http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Introducing paired electric dipole layers for efficient and reproducible perovskite solar cells
Lee, Jong-Hoon,Kim, Junghwan,Kim, Geunjin,Shin, Dongguen,Jeong, Song Yi,Lee, Jinho,Hong, Soonil,Choi, Jin Woo,Lee, Chang-Lyoul,Kim, Heejoo,Yi, Yeonjin,Lee, Kwanghee The Royal Society of Chemistry 2018 ENERGY AND ENVIRONMENTAL SCIENCE Vol.11 No.7
<P>Elimination of charge trapping at defects is highly challenging for poly-crystalline organometal halide perovskites. Here, we report a new architecture for reinforcing the built-in electric field (<I>E</I>in) across the photoactive layer with a pair of strong electric dipole layers (EDLs). The paired EDLs significantly intensify the <I>E</I>in across the perovskite layer, resulting in suppressed charge trapping of photogenerated charges. As a result, our low-temperature processed P-I-N planar PeSC devices using the paired EDLs exhibit a higher power conversion efficiency (<I>η</I>max ∼ 19.4%) and a smaller device-to-device variation with a standard deviation (S.D.) of 0.70%, which far surpass those (<I>η</I>max ∼ 17.8%, S.D. ∼ 1.1%) of the devices with typical charge transport layers.</P>
Kim, Sang Yong,Kim, Yesel,Lee, Kyung Moon,Yoon, Woo Sug,Lee, Ho Seok,Lee, Jong Tae,Kim, Seung-Joo,Ahn, Yeong Hwan,Park, Ji-Yong,Lee, Tai Kyu,Lee, Soonil American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.16
<P>We report fully solution-processed fabrication of transparent conducting oxide-free counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) by combining spray-coating of single-wall carbon nanotubes (SWCNTs) and chemical reduction of chloroplatinic acid precursor to platinum nanoparticles (Pt NPs) with formic acid. The power conversion efficiency of a semitransparent DSSC with such SWCNT-based CE loaded with Pt NPs is comparable to that of a control device with a conventional CE. Quantification of Pt loading shows that network morphology of entangled SWCNTs is efficient in forming and retaining chemically reduced Pt NPs. Moreover, electron microscopy and electrochemical impedance spectroscopy results show that mainly Pt NPs, which are tens of nanometers in diameter and reside at the surface of SWCNT CEs, contribute to electrocatalytic activity for triiodide reduction, to which we attribute strong correlation between power conversion efficiency of DSSCs and time constant deduced from equivalent-circuit analysis of impedance spectra.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-16/am5019447/production/images/medium/am-2014-019447_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5019447'>ACS Electronic Supporting Info</A></P>
A novel micro-machined mesh grid for a triode-type carbon nanotube field emitter
Lee, Ki Jung,Hong, Nguyen Tuan,Jo, Minuk,Lee, Soonil,Yang, Sang Sik Institute of Pure and Applied Physics 2014 Japanese Journal of Applied Physics Vol. No.
<P>An efficient electron source is developed by using a micro-machined mesh grid having opening ratio of 67% as an extraction gate for a triode-type field emitter, the cathode of which is a film of vertically-aligned carbon nanotubes (VACNTs) that are synthesized by a hot-filament chemical-vapordeposition process. The threshold electric field defined for the cathode current of 1 mu A is about 0.27V/mu m. The cathode and the anode currents as large as 250 and 140 mu A, respectively, are obtained at the electric-field strength of 0.44V/mu m. The electron transparency that corresponds to the ratio of the anode current and the cathode current is approximately 60% for anode currents larger than about 2 mu A regardless of anode-bias voltage. (C) 2014 The Japan Society of Applied Physics</P>
Simple fabrication of micro time-of-flight mass spectrometer using a carbon nanotube ionizer
Lee, Ki Jung,Hong, Nguyen Tuan,Lee, Soonil,You, Dong-Wook,Jung, Kwang-Woo,Yang, Sang Sik Elsevier 2017 Sensors and actuators. B, Chemical Vol.243 No.-
<P><B>Abstract</B></P> <P>This paper demonstrates a time-of-flight mass spectrometer (TOFMS) fabricated using simple micro electromechanical system technologies. It consists of two components: a triode-type field emitter for electron-impact ionization and ion separator with a repeller, an acceleration electrode, and a flight tube. As a cold-cathode, the field emitter with carbon nanotube is a promising electron source and offers several advantages over conventional thermionic electron sources, such as compact size, low power consumption because of the absence of heating elements, excellent durability, and high electron emission density. Micromachined TOFMS successfully detects signals of Ar and CH<SUB>3</SUB>I. This is practically proved with preliminary experiments on ionization and mass spectrum tests with Ar and CH<SUB>3</SUB>I, ions, including finite element modeling and theoretical analysis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A micromachined TOFMS with CNT-based triode-type field emitter is proposed. </LI> <LI> Simple and easy fabrication techniques are adopted such as silicon wet etching and metal deposition via shadow mask. </LI> <LI> A finite element simulation is carried out. </LI> <LI> The effects of the shape of the repelling pulse signal and initial space distribution of ion are evaluated. </LI> </UL> </P>
