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Effect of Processing Additives on Organic Photovoltaics: Recent Progress and Future Prospects
Kwon, Sooncheol,Kang, Hongkyu,Lee, Jong-Hoon,Lee, Jinho,Hong, Soonil,Kim, Heejoo,Lee, Kwanghee Wiley Blackwell (John Wiley Sons) 2017 Advanced energy materials Vol.7 No.10
<P>Due to the short diffusion length of approximately 10 nm of an exciton in bulk heterojunction (BHJ) organic solar cells (OSCs) comprising electron donors and acceptors, a formation with well phase-separated nanomorphology in BHJ films has been one of the most important issues in achieving efficient charge separation and extraction in OSCs. By adding a small amount of a high boiling point solvent or molecules to a bulk heterojunction (BHJ) solution, processing additive techniques have recently begun to offer an attractive and efficient method for controlling the nanoscale BHJ morphology of state-of-the-art OSCs with power conversion efficiencies (PCEs) exceeding approximately 11%. However, it remains unknown whether the effect of processing additives can potentially pave the way for the ongoing development of various BHJ components and the commercialization of OSCs. Here, recent progress in understanding and developing the effects of processing additives on OSCs is highlighted. This overview suggests possible guidelines for a wide range of BHJ components with respect to morphological/structural evolution. Furthermore, the rational correlations among processing additives, BHJ components, and fabrication technologies and the performance of high-performance and low-cost OSCs are discussed along with future commercialization prospects.</P>
Magnetic Couplings between V Monolayers through Transition Metals (Mo, Cr, W) in V/TM(001)/V Systems
SeungHyun Lee,SoonCheol Hong 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.6
We investigate the magnetic coupling between the V monolayers mediated through transition metals (TM) of Cr, Mo and W by using the full-potential linearized augmented plane wave (FLAPW) method based on density functional theory. The general gradient approximation (GGA) is used for the exchange-correlation potential. The investigated systems are composed of one monolayer of V on each side of six and seven layers of TMs. The magnetic couplings between the V monolayer and the nearest neighboring TM atoms are calculated to be antiferromagnetic (AFM). For six layers of Cr, Mo, and W(001) spacers, the AFM, ferromagnetic (FM), and FM couplings are calculated to be more stable by the total energy difference (TE = EFM . EAFM) of 10, .14 and .16 meV, respectively. For seven layers of Cr, Mo, and W(001) spacers, the FM, AFM, and AFM couplings between the V monolayers are calculated to be more stable by TE of .30, 25, and 13 meV, respectively.
Correlation between Structures and Magnetism in Iron
Dongkook Lee,Sooncheol Hong 한국자기학회 2007 Journal of Magnetics Vol.12 No.2
Even a pure bulk Fe has a complicated magnetic phase and its magnetism is still needed to be clarified. In this study we investigated the magnetism of bcc and fcc bulk Fe with total energy calculations as functions of atomic volume. The full-potential linearized augmented plane wave method was adopted within a generalized gradient approximation. The ground state of bulk Fe is confirmed to be of ferromagnetic (FM) bcc. For fcc structured Fe an antiferromagnetic (AFM) state is more stable compared to FM states which exist as low spin and high spin states. The stable AFM states were found to accompany a tetragonal distortion, while the FM states remained in a cubic symmetry. At an expanded lattice constant a high spin FM state was calculated to be able to be stabilized with significant enhanced magnetic moment compared to the value of the ground state, bcc FM.
Gim, Yeongrok,Kim, Daekyeom,Kyeong, Minkyu,Byun, Seunghwan,Park, Yuri,Kwon, Sooncheol,Kim, Heejoo,Hong, Sukwon,Lansac, Yves,Jang, Yun Hee The Royal Society of Chemistry 2016 Physical chemistry chemical physics Vol.18 No.22
<P>A new series of D-A-D-type small-molecule photovoltaic donors are designed and virtually screened before synthesis using time-dependent density functional theory calculations carefully validated against various polymeric and molecular donors. In this series of new design, benzodithiophene is kept as D to achieve the optimum highest-occupied molecular orbital energy level, while thienopyrroledione is initially chosen as A but later replaced by difluorinated benzodiathiazole or its selenide derivative to achieve the optimum band gap. The D-A-D core is end-capped by pyridone units which could not only enhance their self-assembly via hydrogen bonds but also play a role as an acceptor (A') to form an extended A'-D-A-D-A' small-molecule donor.</P>
Kang, Hongkyu,Lee, Jinho,Jung, Suhyun,Yu, Kilho,Kwon, Sooncheol,Hong, Soonil,Kee, Seyoung,Lee, Seongyu,Kim, Dongwon,Lee, Kwanghee The Royal Society of Chemistry 2013 Nanoscale Vol.5 No.23
<P>Vertically self-assembled bilayers with an interfacial bottom layer and a photoactive top layer are demonstrated via a single coating step of a blend composed of an amine-containing nonconjugated polyelectrolyte (NPE) and an organic electron donor-acceptor bulk heterojunction composite. The self-assembled NPE layer reduces the work function of an indium tin oxide (ITO) cathode, which leads to efficient inverted organic solar cells without any additional interface engineering of the ITO.</P>
