Showing papers by "Sukwon Hong published in 2021"

Organic cathode interfacial materials for non-fullerene organic solar cells

Abstract: Amine-containing polyelectrolytes such as polyethyleneimine (PEI) are commonly used as cathode interfacial materials (CIMs); however, they are rarely found in non-fullerene acceptor (NFA) organic solar cells due to undesirable chemical reactions between PEI and NFAs. Unveiling the nature of these chemical interactions and developing chemically stable amine-containing polyelectrolytes is inevitable for achieving highly efficient and stable NFA organic solar cells. Herein, the reaction between PEI and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN)-based NFAs was investigated using a model system. 15N-isotope labeling experiments and 2D nuclear magnetic resonance (NMR) studies revealed that the products were generated by the Michael addition reaction and existed as the keto–enol tautomers. Based on the identified undesirable reaction, we developed a series of functionalized PEIs that are compatible with INCN-based NFAs by protecting the reactive amine functional groups. Highly efficient and stable NFA organic solar cells were successfully fabricated by the use of functionalized PEIs with broad work function tunability and improved chemical stability, which led to NFA organic solar cells with high power conversion efficiency (PCE) values of over 15% and thermally stable device operation for more than 360 hours at 100 °C.

Reversibly Photoswitchable Catalysts for Olefin Metathesis Reactions

Abstract: Azobenzene-bearing photoswitchable ruthenium catalysts were developed for olefin metathesis reactions. These catalysts exhibited an on–off switching ability in ring-closing metathesis depending on ...

Photocatalytic carbocarboxylation of styrenes with CO2 for the synthesis of γ-aminobutyric esters.

Abstract: Metal-free photoredox-catalyzed carbocarboxylation of various styrenes with carbon dioxide (CO2) and amines to obtain γ-aminobutyric ester derivatives has been developed (up to 91% yield, 36 examples). The radical anion of (2,3,4,6)-3-benzyl-2,4,5,6-tetra(9H-carbazol-9-yl)benzonitrile (4CzBnBN) possessing a high reduction potential (-1.72 V vs. saturated calomel electrode (SCE)) easily reduces both electron-donating and electron-withdrawing group-substituted styrenes.

Self-Assembled Bimetallic Aluminum-Salen Catalyst for the Cyclic Carbonates Synthesis.

Abstract: Bimetallic bis-urea functionalized salen-aluminum catalysts have been developed for cyclic carbonate synthesis from epoxides and CO2. The urea moiety provides a bimetallic scaffold through hydrogen bonding, which expedites the cyclic carbonate formation reaction under mild reaction conditions. The turnover frequency (TOF) of the bis-urea salen Al catalyst is three times higher than that of a μ-oxo-bridged catalyst, and 13 times higher than that of a monomeric salen aluminum catalyst. The bimetallic reaction pathway is suggested based on urea additive studies and kinetic studies. Additionally, the X-ray crystal structure of a bis-urea salen Ni complex supports the self-assembly of the bis-urea salen metal complex through hydrogen bonding.