title: Co-sensitization of organic dyes for efficient dye-sensitized solar cells.
abstract: Novel cyanine dyes, in which a tetrahydroquinoline derivative is used as an electron donor and 1-butyl-5-carboxy-3, 3-dimethyl-indol-1-ium moiety is used as an electron acceptor and anchoring group, were designed and synthesized for application in dye-sensitized solar cells. The photovoltaic performance of these solar cells depends markedly on the molecular structure of the dyes in terms of the n-hexyl chains and the methoxyl unit. Retardation of charge recombination caused by the introduction of n-hexyl chains resulted in an increase in electron lifetime. As a consequence, an improvement of open-circuit photovoltage (V(oc)) was achieved. Also, the electron injection efficiencies were improved by the introduction of methoxyl moiety, which led to a higher short-circuit photocurrent density (J(sc)). The highest average efficiency of the sensitized devices (η) was 5.6% (J(sc)=13.3 mA cm(-2), V(oc)=606 mV, and fill factor FF=69.1%) under 100 mW cm(-2) (AM 1.5G) solar irradiation. All of these dyes have very high absorption extinction coefficients and strong absorption in a relatively narrow spectrum range (500-650 nm), so one of our organic dyes was explored as a sensitizer in co-sensitized solar cells in combination with the other two other existing organic dyes. Interestingly, a considerably improved photovoltaic performance of 8.2% (J(sc)=20.1 mA cm(-2), V(oc)=597 mV, and FF=68.3%) was achieved and the device showed a panchromatic response with a high incident photon-to-current conversion efficiency exceeding 85% in the range of 400-700 nm.
authors.affiliation: State Key Laboratory of Fine Chemicals, DUT-KTH Joint Education and Research Centre on Molecular Devices, Dalian University of Technology (DUT), 2 Linggong Rd., 116024 Dalian, PR China.
authors.forename: Ming
authors.initials: M
authors.lastname: Cheng
authors.forename: Xichuan
authors.initials: X
authors.lastname: Yang
authors.forename: Jiajia
authors.initials: J
authors.lastname: Li
authors.forename: Fuguo
authors.initials: F
authors.lastname: Zhang
authors.forename: Licheng
authors.initials: L
authors.lastname: Sun
mesh_terms: D002232:Carbocyanines / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D058266:Dielectric Spectroscopy; D011211:Electric Power Supplies; D012993:Solar Energy
chemical_list: D002232:Carbocyanines; D004396:Coloring Agents