Soonil Kwon,Eunjung Lee,Hojin Ju,Hyo-Jeong Ahn,So-Ryoung Lee,Eue-Keun Choi,Jangwon Suh,Seil Oh,Wonjong Rhee 대한심장학회 2023 Korean Circulation Journal Vol.53 No.10
Background and Objectives: There is limited evidence regarding machine-learning prediction for the recurrence of atrial fibrillation (AF) after electrical cardioversion (ECV). This study aimed to predict the recurrence of AF after ECV using machine learning of clinical features and electrocardiograms (ECGs) in persistent AF patients. Methods: We analyzed patients who underwent successful ECV for persistent AF. Machine learning was designed to predict patients with 1-month recurrence. Individual 12-lead ECGs were collected before and after ECV. Various clinical features were collected and trained the extreme gradient boost (XGBoost)-based model. Ten-fold cross-validation was used to evaluate the performance of the model. The performance was compared to the C-statistics of the selected clinical features. Results: Among 718 patients (mean age 63.5±9.3 years, men 78.8%), AF recurred in 435 (60.6%) patients after 1 month. With the XGBoost-based model, the areas under the receiver operating characteristic curves (AUROCs) were 0.57, 0.60, and 0.63 if the model was trained by clinical features, ECGs, and both (the final model), respectively. For the final model, the sensitivity, specificity, and F1-score were 84.7%, 28.2%, and 0.73, respectively. Although the AF duration showed the best predictive performance (AUROC, 0.58) among the clinical features, it was significantly lower than that of the final machine-learning model (p<0.001). Additional training of extended monitoring data of 15-minute single-lead ECG and photoplethysmography in available patients (n=261) did not significantly improve the model’s performance. Conclusions: Machine learning showed modest performance in predicting AF recurrence after ECV in persistent AF patients, warranting further validation studies.
Lee, Jinho,Kang, Hongkyu,Kee, Seyoung,Lee, Seoung Ho,Jeong, Song Yi,Kim, Geunjin,Kim, Junghwan,Hong, Soonil,Back, Hyungcheol,Lee, Kwanghee American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.9
<P>Recently, the most efficient tandem polymer solar cells (PSCs) have used poly(3,4-ethylene-dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as a p-type component of recombination layer (RL). However, its undesirable acidic nature, originating from insulating PSS, of PEDOT:PSS drastically reduces the lifetime of PSCs. Here, we demonstrate the efficient and stable tandem PSCs by introducing acid-free self-doped conducting polymer (SCP), combined with zinc oxide nanoparticles (ZnO NPs), as RL for PEDOT:PSS-free tandem PSCs. Moreover, we introduce an innovative and versatile nanocomposite system containing photoactive and p-type conjugated polyelectrolyte (p-CPE) into the tandem fabrication of an ideal self-organized recombination layer. In our new RL, highly conductive SCP facilitates charge transport and recombination process, and p-CPE helps to achieve nearly loss-free charge collection by increasing effective work function of indium tin oxide (ITO) and SCP. Because of the synergistic effect of extremely low electrical resistance, ohmic contact, and pH neutrality, tandem devices with our novel RL performed well, exhibiting a high power conversion efficiency of 10.2% and a prolonged lifetime. These findings provide a new insight for strategic design of RLs using SCPs to achieve efficient and stable tandem PSCs and enable us to review and extend the usefulness of SCPs in various electronics research fields.</P>
Lee, Sang Tae,Kim, Min Ji,Lee, Gil-Geun,Kim, Sung Gyoo,Lee, Soonil,Seo, Won-Seon,Lim, Young Soo Elsevier 2017 Current Applied Physics Vol.17 No.5
<P>The effects of Sn-deficiency on the thermoelectric properties of polycrystalline Sni(1-x)Se (x = 0, 0.01, 0.02, and 0.04) compounds were investigated. The Sn-deficiency caused the formation of the SnSe2 secondary phase in the compounds, and the charge and thermal transport properties were affected significantly by the secondary phase. Although the Sn-deficient compounds exhibited higher thermal conductivities than stoichiometric compound due to its high thermal conductivity of SnSe2, significantly improved power factors led to the enhancement of ZT. The highest ZT of 0.61 at 848 K was achieved in Sn0.98Se compound, and detailed effects of SnSe2 on the enhancement were discussed. (C) 2017 Elsevier B.V. All rights reserved.</P>