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Author

Jinwoo Kim

Other affiliations: KITECH
Bio: Jinwoo Kim is an academic researcher from Pusan National University. The author has contributed to research in topics: Carbazole & Polymerization. The author has an hindex of 15, co-authored 43 publications receiving 748 citations. Previous affiliations of Jinwoo Kim include KITECH.

Papers
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TL;DR: In this paper, a new electroluminescence (EL) polymer utilizing a new backbone, poly(2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta-[def]phenanthrene)) (PCPP), with stabilized blue emission is reported.
Abstract: A new electroluminescence (EL) polymer utilizing a new backbone, poly(2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta-[def]phenanthrene)) (PCPP), with stabilized blue emission is reported. PCPP was synthesized from 4H-cyclopenta[def]phenanthrene over five steps. The photoluminescence (PL) spectra of PCPP did not show any peak in the long wavelength region even after annealing for 18 h at 150 °C in air. The OLED with the configuration of ITO/PEDOT:PSS/PCPP/Al generates EL emission with a maximum peak at 400 nm, low turn-on voltage (6.0 V), and excellent CIE coordinates (x = 0.17, y = 0.12) for the blue color without any filtering. The maximum brightness of the OLEDs using PCPP was 1500 cd/m2 at 14 V. The maximum luminescence efficiency of the polymer LEDs with PCPP was 0.70 cd/A at 180 mA/cm2. In addition to this, PCPP displays stabilized blue EL emission without any low-energy emission band in the region of 500−600 nm even after annealing for 18 h at 150 °C or operation of the device for 40 min in air.

68 citations

Journal ArticleDOI
TL;DR: A green electroluminescence polymer, CN-poly(dihexylfluorenevinylene) (CN-PDHFV), which denotes poly[(9,9-dihexyl-9H-fluorene-2,7-diyl), was synthesized by condensation polymerization utilizing the Knoevenagel reaction as discussed by the authors.
Abstract: A new green electroluminescence polymer, CN-poly(dihexylfluorenevinylene) (CN-PDHFV), which denotes poly[(9,9-dihexyl-9H-fluorene-2,7-diyl)(1-cyanoethene-1,2-diyl)(9,9-dihexyl-9H-fluorene-2,7-diyl)(2-cyaoethene-1,2-diyl)], was synthesized by condensation polymerization utilizing the Knoevenagel reaction. The resulting polymer exhibits good solubility in common organic solvents such as chloroform, THF, and ODCB. The polymer is also easily cast on a glass plate to green film. The UV-vis spectrum of the polymer exhibits characteristically a broad absorption band at 440 nm. This polymer shows photoluminescence around λ max = 535 nm (exciting wavelength 410 nm) and green electroluminescence around λ max = 530 nm. The current-voltage-luminance (I-V-L) characteristics of the polymer show a turn-on voltage of 4.8 V and a brightness of 600 cd/m 2 at 5.8 V in the Al/polymer/PEDOT/ITO device. The highest efficiency was observed to be 0.85 lm/W at 5.6 V.

68 citations

Journal ArticleDOI
TL;DR: In this paper, electroluminescence (EL) was reported in photovoltaic (PV) cells based on semiconducting polymer-fullerene composites. But the authors ascribe this peak to an "electric field-assisted exciplex" formed between the electrons in the fullerenes and the holes in the polymers, thereby resulting in radiative recombination in the composites, which is totally unexpected because of a strong photoluminecence quenching in the same materials.
Abstract: We report electroluminescence (EL) in photovoltaic (PV) cells based on semiconducting polymer-fullerene composites. By applying a forward bias to the PV cells, the devices exhibited a clear EL action with a peak around 1.5 eV. We ascribe this peak to an “electric field-assisted exciplex” formed between the electrons in the fullerenes and the holes in the polymers, thereby resulting in radiative recombination in the composites. This finding is totally unexpected because of a strong photoluminescence quenching in the same materials. Since the same devices also showed typical photovoltaic effects under illumination, our results demonstrate a dual functionality in one device; polymer photovoltaic cells and polymer light-emitting diodes.

65 citations

Journal ArticleDOI
TL;DR: In this article, the MnCe oxides based catalysts with partially reduced graphene oxide support were synthesized, and the prepared catalyst exhibited high NOx removal characteristics at low temperatures.

64 citations

Journal ArticleDOI
TL;DR: In this article, two fluoro groups were introduced on every vinylene unit of poly(p-phenylenevinylene) (PPV) and poly(2-dimethyloctylsilyl-1,4-phenylonvinylene), to give PPDFV and DMOS−PPDFV in an attempt to increase the electron affinity of the parent polymer.
Abstract: New electroluminescent polymers with fluoro groups in vinylene units, poly(p-phenylenedifluorovinylene) (PPDFV) and poly(2-dimethyloctylsilyl-p-phenylenedifluorovinylene) (DMOS−PPDFV), have been synthesized by GILCH polymerization. These polymers have been used as the electroluminescent (EL) layers in double-layer light-emitting diodes (LEDs) (ITO/PEDOT/polymer/Al). PPDFV shows photoluminescence around λmax = 580 nm (exciting wavelength, 410 nm) and yellow electroluminescence around λmax = 565 nm. DMOS−PPDFV shows PL around λmax = 495 nm and green EL around λmax = 540 nm. The current−voltage−luminance (I−V−L) characteristics of the polymers show turn-on voltages of 3.0 V approximately. Two fluoro groups were introduced on every vinylene units of poly(p-phenylenevinylene) (PPV) and poly(2-dimethyloctylsilyl-1,4-phenylenevinylene) (DMOS−PPV) to give PPDFV and DMOS−PPDFV in an attempt to increase the electron affinity of the parent polymer. It was found that the efficiency of PLED of DMOS−PPDFV was about 7 t...

