title: High Color-Purity Green, Orange, and Red Light-Emitting Diodes Based on Chemically Functionalized Graphene Quantum Dots.
abstract: Chemically derived graphene quantum dots (GQDs) to date have showed very broad emission linewidth due to many kinds of chemical bondings with different energy levels, which significantly degrades the color purity and color tunability. Here, we show that use of aniline derivatives to chemically functionalize GQDs generates new extrinsic energy levels that lead to photoluminescence of very narrow linewidths. We use transient absorption and time-resolved photoluminescence spectroscopies to study the electronic structures and related electronic transitions of our GQDs, which reveals that their underlying carrier dynamics is strongly related to the chemical properties of aniline derivatives. Using these functionalized GQDs as lumophores, we fabricate light-emitting didoes (LEDs) that exhibit green, orange, and red electroluminescence that has high color purity. The maximum current efficiency of 3.47 cd A(-1) and external quantum efficiency of 1.28% are recorded with our LEDs; these are the highest values ever reported for LEDs based on carbon-nanoparticle phosphors. This functionalization of GQDs with aniline derivatives represents a new method to fabricate LEDs that produce natural color.
authors.affiliation: Department of Chemical and Biological Engineering, Sookmyung Women's University, 100 Cheongpa-ro 47-gil, Yongsan-gu, Seoul 04310, Republic of Korea.
authors.forename: Woosung
authors.initials: W
authors.lastname: Kwon
authors.affiliation: Department of Materials Science &Engineering, Pohang University of Science &Technology (POSTECH), 77 Cheongam-ro, Nam-gu, Pohang 37673, Republic of Korea.
authors.forename: Young-Hoon
authors.initials: YH
authors.lastname: Kim
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16419, Republic of Korea.
authors.forename: Ji-Hee
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Chemical Engineering, Pohang University of Science &Technology (POSTECH), 77 Cheongam-ro, Nam-gu, Pohang 37673, Republic of Korea.
authors.forename: Taehyung
authors.initials: T
authors.lastname: Lee
authors.affiliation: Department of Chemical Engineering, Pohang University of Science &Technology (POSTECH), 77 Cheongam-ro, Nam-gu, Pohang 37673, Republic of Korea.
authors.forename: Sungan
authors.initials: S
authors.lastname: Do
authors.affiliation: Department of Chemical Engineering, Pohang University of Science &Technology (POSTECH), 77 Cheongam-ro, Nam-gu, Pohang 37673, Republic of Korea.
authors.forename: Yoonsang
authors.initials: Y
authors.lastname: Park
authors.affiliation: Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16419, Republic of Korea.|Department of Energy Science, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 440-746, Republic of Korea.
authors.forename: Mun Seok
authors.initials: MS
authors.lastname: Jeong
authors.affiliation: Department of Materials Science &Engineering, Pohang University of Science &Technology (POSTECH), 77 Cheongam-ro, Nam-gu, Pohang 37673, Republic of Korea.
authors.forename: Tae-Woo
authors.initials: TW
authors.lastname: Lee
authors.affiliation: Department of Chemical and Biological Engineering, Sookmyung Women's University, 100 Cheongpa-ro 47-gil, Yongsan-gu, Seoul 04310, Republic of Korea.|Department of Chemical Engineering, Pohang University of Science &Technology (POSTECH), 77 Cheongam-ro, Nam-gu, Pohang 37673, Republic of Korea.
authors.forename: Shi-Woo
authors.initials: SW
authors.lastname: Rhee