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Kim, Woochul,Park, Jiyoon,Kim, Hyeonghun,Pak, Yusin,Lee, Heon,Jung, Gun Young Elsevier 2017 ELECTROCHIMICA ACTA Vol.245 No.-
<P><B>Abstract</B></P> <P>Organic-inorganic hybrid perovskite solar cells (PSCs) have reached a power conversion efficiency of 22.1% in a short period (∼7 years), which has been obtainable in silicon-based solar cells for decades. The high power conversion efficiency and simple fabrication process render perovskite solar cells as potential future power generators, after overcoming the lack of long-term stability, for which the deposition of void-free and pore-filled perovskite films on mesoporous TiO<SUB>2</SUB> layers is the key pursuit. In this research, we developed a sequential dip-spin coating method in which the perovskite solution can easily infiltrate the pores within the TiO<SUB>2</SUB> nanoparticulate layer, and the resultant film has large crystalline grains without voids between them. As a result, a higher short circuit current is achieved owing to the large interfacial area of TiO<SUB>2</SUB>/perovskite, along with enhanced power conversion efficiency, compared to the conventional spin coating method. The as-made pore-filled and void-free perovskite film avoids intrinsic moisture and air and can effectively protect the diffusion of degradation factors into the perovskite film, which is advantageous for the long-term stability of PSCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sequential dip-spin coating method is developed to coat a uniform perovskite film without voids. </LI> <LI> The dip-spin coated perovskite film increases the recombination resistance owing to complete pore-filling, enhancing the J<SUB>SC</SUB> and PCE. </LI> <LI> A void-free and pore-filled perovskite film with large grains (average 2.10μm) is achieved by the dip-spin coating. </LI> <LI> The pore-filled and void-free perovskite film fabricated via dip-spin coating prevents the diffusion. </LI> <LI> The cell fabricated via the dip-spin coating maintains 99% of their initial PCE after 35days of storage. </LI> </UL> </P>
Kim, Hyeonghun,Pak, Yusin,Jeong, Yeonggyo,Kim, Woochul,Kim, Jeongnam,Jung, Gun Young Elsevier 2018 Sensors and actuators. B Chemical Vol.262 No.-
<P><B>Abstract</B></P> <P>For monitoring H<SUB>2</SUB> concentrations in air, diverse resistive gas sensors have been demonstrated. In particular, Pd-decorated metal oxides have shown remarkable selectivity and sensing response for H<SUB>2</SUB> detection. In this work, H<SUB>2</SUB> sensing behavior of amorphous Pd layer covering ZnO nanorods (am-Pd/ZnO NRs) is investigated. This is the first report on the enhanced gas sensing performance attained by using an amorphous metal layer. The amorphous Pd layer is generated by reduction reaction with a strong reducing agent (NaBH<SUB>4</SUB>), and it covers the ZnO nanorods completely with a thickness of 2–5 nm. For comparison, crystalline Pd nanoparticles-decorated ZnO nanorods (c-Pd/ZnO NRs) are produced using a milder reducing agent like hydrazine. Comparing the c-Pd/ZnO NRs sensor and other previously reported hydrogen sensors based on the crystalline Pd and metal oxides, the am-Pd/ZnO NRs sensor exhibits a remarkable sensing response (12,400% at 2% H<SUB>2</SUB>). The enhancement is attributed to complete cover of the amorphous Pd layer on the ZnO NRs, inducing larger interfaces between the Pd and ZnO. In addition, the amorphous Pd layer prevents surface contamination of the ZnO NRs. Therefore, the am-Pd/ZnO NRs sensor maintains initial sensing performance even after 5 months.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Facile synthesis of ultrathin amorphous Pd layer (2–5 nm) on ZnO nanorods. </LI> <LI> Comparison of sensing behavior between amorphous and crystalline Pd-coated ZnO nanorods sensors. </LI> <LI> Demonstration of superior sensing response (12,400%) of amorphous Pd-coated ZnO nanorods sensors. </LI> <LI> High stability of amorphous Pd-coated ZnO nanorods sensors. </LI> </UL> </P>
Erratum to: Charge transfer in graphene/polymer interfaces for CO2 detection
Kim, Kihyeun,Son, Myungwoo,Pak, Yusin,Chee, Sang-Soo,Auxilia, Francis Malar,Lee, Byung-Kee,Lee, Sungeun,Kang, Sun Kil,Lee, Chaedeok,Lee, Jeong Soo,Kim, Ki Kang,Jang, Yun Hee,Lee, Byoung Hun,Jung, Gun- Springer-Verlag 2018 NANO RESEARCH Vol.11 No.7
Palladium-Decorated Hydrogen-Gas Sensors Using Periodically Aligned Graphene Nanoribbons
Pak, Yusin,Kim, Sang-Mook,Jeong, Huisu,Kang, Chang Goo,Park, Jung Su,Song, Hui,Lee, Ryeri,Myoung, NoSoung,Lee, Byoung Hun,Seo, Sunae,Kim, Jin Tae,Jung, Gun-Young American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.15
<P>Polymer residue-free graphene nanoribbons (GNRs) of 200 nm width at 1 μm pitch were periodically generated in an area of 1 cm<SUP>2</SUP> via laser interference lithography using a chromium interlayer prior to photoresist coating. High-quality GNRs were evidenced by atomic force microscopy, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy measurements. Palladium nanoparticles were then deposited on the GNRs as catalysts for sensing hydrogen gases, and the GNR array was utilized as an electrically conductive path with less electrical noise. The palladium-decorated GNR array exhibited a rectangular sensing curve with unprecedented rapid response and recovery properties: 90% response within 60 s at 1000 ppm and 80% recovery within 90 s in nitrogen ambient. In addition, reliable and repeatable sensing behaviors were revealed when the array was exposed to various gas concentrations even at 30 ppm.</P><P>A polymer residue-free graphene nanoribbon (GNR) array with a 200 nm line width at 1 μm pitch is fabricated via laser interference lithography by depositing a chromium interlayer prior to photoresist coating. The palladium-decorated GNR-array hydrogen-gas sensor exhibits reliable and repeatable behaviors as well as rapid response and recovery characteristics: 90% response within 60 s at 1000 ppm and 80% recovery within 90 s in nitrogen ambient.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-15/am503105s/production/images/medium/am-2014-03105s_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am503105s'>ACS Electronic Supporting Info</A></P>
Lee, Kwang‐,Ho,Kim, Sang‐,Mook,Jeong, Huisu,Pak, Yusin,Song, Hui,Park, Jeongpil,Lim, Keon‐,Hee,Kim, Jae‐,Hoon,Kim, Youn Sang,Ko, Heung Cho,Kwon, Il Keun,Jung, Gun‐,Young WILEY‐VCH Verlag 2013 ADVANCED MATERIALS Vol.25 No.23
<P><B>All‐solution‐processed transparent thin film transistors (TTFTs)</B> are demonstrated with silver grid source/drain electrodes, which are fabricated by printing and subsequent silver nanoparticles solution coating, which allows continuous processing without using high vacuum systems. The silver grid electrode shows a reasonable transmittance in visible range, moderate electrical conductance and mechanical strength. The TTFTs are employed to drive liquid crystal cells and demonstrate a successful switching operation.</P>