Jung, In Hwan,Yu, Jinyoung,Jeong, Eunjae,Kim, Jinseck,Kwon, Sooncheol,Kong, Hoyoul,Lee, Kwanghee,Woo, Han Young,Shim, Hong-Ku WILEY-VCH Verlag 2010 Chemistry Vol.16 No.12
<P>We have synthesized four types of cyclopentadithiophene (CDT)-based low-bandgap copolymers, poly[{4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl}-alt-(2,2′-bithiazole-5,5′-diyl)] (PehCDT-BT), poly[(4,4-dioctyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl)-alt-(2,2′-bithiazole-5,5′-diyl)] (PocCDT-BT), poly[{4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl}-alt-{2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole-5,5′-diyl}] (PehCDT-TZ), and poly[(4,4-dioctyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl)-alt-{2,5-di(thiophen-2-yl)thiazolo[5,4-d]thiazole-5,5′-diyl}] (PocCDT-TZ), for use in photovoltaic applications. The intramolecular charge-transfer interaction between the electron-sufficient CDT unit and electron-deficient bithiazole (BT) or thiazolothiazole (TZ) units in the polymeric backbone induced a low bandgap and broad absorption that covered 300 nm to 700–800 nm. The optical bandgap was measured to be around 1.9 eV for PehCDT-BT and PocCDT-BT, and around 1.8 eV for PehCDT-TZ and PocCDT-TZ. Gel permeation chromatography showed that number-average molecular weights ranged from 8000 to 14 000 g mol<SUP>−1</SUP>. Field-effect mobility measurements showed hole mobility of 10<SUP>−6</SUP>–10<SUP>−4</SUP> cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> for the copolymers. The film morphology of the bulk heterojunction mixtures with [6,6]phenyl-C<SUB>61</SUB>-butyric acid methyl ester (PCBM) was also examined by atomic force microscopy before and after heat treatment. When the polymers were blended with PCBM, PehCDT-TZ exhibited the best performance with an open circuit voltage of 0.69 V, short-circuit current of 7.14 mA cm<SUP>−2</SUP>, and power conversion efficiency of 2.23 % under air mass (AM) 1.5 global (1.5 G) illumination conditions (100 mW cm<SUP>−2</SUP>).</P> <B>Graphic Abstract</B> <P>Mind the bandgap: Four types of cyclopentadithiophene (CDT)-based low-bandgap copolymers with two thiazole derivatives based on thiazolothiazole (TZ) and bithiazole (BT) structures have been synthesized (see picture for examples). The internal charge-transfer interaction between the electron-sufficient CDT unit and electron-deficient TZ or BT units in the polymeric backbone induces a low bandgap. <img src='wiley_img_2010/09476539-2010-16-12-CHEM200903064-content.gif' alt='wiley_img_2010/09476539-2010-16-12-CHEM200903064-content'> </P>
Cesarean section and risk factors: Secular tends in South Korea, 2006-2015
( Nayoung Bae ),( Hyejin Choi ),( Geumjoon Cho ),( Kyumin Lee ),( Sungwon Han ),( Kihoon Ahn ),( Sooncheol Hong ),( Haijoong Kim ),( Minjeong Oh ) 대한산부인과학회 2018 대한산부인과학회 학술대회 Vol.104 No.-
Objective: The aim of the study is to investigate the recent trend in the rate of cesarean section (CS) in South Korea from 2006 to 2015 and identify risk factors in association with these changes. Methods: Using the National Health Insurance Corporation data, we included every women who had delivery from 2006 to 2015. We investigated (1) mode of delivery, (2) the rate of complications during pregnancy (i.e. preeclampsia and placenta previa) and (3) pre-pregnancy factors (BMI, hypertension, DM and other pre-existing medical conditions) and its trends during study period. Results: During 10 years, the rate of CS increased from 36.3% in 2006 to 40.6% in 2015 (p <0.01). The rate of CS increased in primiparous women, women with multiple pregnancy and women with preeclampsia. Otherwise, the rate of vacuum delivery and VBAC decreased during study period. The rate of women with pre-pregnancy obesity increased but the rate of women with pre-pregnancy hypertension and DM decreased. Conclusion: The rate of CS in South Korea have been increasing from 2006 to 2015. This trend may reflect changes in the rate of risk factors. Identification of causes for increasing trend of CS observed in this study will allow the clinician to monitor for these factors and possibly reduce CS.
Placental expression of D6 decoy receptor in preeclampsia
( Geumjoon Cho ),( Eunsung Lee ),( Hyemi Jin ),( Jihye Lee ),( Yeunsun Kim ),( Minjeong Oh ),( Hyunjoo Seol ),( Sooncheol Hong ),( Haijoong Kim ) 대한산부인과학회 2015 Obstetrics & Gynecology Science Vol.58 No.5
The purpose of this study was to investigate the expression of the D6 decoy receptor that can bind chemokines and target them for degradation, resulting in inhibition of inflammation in placentas from preeclamptic and normal pregnancies.The current study was carried out in 35 pregnant women (23 patients with preeclampsia and 12 healthy, normotensive pregnant women) during the third trimester of pregnancy. The expressions of D6 decoy receptor in the placenta were determined with real time reverse transcriptase polymerase chain reaction and western blotting.The mRNA and protein of D6 decoy receptor were detected in all of placentas from preeclamptic and normal pregnancies. Placental D6 decoy receptor mRNA expression was significantly lower in patients with preeclampsia than in patients with normal pregnancies. Western blot analyses revealed decreased protein expression in cases of preeclampsia.The expression of the D6 decoy receptor in preeclamptic placentas was significantly lower than in normal placentas. Further studies are needed to clarify the underlying mechanisms that link decreased expression of placental D6 decoy receptor and preeclampsia.