title: Ethynyl-linked push-pull porphyrin hetero-dimers for near-IR dye-sensitized solar cells: photovoltaic performances versus excited-state dynamics.
abstract: Ethynyl-linked porphyrin hetero-dimers substituted by a series of electron donors, namely, bis(4-methoxyphenyl)amino (BMPA), bis(4-tert-butylphenyl)amino (BTBPA) and 3,6-di-tert-butylcarbazol-9-yl (DTBC) as well as a reference dimer with a non-donor moiety (3,5-di-tert-butylphenyl, DTBP) have been synthesized to systematically investigate the influence of donor introduction on the photovoltaic performances of near-IR dye-sensitized solar cells (DSCs) with these sensitizers incorporated. Despite the expected bathochromic shift and intensification of long-wavelength absorption bands as well as elevated LUMO levels and thus increased electron injection driving forces, the substitution of diphenylamino groups (BMPA and BTBPA) with stronger electron-donating abilities gave rise to surprising mediocrity in the short-circuit photocurrent densities (J(sc)), leading to overall energy conversion efficiencies in the order BMPA (3.94%) < DTBP (4.57%) < BTBPA (4.83%) < DTBC (5.21%). A study of the in situ fluorescent behavior of these sensitizers revealed that for all the sensitizers, excited-state lifetimes were significantly shortened in the simulated DSC environment compared to those in a free solution. BMPA showed the shortest intrinsic in situ lifetime while DTBC showed the longest one. These results were correlated with the photovoltaic performances, which is required for a better understanding and further design of porphyrin array sensitizers.
authors.affiliation: State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, 100084, Beijing, PR China.
authors.forename: Yizhu
authors.initials: Y
authors.lastname: Liu
authors.forename: Hong
authors.initials: H
authors.lastname: Lin
authors.forename: Jianbao
authors.initials: J
authors.lastname: Li
authors.forename: Joanne Ting
authors.initials: JT
authors.lastname: Dy
authors.forename: Koichi
authors.initials: K
authors.lastname: Tamaki
authors.forename: Jotaro
authors.initials: J
authors.lastname: Nakazaki
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nakayama
authors.forename: Chie
authors.initials: C
authors.lastname: Nishiyama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Uchida
authors.forename: Takaya
authors.initials: T
authors.lastname: Kubo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Segawa