong;Pung, Yuh Fen
    • Journal of Industrial and Engineering Chemistry
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    • v.67
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    • pp.437-447
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    • 2018
  • Visible-light-driven wide bandgap semiconductor photocatalysts were commonly developed via doping or coupling with another narrow bandgap metal oxide. However, these approaches required extra processing. The aim of study was to evaluate the photocatalytic performance of narrow bandgap $WO_x$ nanoparticles. A mixture of $WO_2$ and $WO_3$ nanoparticles were synthesized using solution precipitation technique. The photodegradation of RhB by these nanoparticles more effective in UV light than in visible light. In antibacterial susceptibility assay, $WO_x$ nanoparticles demonstrated good antibacterial against Gram-positive bacteria. The cell wall of bacterial was the main determinant in antibacterial effect other than $W^{4+}/W^{6+}$ ions and ROS.