Ideal conducting polymer anode for perovskite light-emitting diodes by molecular interaction decoupling

Jeong, Su-Hun,Kim, Hobeom,Park, Min-Ho,Lee, Yeongjun,Li, Nannan,Seo, Hong-Kyu,Han, Tae-Hee,Ahn, Soyeong,Heo, Jung-Min,Kim, Kwang S.,Lee, Tae-Woo Elsevier 2019 Nano energy Vol.60 No.-

<P><B>Abstract</B></P> <P>An ideal conducting polymer anode (CPA) in organic and perovskite light-emitting diodes (LEDs) requires high electrical conductivity <I>κ</I>, high work function <I>WF</I>, and prevention of exciton quenching between an anode and an overlying emitting layer. However, increasing the <I>κ</I> and <I>WF</I> at the same time has been a very challenging unsolved issue due to their trade-off relationship: previous approaches to increase the <I>WF</I> have reduced the films’ <I>κ</I> and vice versa. Therefore, delicate molecular scale control of the conducting polymer compositions are required to solve this fundamental issue. Here, we introduce an effective molecular scale control strategy to decouple the <I>WF</I> with <I>κ</I> in a CPA while maintaining blocking capability of exciton quenching. This change resulted in a high current efficiency up to 52.86 cd A<SUP>−1</SUP> (10.93% ph el<SUP>−1</SUP>) in green polycrystalline perovskite LEDs. Our results provide a significant clue to develop effective CPAs for highly-efficient organic and perovskite LEDs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ideal conducting polymer anode with high work function and conductivity for high-efficiency perovskite LED is introduced. </LI> <LI> Molecular scale control is introduced to decouple the work function with conductivity in a conducting polymer anode. </LI> <LI> We achieved a high-efficiency polycrystalline perovskite LEDs with an external quantum efficiency of 10.93%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Study of the Electric Field Screening Effect for Field Emitter Arrays

Nannan Li,Fei Yan,Shucai Pang,Lei Chen,Dazhi Jin,Wei Xiang,De Zhang,Jingyi Dai,Baoqing Zeng 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.66 No.8

Understanding the influence of the interaction of emitters on the field emission performance of a field emitter array is of great importance for the design of a multi-emitter device. In this work, a screening factor S is defined to quantify the effect of electric field screening due to the interaction of emitters in an array. A three-dimensional finite integration technique is used to study the electric field screening effect for Spindt-type field emitter arrays which have potential applications in flatscreen displays and high-power vacuum electronics. The dependences of the electric field screening on the tip-to-tip spacing, half-angle of the emitter, height of the emitter and radius of the tip’s curvature are analyzed. The effects of the variations in the size of the emitter’s geometry on the most efficient arrangement to achieve maximum emission efficiency in an array are discussed.

Tailoring Electronic and Magnetic Properties of MoS₂ Nanotubes

Li, Nannan,Lee, Geunsik,Jeong, Yoon Hee,Kim, Kwang S. American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.11

<P>We have studied the electronic and magnetic structures of MoS<SUB>2</SUB> nanotubes by using a first-principles method. Various kinds of defects such as substitution and vacancy are examined for triggering spin magnetic moments toward one-dimensional diluted magnetic semiconductors. Our results suggest that the presence of impurity states within the energy gap and its large contribution to the density of states at the Fermi level are the key factors in inducing a magnetic moment. In particular, the nanotube curvature turns out to affect the energy level of impurity states, which can be exploited for tailoring magnetic properties. Also, 3d transition metal impurities (V, Mn, Fe, and Co atoms) on a Mo site can create large magnetic moments.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-11/acs.jpcc.5b00176/production/images/medium/jp-2015-00176p_0011.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b00176'>ACS Electronic Supporting Info</A></P>

Study of the Effective Field Emitting Angle for an Individual Carbon Nanotube

Nannan Li,Zhe Wu,Jianlong Liu,Hai Zhang,Jing Guo,Baoqing Zeng 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.6

In this work, the effective field emitting angle θeff is introduced for a carbon nanotube (CNT)to relate the spatial variation of the current density along the tip’s surface to the emission current. The emission current can now be calculated by using I = 2π(1-cosθeff )r2J(0), where J(0) is theemission current density at the apex and r is the radius of curvature of the tips. Analytical resultsshow that θeff depends on the macroscopic field E0, the aspect ratio h/r and the normalized fielddistribution on the tip’s surface E(θ)/E(0). Simulation results show that E(θ)/E(0) converges withincreasing h/r and can be fitted by using a formula when h/r > 500. Finally, a fit function for θeff is obtained for h/r > 500 and E0 in the range of 1 - 25 V/µm.

Preparation and Microwave Absorption Properties of the Fe/TiO2/Al2O3 Composites

Yun Li,Haifeng Cheng,Nannan Wang,Shen Zhou,Dongjin Xie,Tingting Li 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.11

To reduce the imbalance of impedance matching between the magnetic metal nanowires and free space, Fe/TiO2 core/shell nanowire arrays with different diameters were fabricated in the templates of anodic aluminum oxide membranes by electrodeposition. The influences of the microstructure on the microwave absorption properties of the Fe/TiO2/Al2O3 composites were studied by the transmission/reflection waveguide method. It was demonstrated experimentally that both the interfacial polarization and the diameter of the Fe/TiO2 core/shell nanowires have critical effects on the microwave absorption properties. We also investigated the angle dependence of the microwave absorption properties. Due to the interfacial polarization and associated relaxation, the Fe/TiO2/Al2O3 composites exhibited optimal microwave absorption properties when microwave propagation direction was accordant with the axis of the nanowires. Finally, we managed to obtain an optimal reflection loss of below -10 dB (90% absorption) over 10.2–14.8 GHz, with a thickness of 3.0mm and the minimum value of -39.4 dB at 11.7 GHz.

