title: Tailoring of energy levels in D-π-A organic dyes via fluorination of acceptor units for efficient dye-sensitized solar cells.
abstract: A molecular design is presented for tailoring the energy levels in D-π-A organic dyes through fluorination of their acceptor units, which is aimed at achieving efficient dye-sensitized solar cells (DSSCs). This is achieved by exploiting the chemical structure of common D-π-A organic dyes and incorporating one or two fluorine atoms at the ortho-positions of the cyanoacetic acid as additional acceptor units. As the number of incorporated fluorine atoms increases, the LUMO energy level of the organic dye is gradually lowered due to the electron-withdrawing effect of fluorine, which ultimately results in a gradual reduction of the HOMO-LUMO energy gap and an improvement in the spectral response. Systematic investigation of the effects of incorporating fluorine on the photovoltaic properties of DSSCs reveals an upshift in the conduction-band potential of the TiO2 electrode during impedance analysis; however, the incorporation of fluorine also results in an increased electron recombination rate, leading to a decrease in the open-circuit voltage (Voc). Despite this limitation, the conversion efficiency is gradually enhanced as the number of incorporated fluorine atoms is increased, which is attributed to the highly improved spectral response and photocurrent.
authors.affiliation: 1] Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Korea [2] Department of Chemistry, Sogang University, Seoul, 121-742, Korea.
authors.forename: Min-Woo
authors.initials: MW
authors.lastname: Lee
authors.affiliation: Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Korea.
authors.forename: Jae-Yup
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Korea.
authors.forename: Hae Jung
authors.initials: HJ
authors.lastname: Son
authors.affiliation: 1] Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Korea [2] Green School, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 136-701, Korea.
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Kim
authors.affiliation: 1] Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Korea [2] Green School, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 136-701, Korea.
authors.forename: BongSoo
authors.initials: B
authors.lastname: Kim
authors.affiliation: 1] Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Korea [2] Green School, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 136-701, Korea.
authors.forename: Honggon
authors.initials: H
authors.lastname: Kim
authors.affiliation: Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Korea.
authors.forename: Doh-Kwon
authors.initials: DK
authors.lastname: Lee
authors.affiliation: Department Chemistry and Nano Science, Ewha Womans University, Seoul, 120-750, Korea.
authors.forename: Kyungkon
authors.initials: K
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Sogang University, Seoul, 121-742, Korea.
authors.forename: Duck-Hyung
authors.initials: DH
authors.lastname: Lee
authors.affiliation: 1] Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul, 136-791, Korea [2] Green School, Korea University, 145, Anam-ro, Seongbuk-gu, Seoul 136-701, Korea.
authors.forename: Min Jae
authors.initials: MJ
authors.lastname: Ko