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( Saripally Sudhaker Reddy ),조우섬,진성호 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
The two new compounds S1 and S2, with N-atom as linker containing phenylcarbazole and fluorenyl group as main core and SBF and SBFN end cappers were designed and synthesized for blue fluorescent organic light emitting diodes (FOLEDs). The introduction of SBF has render to achieve high thermal stability and this could suppress the intermolecular interactions. Their photophysical, thermal and electrochemical properties of the material were systematically investigated by UV-visible absorption, photoluminescence (PL), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and cyclic voltammetry (CV). The two compounds display blue emission in solution and solid state. Especially, S1 exhibit deep blue emission (441 nm) with an excellent color purity (y≤ 0.10). Solution-processed devices based on these materials exhibit high efficient and stable deep blue electro luminescence. The blue Fluorescent OLEDs were fabricated with the configuration of ITO/PEDOT:PSS/emitter/TPBI/LiF/Al. The optimized fluorescent OLEDs showed impressive device performance with maximum luminance efficiency of 3.0 cd/A, maximum power efficiency of 1.5 lm/W and maximum external quantum efficiency of 2.0% with CIE coordinate of (0.14, 0.19) at 3.1 V driving voltage.
( Saripally Sudhaker Reddy ),( Sree Vijaya Gopalan ),진성호 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0
Here, we report the synthesis of two new deep-blue fluorescent emitters, namely AFpTPI and AFmTPI based on AF as a core and TPI derivatives with different linking modes for nondoped solution-processable OLEDs. Their thermal, photophysical, electrochemical, electronic distribution and device characteristics were systematically investigated and are supported by theoretical calculations. Both of them have excellent thermal stability (~450 °C) with high glass transition temperatures (141-152 °C). AFpTPI and AFmTPI show deep-blue emission in solution with high fluorescence quantum yields. In particular, solution-processed nondoped device with AFpTPI as an emitter achieved a maximum EQE of 4.56% with CIE coordinates (0.15, 0.06) and a CE of 2.39 cd A(-1), which is exactly matching with EBU blue standard. To the best of our knowledge, this is the first report on nondoped solution-processable OLEDs with efficiency close to 5% and CIE y ≤ 0.06.
A New Benzodithiophene Based Donor-Acceptor π-Conjugated Polymer for Organic Solar Cells
Saripally Sudhaker Reddy,Um Kanta Aryal,진현정,Thavamani Gokulnath,Durga Gayathri Rajalapati,Kakaraparthi Kranthiraja,신성태,진성호 한국고분자학회 2020 Macromolecular Research Vol.28 No.2
A new benzodithiophene based donor-acceptor π-conjugated polymer (P1) is designed and explored as the photoactive donor for organic solar cells (OSCs). The synthesized donor polymer, P1 displays a wide absorption profile ranging from 300-750 nm with optical band gap of 1.61 eV and moderate ionization potential of -5.30 eV. It has good solubility in non-halogenated and halogenated organic solvents. Next, we fabricated OSCs with P1 by blending with PC71BM, the pristine polymer processed from chlorobenzene showed PCE of 2.79%. Upon addition of external additive diphenyl ether to the blend showed a dramatic improvement in PCE with maximum of 5.33%. DPE tailored the active layer morphology and showed two times higher PCE than pristine films. These results clearly indicate that the new polymer has a great potentiality for enhancing efficiency upon solvent additives, which will provide new routes for the development of new class of polymers for high-performance air-stable OSCs.