Characteristics of Anaphylaxis in 907 Chinese Patients Referred to a Tertiary Allergy Center: A Retrospective Study of 1,952 Episodes

Nannan Jiang,Jia Yin,Liping Wen,Hong Li 대한천식알레르기학회 2016 Allergy, Asthma & Immunology Research Vol.8 No.4

Purpose: Comprehensive evaluation of anaphylaxis in China is currently lacking. In this study, we characterized the clinical profiles, anaphylactic triggers, and emergency treatment in pediatric and adult patients. Methods: Outpatients diagnosed with “anaphylaxis” or “severe allergic reactions” in the Department of Allergy, Peking Union Medical College Hospital from January 1, 2000 to June 30, 2014 were analyzed retrospectively. Results: A total of 1,952 episodes of anaphylaxis in 907 patients were analyzed (78% were adults and 22% were children). Foods are the most common cause (77%), followed by idiopathic etiologies (15%), medications (7%) and insects (0.6%). In food-induced anaphylaxis, 62% (13/21) of anaphylaxis in infants and young children (0-3 years of age) were triggered by milk, 59% (36/61) of anaphylaxis in children (4-9 years of age) were triggered by fruits/vegetables, while wheat was the cause of anaphylaxis in 20% (56/282) of teenagers (10-17 years of age) and 42% (429/1,016) in adults (18-50 years of age). Mugwort pollen sensitization was common in patients with anaphylaxis induced by spices, fruits/vegetables, legume/peanuts, and tree nuts/seeds, with the prevalence rates of 75%, 67%, 61%, and 51%, respectively. Thirty-six percent of drug-induced anaphylaxis was attributed to traditional Chinese Medicine. For patients receiving emergency care, only 25% of patients received epinephrine. Conclusions: The present study showed that anaphylaxis appeared to occur more often in adults than in infants and children, which were in contrast to those found in other countries. In particular, wheat allergens played a prominent role in triggering food-induced anaphylaxis, followed by fruits/vegetables. Traditional Chinese medicine was a cause of drug-induced anaphylaxis. Furthermore, exercise was the most common factor aggravating anaphylaxis. Education regarding the more aggressive use of epinephrine in the emergency setting is clearly needed.

Colorimetric and Fluorescent Recognition of Fluoride by a Binaphthol Thioureido Derivative

Li-Jun Tang,Nannan Wang,Jiaojiao Guo 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.7

A new thiourea based receptor (1) was synthesized and applied to fluoride ion recognition in acetonitrile solution. Receptor 1 displayed dual changes in absorption and fluorescence emission intensities selectively for fluoride ions. The interaction of 1 with fluoride undergoes a deprotonation process that is confirmed by 1H NMR titration.

Optical polarization in mono and bilayer MoS2

박영신,Nannan Li,Christopher C.S. Chan,Benjamin P.L. Reid,Robert A. Taylor,임현식 한국물리학회 2017 Current Applied Physics Vol.17 No.9

Optical anisotropy in monolayer- and bilayer-MoS2 was investigated by polarization resolved photoluminescence measurements. The photoluminescence of monolayer-MoS2 is found to be partially polarized at 4.2 K and maintains this polarization characteristic up to room temperature, while the photoluminescence of bilayer-MoS2 shows no obvious polarization. This polarization anisotropy is due to strain effects at the interface between the MoS2 layer and the SiO2 substrate, causing symmetry breaking of the MoS2 charge distribution. Calculations using density functional theory of the electron density distribution of the monolayer- and bilayer-MoS2 in the in-plane direction are also presented, giving support to our qualitative analysis.

Bacillus ciccensis sp. nov., isolated from maize (Zea mays L.) seeds

Liu, Yang,Li, Nannan,Eom, Mi Kyung,Schumann, Peter,Zhang, Xin,Cao, Yanhua,Ge, Yuanyuan,Xiao, Ming,Zhao, Jiuran,Cheng, Chi,Kim, Song-Gun Microbiology Society 2017 International journal of systematic and evolutiona Vol.67 No.11

Inhibition of mouse SP2/0 myeloma cell growth by the B7-H4 protein vaccine

( Nan Mu ),( Nannan Liu ),( Qiang Hao ),( Yujin Xu ),( Jialin Li ),( Weina Li ),( Shouzhen Wu ),( Cun Zhang ),( Haichuan Su ) 생화학분자생물학회(구 한국생화학분자생물학회) 2014 BMB Reports Vol.47 No.7

B7-H4 is a member of B7 family of co-inhibitory molecules and B7-H4 protein is found to be overexpressed in many human cancers and which is usually associated with poor survival. In this study, we developed a therapeutic vaccine made from a fusion protein composed of a tetanus toxoid (TT) T-helper cell epitope and human B7-H4IgV domain (TT-rhB7-H4IgV). We investigated the anti-tumor effect of the TT-rhB7-H4IgV vaccine in BALB/c mice and SP2/0 myeloma growth was significantly suppressed in mice. The TT-rhB7-H4IgV vaccine induced high-titer specific antibodies in mice. Further, the antibodies induced by TT-rhB7-H4IgV vaccine were capable of depleting SP2/0 cells through complement-dependent cytotoxicity (CDC) in vitro. On the other hand, the poor cellular immune response was irrelevant to the therapeutic efficacy. These results indicate that the recombinant TT-rhB7-H4IgV vaccine might be a useful candidate of immunotherapy for the treatment of some tumors associated with abnormal expression of B7-H4. [BMB Reports 2014; 47(7): 399-404]