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Chen, J-C, Chen P-Y, Chen H-Y, Chen K-H.  2018.  Analysis and characterization of an atropisomeric ionomer containing quaternary ammonium groups. Polymer. 141:143-153. AbstractWebsite

Polyethersulfone ionomers containing quaternary ammoniums were prepared for the applications on alkaline anion exchange membrane (AAEM) fuel cells. The ionomers were synthesized from 2,2′-dimethyl-4,4′-biphenyldiol and bis(4-chlorophenyl) sulfone via nucleophilic substitution followed by bromination, quaternization and anion exchange reaction. The biphenyl structure in polymer main chain exhibited atropisomerism after bromination, leading to the anisochronous signals of geminal protons on bromomethyl groups in 1H NMR spectra. Model compounds were synthesized to confirm the atropisomerism by EI mass and 1H NMR spectra. The resonance peaks from five possible repeating units of brominated polyethersulfones in the 1H NMR spectra were identified and discussed in detail. The rotational barriers of biphenyl structures containing brominated methyl groups at 2 and 2′ positions were calculated by density functional theory. The properties of these polyethersulfone anion exchange membranes (AEMs) were characterized. Their IECs ranged from 0.81 to 1.75 mequiv/g. The corresponding water uptakes and dimensional changes were in the ranges of 19–42% and 12–38%, respectively. The tensile strength of an AEM (1.75MQAPES-OH) with an IEC of 1.75 mequiv/g remained 17 MPa even though the water uptake was 42%. The hydroxide conductivity of 1.75MQAPES-OH could reach 51.4 mS/cm at 98%RH and 80 °C. After alkaline stability test for 168 h, the AEMs degraded slightly in terms of their IECs and hydroxide conductivity.

Li, CL, Huang BR, Chattopadhyay* S, Chen KH, Chen LC.  2004.  Amorphous boron carbon nitride as a pH sensor. Appl. Phys. Lett.. 84:2676-2678.
Chen, CW, Huang CC, Lin YY, Chen LC, Chen KH.  2005.  Affinity of Si-N and Si-C bond in the SiCN thin films - experimental and theoretical approaches. Diamond Relat. Mater.. 14:1126-1130.
Yang, J, Wang C-Y, Wang C-C, Chen K-H, Mou C-Y, Wu H-L.  2020.  Advanced nanoporous separators for stable lithium metal electrodeposition at ultra-high current densities in liquid electrolytes, 2020. Journal of Materials Chemistry A. 8(10):5095-5104.: The Royal Society of Chemistry AbstractWebsite

Lithium metal anodes form a dendritic structure after cycling which causes an internal short circuit in flammable electrolytes and results in battery fires. Today's separators are insufficient for suppressing the formation of lithium dendrites. Herein, we report on the use of mesoporous silica thin films (MSTFs) with perpendicular nanochannels (pore size ∼5 nm) stacking on an anodic aluminum oxide (AAO) membrane as the MSTF⊥AAO separator for advancing Li metal batteries. The nanoporous MSTF⊥AAO separator with novel inorganic structures shows ultra-long term stability of Li plating/stripping in Li–Li cells at an ultra-high current density and capacity (10 mA cm−2 and 5 mA h cm−2). A significant improvement over the state-of-the-art separator is evaluated based on three performance indicators, e.g. cycle life, current density and capacity. In Li–Cu cells, the MSTF⊥AAO separator shows a coulombic efficiency of >99.9% at a current density of 10 mA cm−2 for more than 250 h of cycling. The separator gives improved rate capability in Li–LiFePO4 (LFP) batteries. The excellent performance of the MSTF⊥AAO separator is due to good wetting of electrolytes, straight nanopores with negative charges, uniform Li deposition and blocking the finest dendrite.

Cheng-YingChen, Aprillia BS, Wei-ChaoChen, Teng Y-C, Chiu C-Y, Chen R-S, Hwang J-S, Chen K-H, Chen L-C.  2018.  Above 10% Efficiency Earth-abundant Cu2ZnSn(S,Se)4 Solar Cells by Introducing Alkali Metal Fluoride Nanolayers as Electron-selective Contacts. Nano Energy. :-. AbstractWebsite

Abstract The present investigation mainly addresses the open circuit voltage (Voc) issue in kesterites based Cu2ZnSn(S,Se)4 solar cells by simply introducing alkali metal fluoride nanolayers (  several nm NaF, or LiF) to lower the work functions of the front İTO\} contacts without conventional hole-blocking ZnO layers. Kelvin probe measurements confirmed that the work function of the front İTO\} decreases from 4.82 to 3.39 and 3.65 eV for NaF and LiF, respectively, resulting in beneficial band alignment for electron collection and/or hole blocking on top electrodes. Moreover, a 10.4% power conversion efficiency ( 11.5% in the cell effective area) \{CZTSSe\} cell with improved Voc of up to 90 mV has been attained. This demonstration may provide a new direction of further boosting the performance of copper chalcogenide based solar cells as well.

Cheng-YingChen, Aprillia BS, Wei-ChaoChen, Teng Y-C, Chiu C-Y, Chen R-S, Hwang J-S, Chen K-H, Chen L-C.  2018.  Above 10% efficiency earth-abundant Cu2ZnSn(S,Se)4 solar cells by introducing alkali metal fluoride nanolayers as electron-selective contacts, 2018. Nano Energy. 51:597-603. AbstractWebsite

The present investigation mainly addresses the open circuit voltage (Voc) issue in kesterite based Cu2ZnSn(S,Se)4 solar cells by simply introducing alkali metal fluoride nanolayers (~ several nm NaF, or LiF) to lower the work functions of the front ITO contacts without conventional hole-blocking ZnO layers. Kelvin probe measurements confirmed that the work function of the front ITO decreases from 4.82 to 3.39 and 3.65 eV for NaF and LiF, respectively, resulting in beneficial band alignment for electron collection and/or hole blocking on top electrodes. Moreover, a 10.4% power conversion efficiency (~ 11.5% in the cell effective area) CZTSSe cell with improved Voc of up to 90 mV has been attained. This demonstration may provide a new direction of further boosting the performance of copper chalcogenide based solar cells as well.

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and T. N. Arunagiri, Zhang Y, Chyan* O, El-Bounani M, Kim MJ, Wu CT, Chen LC, Chen KH.  2005.  A 5 nm ruthenium thin film as a directly plate-able copper diffusion barrier. Appl. Phys. Lett.. 86:083104-(1-3).