Imperial College London


Faculty of Natural SciencesDepartment of Chemistry

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Molecular Sciences Research HubWhite City Campus





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12 results found

Park B, Kang H, Ha YH, Kim J, Lee J, Yu K, Kwon S, Jang S, Kim S, Jeong S, Hong S, Byun S, Kwon S, Kim Y, Lee Ket al., 2021, Direct observation of confinement effects of semiconducting polymers in polymer blend electronic systems, Advanced Science, Vol: 8, Pages: 1-10, ISSN: 2198-3844

The advent of special types of polymeric semiconductors, known as “polymer blends,” presents new opportunities for the development of next-generation electronics based on these semiconductors' versatile functionalities in device applications. Although these polymer blends contain semiconducting polymers (SPs) mixed with a considerably high content of insulating polymers, few of these blends unexpectedly yield much higher charge carrier mobilities than those of pure SPs. However, the origin of such an enhancement has remained unclear owing to a lack of cases exhibiting definite improvements in charge carrier mobility, and the limited knowledge concerning the underlying mechanism thereof. In this study, the morphological changes and internal nanostructures of polymer blends based on various SP types with different intermolecular interactions in an insulating polystyrene matrix are investigated. Through this investigation, the physical confinement of donor–acceptor type SP chains in a continuous nanoscale network structure surrounded by polystyrenes is shown to induce structural ordering with more straight edge-on stacked SP chains. Hereby, high-performance and transparent organic field-effect transistors with a hole mobility of ≈5.4 cm2 V–1 s–1 and an average transmittance exceeding 72% in the visible range are achieved.

Journal article

Park S, Jeong S, Kang C, Hong Set al., 2021, Synthesis of Conjugated Copolymer Containing Spirobifluorene Skeleton by Acyclic Diene Metathesis Polymerization for Polymer Light‐Emitting Diode Applications, Bulletin of the Korean Chemical Society, ISSN: 1229-5949

Journal article

Jeong S, Kim S, Kang H, Lee Ket al., 2020, Energy‐harvesting blue color filters for organic light‐emitting diodes, Advanced Optical Materials, Vol: 8, Pages: 1-5, ISSN: 2195-1071

Color filters are essential components to realize next-generation applications based on organic light-emitting diodes (OLEDs), such as flexible displays and multipurpose lighting. Although the most widely used color filters that include dyes and pigments have advantageous features, such as their simplicity and color purity, the energy wasted by these color filters does not meet the needs for a green and sustainable future. This paper presents a fullerene-free organic solar cell (OSC) color filter that is not only a highly effective blue color filter, owing to its ability to absorb green and red light, but also functions as an energy-harvesting device. OLED-OSC tandem devices with the two distinct functions of OLED and OSC within one device are successfully demonstrated. The OSC of the tandem device generates electrical energy with a power conversion efficiency of 6.83%. The OLED of the tandem device emits blue light with a maximum luminance of 1400 cd m−2, and the International Commission on Illumination (CIE) chromaticity is dramatically tunable from (0.34, 0.36) to (0.14, 0.17).

Journal article

Jeong S, Park B, Hong S, Kim S, Kim J, Kwon S, Lee J-H, Lee MS, Park JC, Kang H, Lee Ket al., 2020, Large-Area Nonfullerene Organic Solar Cell Modules Fabricated by a Temperature-Independent Printing Method, ACS Applied Materials & Interfaces, Vol: 12, Pages: 41877-41885, ISSN: 1944-8244

Journal article

Lee J, Cha H, Yao H, Hou J, Suh Y-H, Jeong S, Lee K, Durrant JRet al., 2020, Toward Visibly Transparent Organic Photovoltaic Cells Based on a Near-Infrared Harvesting Bulk Heterojunction Blend, ACS APPLIED MATERIALS & INTERFACES, Vol: 12, Pages: 32764-32770, ISSN: 1944-8244

Journal article

Kim S, Lee E, Lee Y, Kim J, Park B, Jang S-Y, Jeong S, Oh J, Lee MS, Kang H, Lee Ket al., 2020, Interface Engineering for Fabricating Semitransparent and Flexible Window-Film-Type Organic Solar Cells, ACS Applied Materials & Interfaces, Vol: 12, Pages: 26232-26238, ISSN: 1944-8244

Journal article

Jeong S, Jung S, Kang H, Choi S-B, Hong S, Lee J, Yu K, Kim N, Kee S, Lee D-S, Lee Ket al., 2019, Controlling the chromaticity of white organic light-emitting diodes using a microcavity architecture, Advanced Optical Materials, Vol: 8, Pages: 1-7, ISSN: 2195-1071

The tailoring of the chromaticity of white organic light-emitting diodes (WOLEDs) has presented a significant challenge in their application in smart lighting sources to improve the quality of life and human performance. Here, a new microcavity WOLED (M-WOLED) structure to modulate the chromaticity of the emitted light is demonstrated by only adjusting the thickness of the white light-emitting layer. By introducing a polymer-metal hybrid electrode that functions both as a partially reflective mirror and a transparent electrode, a very simple microcavity architecture that does not require additional outer mirrors, such as distributed Bragg reflectors is developed. The resulting M-WOLEDs exhibit reddish-, greenish-, and bluish-white colors with different thicknesses of the single white light-emitting layer.

