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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>
Soonil Kwon,Jin-Hyung Jung,Eue-Keun Choi,Seung-Woo Lee,Jiesuck Park,So-Ryoung Lee,Jeehoon Kang,Kyungdo Han,Kyung Woo Park,Seil Oh,Gregory Y. H. Lip 대한심장학회 2021 Korean Circulation Journal Vol.51 No.5
Background and Objectives: Antithrombotic therapy after percutaneous coronary intervention (PCI) in patients with atrial fibrillation (AF) has changed in recent years with new data from large randomized trials and updates to clinical guidelines. This study aimed to investigate the trends in periprocedural antithrombotic regimens in Korean patients with AF undergoing PCI with non-vitamin K antagonist oral anticoagulants (NOACs). Methods: Using the claims database of the Health Insurance Review and Assessment during 2013–2018, 27,594 patients with AF undergoing PCI were identified. The annual prevalence of PCI and prescriptions of each antithrombotic agent, including antiplatelet agents and oral anticoagulants, within 30 days after PCI were investigated. Results: During 2013–2018, the number of patients with AF undergoing PCI increased up to 1.3-fold (from 3,913 to 5,075 patients per year). After the introduction of NOACs, the proportion of dual antiplatelet therapy (DAPT) decreased from 71.9% to 49.8% but still occupied the largest proportion among antithrombotic regimens. Triple antithrombotic therapy (TAT) use increased from 25.4% to 46.0%, and NOAC has rapidly replaced warfarin as the oral anticoagulant of choice. TAT was preferred to DAPT for patients with CHA2DS2-VASc score ≥2. Among various factors, prior intracranial hemorrhage was the most powerful predictor of favoring DAPT use over TAT. Conclusion: Since the introduction of NOACs, the patterns of periprocedural antithrombotic regimens have changed rapidly toward more use of TAT, specifically with NOAC-based regimen. Appropriate stroke prevention with oral anticoagulants is still underutilized in patients with AF undergoing PCI in Korea.
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>
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>
A triode-type carbon nanotube ionizer for micro mass spectrometer
Lee, Ki Jung,Jo, Minuk,Hong, Nguyen Tuan,Lee, Soonil,Oh, Jun Sik,Jung, Kwang Woo,Yang, Sang Sik Institute of Pure and Applied Physics 2014 Japanese Journal of Applied Physics Vol.53 No.3
<P>This article presents an ionizer based on a triode structure for a micromachined time-of-flight mass spectrometer (TOFMS). The fabricated device has two components in one chip: a triode-type field emitter for ionization and an ion separator with acceleration electrodes. The electron emitter is an array of carbon-nanotube (CNT) pillars grown by hot-filament chemical vapor deposition (HFCVD). The anode current measured in the field-emission characteristic test of the fabricated device is high, up to 72.1 mu A. The gate current is about 5% of the anode current, which implies low electron interception. We confirmed the ionization by electron impact and obtained the mass spectrum of the air from the fabricated device using a microchannel plate (MCP). The results show that the fabricated TOFMS is feasible for cheap miniature mass spectral analyzers. (C) 2014 The Japan Society of Applied Physics</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>