60 citations


Cited by
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Journal ArticleDOI
TL;DR: School of Chemistry, Bio21 Institute, University of Melbourne, 30 Flemington Road, Victoria 3010, Australia; School of Materials Science and Engineering, Nanyang Technological University, Nastyang Avenue, Republic of Singapore 639798; Institute of Materials Research and Engineering (IMRE) and the Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602.
Abstract: A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

2,378 citations

Journal ArticleDOI
TL;DR: A comprehensive review of the literature on electron transport materials (ETMs) used to enhance the performance of organic light-emitting diodes (OLEDs) is presented in this article.
Abstract: A comprehensive review of the literature on electron transport materials (ETMs) used to enhance the performance of organic light-emitting diodes (OLEDs) is presented. The structure−property−performance relationships of many classes of ETMs, both small-molecule- and polymer-based, that have been widely used to improve OLED performance through control of charge injection, transport, and recombination are highlighted. The molecular architecture, electronic structure (electron affinity and ionization potential), thin film processing, thermal stability, morphology, and electron mobility of diverse organic ETMs are discussed and related to their effectiveness in improving OLED performance (efficiency, brightness, and drive voltage). Some issues relating to the experimental procedures for the estimation of relevant material properties such as electron affinity and electron mobility are discussed. The design of multifunctional electroluminescent polymers whereby light emission and electron- and hole-transport pro...

1,527 citations

Journal ArticleDOI
TL;DR: A comprehensive review of TADF materials is presented, with a focus on linking their optoelectronic behavior with the performance of the organic light-emitting diode (OLED) and related EL devices.
Abstract: We thank the University of St Andrews for support. EZ-C thanks the Leverhulme Trust for financial support (RPG-2016-047). and the EPSRC (EP/P010482/1) for financial support.

1,317 citations

Journal ArticleDOI
TL;DR: It is demonstrated that charge-transfer absorption and emission are shown to be related to each other and Voc is determined by the formation of these states in accordance with the assumptions of the detailed balance and quasi-equilibrium theory.
Abstract: The increasing amount of research on solution-processable, organic donor-acceptor bulk heterojunction photovoltaic systems, based on blends of conjugated polymers and fullerenes has resulted in devices with an overall power-conversion efficiency of 6%. For the best devices, absorbed photon-to-electron quantum efficiencies approaching 100% have been shown. Besides the produced current, the overall efficiency depends critically on the generated photovoltage. Therefore, understanding and optimization of the open-circuit voltage (Voc) of organic solar cells is of high importance. Here, we demonstrate that charge-transfer absorption and emission are shown to be related to each other and Voc in accordance with the assumptions of the detailed balance and quasi-equilibrium theory. We underline the importance of the weak ground-state interaction between the polymer and the fullerene and we confirm that Voc is determined by the formation of these states. Our work further suggests alternative pathways to improve Voc of donor-acceptor devices.

1,121 citations

Journal ArticleDOI
TL;DR: In this article, a general experimental method to determine the energy ECT of intermolecular charge transfer (CT) states in electron donor-acceptor (D-A) blends from ground state absorption and electrochemical measurements is proposed.
Abstract: Here, a general experimental method to determine the energy ECT of intermolecular charge-transfer (CT) states in electron donor–acceptor (D–A) blends from ground state absorption and electrochemical measurements is proposed. This CT energy is calibrated against the photon energy of maximum CT luminescence from selected D–A blends to correct for a constant Coulombic term. It is shown that ECT correlates linearly with the open-circuit voltage (Voc) of photovoltaic devices in D–A blends via eVoc = ECT − 0.5 eV. Using the CT energy, it is found that photoinduced electron transfer (PET) from the lowest singlet excited state (S1 with energy Eg) in the blend to the CT state (S1 → CT) occurs when Eg − ECT > 0.1 eV. Additionally, it is shown that subsequent charge recombination from the CT state to the lowest triplet excited state (ET) of D or A (CT → T1) can occur when ECT − ET > 0.1 eV. From these relations, it is concluded that in D–A blends optimized for photovoltaic action: i) the maximum attainable Voc is ultimately set by the optical band gap (eVoc = Eg − 0.6 eV) and ii) the singlet–triplet energy gap should be ΔEST < 0.2 eV to prevent recombination to the triplet state. These favorable conditions have not yet been met in conjugated materials and set the stage for further developments in this area.

926 citations