Journal article

Kee S, Kim N, Park B, Kim BS, Hong S, Lee J, Jeong S, Kim A, Jang S, Lee Ket al., 2018, Highly Deformable and See‐Through Polymer Light‐Emitting Diodes with All‐Conducting‐Polymer Electrodes, Advanced Materials, Vol: 30, Pages: 1703437-1703437, ISSN: 0935-9648

Journal article

Lee J, Kim J, Lee C-L, Kim G, Kim TK, Back H, Jung S, Yu K, Hong S, Lee S, Kim S, Jeong S, Kang H, Lee Ket al., 2017, A Printable Organic Electron Transport Layer for Low-Temperature-Processed, Hysteresis-Free, and Stable Planar Perovskite Solar Cells, Advanced Energy Materials, Vol: 7, Pages: 1-7, ISSN: 1614-6832

Despite recent breakthroughs in power conversion efficiencies (PCEs), which have resulted in PCEs exceeding 22%, perovskite solar cells (PSCs) still face serious drawbacks in terms of their printability, reliability, and stability. The most efficient PSC architecture, which is based on titanium dioxide as an electron transport layer, requires an extremely high-temperature sintering process (≈500 °C), reveals hysterical discrepancies in the device measurement, and suffers from performance degradation under light illumination. These drawbacks hamper the practical development of PSCs fabricated via a printing process on flexible plastic substrates. Herein, an innovative method to fabricate low-temperature-processed, hysteresis-free, and stable PSCs with a large area up to 1 cm2 is demonstrated using a versatile organic nanocomposite that combines an electron acceptor and a surface modifier. This nanocomposite forms an ideal, self-organized electron transport layer (ETL) via a spontaneous vertical phase separation, which leads to hysteresis-free, planar heterojunction PSCs with stabilized PCEs of over 18%. In addition, the organic nanocomposite concept is successfully applied to the printing process, resulting in a PCE of over 17% in PSCs with printed ETLs.

Journal article

Jeong S, Jung S, Kang H, Lee D, Choi S-B, Kim S, Park B, Yu K, Lee J, Lee Ket al., 2017, Role of polymeric metal nucleation inducers in fabricating large-area, flexible, and transparent electrodes for printable electronics, Advanced Functional Materials, Vol: 27, Pages: 1-8, ISSN: 1616-301X

The advent of special types of transparent electrodes, known as “ultrathin metal electrodes,” opens a new avenue for flexible and printable electronics based on their excellent optical transparency in the visible range while maintaining their intrinsic high electrical conductivity and mechanical flexibility. In this new electrode architecture, introducing metal nucleation inducers (MNIs) on flexible plastic substrates is a key concept to form high-quality ultrathin metal films (thickness ≈ 10 nm) with smooth and continuous morphology. Herein, this paper explores the role of “polymeric” MNIs in fabricating ultrathin metal films by employing various polymers with different surface energies and functional groups. Moreover, a scalable approach is demonstrated using the ionic self-assembly on typical plastic substrates, yielding large-area electrodes (21 × 29.7 cm2) with high optical transmittance (>95%), low sheet resistance (<10 Ω sq−1), and extreme mechanical flexibility. The results demonstrate that this new class of flexible and transparent electrodes enables the fabrication of efficient polymer light-emitting diodes.

Journal article

Yu K, Park B, Kim G, Kim C-H, Park S, Kim J, Jung S, Jeong S, Kwon S, Kang H, Kim J, Yoon M-H, Lee Ket al., 2016, Optically transparent semiconducting polymer nanonetwork for flexible and transparent electronics, Proceedings of the National Academy of Sciences, Vol: 113, Pages: 14261-14266, ISSN: 0027-8424

Simultaneously achieving high optical transparency and excellent charge mobility in semiconducting polymers has presented a challenge for the application of these materials in future “flexible” and “transparent” electronics (FTEs). Here, by blending only a small amount (∼15 wt %) of a diketopyrrolopyrrole-based semiconducting polymer (DPP2T) into an inert polystyrene (PS) matrix, we introduce a polymer blend system that demonstrates both high field-effect transistor (FET) mobility and excellent optical transparency that approaches 100%. We discover that in a PS matrix, DPP2T forms a web-like, continuously connected nanonetwork that spreads throughout the thin film and provides highly efficient 2D charge pathways through extended intrachain conjugation. The remarkable physical properties achieved using our approach enable us to develop prototype high-performance FTE devices, including colorless all-polymer FET arrays and fully transparent FET-integrated polymer light-emitting diodes.

Journal article

Kang H, Jung S, Jeong S, Kim G, Lee Ket al., 2015, Polymer-metal hybrid transparent electrodes for flexible electronics, Nature Communications, Vol: 6, Pages: 1-7, ISSN: 2041-1723

Despite nearly two decades of research, the absence of ideal flexible and transparent electrodes has been the largest obstacle in realizing flexible and printable electronics for future technologies. Here we report the fabrication of ‘polymer-metal hybrid electrodes’ with high-performance properties, including a bending radius <1 mm, a visible-range transmittance>95% and a sheet resistance <10 Ω sq−1. These features arise from a surface modification of the plastic substrates using an amine-containing nonconjugated polyelectrolyte, which provides ideal metal-nucleation sites with a surface-density on the atomic scale, in combination with the successive deposition of a facile anti-reflective coating using a conducting polymer. The hybrid electrodes are fully functional as universal electrodes for high-end flexible electronic applications, such as polymer solar cells that exhibit a high power conversion efficiency of 10% and polymer light-emitting diodes that can outperform those based on transparent conducting oxides.

Journal article

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