Reddy, Saripally Sudhaker,Sree, Vijaya Gopalan,Park, Ho-Yeol,Maheshwaran, Athithan,Song, Myungkwan,Jin, Sung-Ho Elsevier 2017 Dyes and pigments Vol.145 No.-
<P><B>Abstract</B></P> <P>A rational design strategy is proposed for synthesis of a new deep-blue emitter/dopant (denoted as TPA-3FA) based on triphenylamine (TPA) as the core with the addition of diethylfluorene/acridine analogues to frame a star-shaped material for solution processable high performance OLEDs. The photophysical, thermal, electrochemical, electronic, and hole transporting properties of TPA-3FA are examined. Most importantly, this rational design strategy of introducing diethylfluorene between TPA and acridine imparts high rigidity and non-planarity, which in turn completely suppress intermolecular interactions, and thus yields a strong narrow deep-blue fluorescence with a high quantum yield. Moreover, a solution processed non-doped device with TPA-3FA as an emitter exhibits excellent device performance with a maximum external quantum efficiency (EQE) of 4.43%, CIE (<I>x</I>,<I>y</I>) coordinates of (0.153, 0.045) and good device stability. The device performance was significantly improved with an EQE of 6.11% and CIE (<I>x</I>,<I>y</I>) coordinates of (0.156, 0.049) after doping into a host. The same device when processed in a halogen-free solvent exhibited an impressive EL performance (EQE: 5.72%; CIE (0.157, 0.046)).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Rationally designed and synthesized an efficient deep-blue fluorescent emitter for solution processed OLEDs. </LI> <LI> A nondoped device exhibits an excellent device performance with an EQE of 4.43% and CIE (<I>x</I>,<I>y</I>) value of (0.153,0.045). </LI> <LI> Doped device performance is dramatically improved EQE of 6.11%; CIE (<I>x</I>,<I>y</I>):(0.156, 0.049). </LI> <LI> In a halogen-free solvent-processed device is also showed EQE of over 5.7% with a small CIE <I>y</I> value. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Deded Sarip Nawawi ),( Andita Maria ),( Rizal Danang Firdaus ),( Istie Sekartining Rahayu ),( Adesna Fatrawana ),( Fadlan Pramatana ),( Pamona Silvia Sinaga ),( Widya Fatriasari ) 한국목재공학회 2023 목재공학 Vol.51 No.2
Densification is an effective method for improving the physical and mechanical properties of low-density wood. However, the set-recovery of dimensions was found to be the problem of densified wood due to low fixation during the densification process. Alkali pretreatment before densification is thought to be a modification process to improve the dimensional stability of densified wood. In this research, the wood samples used were boiled in a 1.25 N sodium hydroxide (NaOH) solution at different times, followed by densification for 5 h at 100℃. The alkali pretreatment for 1, 3, and 5 h of boiling increased the dimensional stability of densified woods and anti-swelling efficiency values were 8.52%, 63.24%, and 48.94%, respectively. The boiling of wood in NaOH solution decreased the holocellulose content, as well as lignin to a lesser degree, and a lower crystallinity index was observed. The lower hydroxyl groups and a higher proportion of lignin in treated samples seem to have contributed to the high dimensional stability detected.
Veera Murugan Arivunithi,박호열,Saripally Sudhaker Reddy,도영주,박형진,신은솔,노용영,송명관,진성호 한국고분자학회 2021 Macromolecular Research Vol.29 No.2
Although perovskite solar cells (PSCs) have achieved high power conversion efficiency (PCE) by utilizing 2,2',7,7'-tetrakis(N,N'-di-p-methoxyphenylamine)- 9,9'-Spirobifluorene (Spiro-OMeTAD) as hole transporting material (HTM), the reproducibility and stability of PSCs are still a pressing concern. Herein, we introduced a solvent processed organic-organic bilayer based on 2-(4-(7-(9,9-dimethylacridin-10(9H)- yl)-9,9-diethyl-9H-fluoren-2-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole (AFpPPI) and Spiro-OMeTAD in layer to layer as HTM in PSCs. The devices configured with AFpPPI/Spiro-OMeTAD bilayer achieved a maximum PCE of 19.9% in mesoporous-TiO2 (mp-TiO2) structure with perovskite absorber of Cs0.05Rb0.05(FAPbI3)0.76 (MAPbBr3)0.14. The properties of the bilayer structure were analyzed with steadystate photoluminescence, ultra-violet photoelectron and impedance spectroscopy. The AFpPPI/Spiro-OMeTAD improved open-circuit voltage (VOC) by lowering the quasi-Fermi energy level for holes and reducing the charge recombination, resulting in high VOC (1.14 V in the champion cell) and high fill factor (FF) that lead to high PCE. The addition of AFpPPI layer improves the quality of Spiro-OMeTAD and provides pinhole-free film. Moreover, the stability is improved in controlled temperature and humid conditions. This work affords a new approach for commercial applications of PSCs with better stability.