Development of type-I/type-II hybrid dye sensitizer with both pyridyl group and catechol unit as anchoring group for type-I/type-II dye-sensitized solar cell

A type-I/type-II hybrid dye sensitizer with a pyridyl group and a catechol unit as the anchoring group has been developed and its photovoltaic performance in dye-sensitized solar cells (DSSCs) is investigated. The sensitizer has the ability to adsorb on a TiO₂ electrode through both the coordination bond at Lewis acid sites and the bidentate binuclear bridging linkage at Brønsted acid sites on the TiO₂ surface, which makes it possible to inject an electron into the conduction band of the TiO₂ electrode by the intramolecular charge-transfer (ICT) excitation (type-I pathway) and by the photoexcitation of the dye-to-TiO₂ charge transfer (DTCT) band (type-II pathway). It was found that the type-I/type-II hybrid dye sensitizer adsorbed on TiO₂ film exhibits a broad photoabsorption band originating from ICT and DTCT characteristics. Here we reveal the photophysical and electrochemical properties of the type-I/type-II hybrid dye sensitizer bearing a pyridyl group and a catechol unit, along with its adsorption modes onto TiO₂ film, and its photovoltaic performance in type-I/type-II DSSC, based on optical (photoabsorption and fluorescence spectroscopy) and electrochemical measurements (cyclic voltammetry), density functional theory (DFT) calculation, FT-IR spectroscopy of the dyes adsorbed on TiO₂ film, photocurrent-voltage (I-V) curves, incident photon-to-current conversion efficiency (IPCE) spectra, and electrochemical impedance spectroscopy (EIS) for DSSC.

Synthesis, optical and electrochemical properties, and photovoltaic performance of a panchromatic and near-infrared (D)2–π–A type BODIPY dye with pyridyl group or cyanoacrylic acid

(D)₂–π–A type BODIPY dyes bearing a pyridyl group or cyanoacrylic acid group and two diphenylamine–thienylcarbazole moieties which possess near-infrared adsorption ability as well as panchromatic adsorption ability, have been developed.

Impact of the molecular structure and adsorption mode of D-π-A dye sensitizers with a pyridyl group in dye-sensitized solar cells on the adsorption equilibrium constant for dye-adsorption on TiO2 surface

D-π-A dyes NI-4 bearing a pyridyl group, YNI-1 bearing two pyridyl groups and YNI-2 bearing two thienylpyridyl groups as the anchoring group on the TiO₂ surface have been developed as dye sensitizers for dye-sensitized solar cells (DSSCs), where NI-4 and YNI-2 can adsorb onto the TiO₂ electrode through the formation of the coordinate bond between the pyridyl group of the dye and the Lewis acid site (exposed Tiⁿ⁺ cations) on the TiO₂ surface, but YNI-1 is predominantly adsorbed on the TiO₂ electrode through the formation of the hydrogen bond between the pyridyl group of the dye and the Brønsted acid sites (surface-bound hydroxyl groups, Ti-OH) on the TiO₂ surface. The difference in the dye-adsorption mode among the three dyes on the TiO₂ surface has been investigated from the adsorption equilibrium constant (K_ad) based on the Langmuir adsorption isotherms. It was found that the K_ad values of YNI-1 and YNI-2 are higher than that of NI-4, and more interestingly, the K_ad value of YNI-2 is higher than that of YNI-1. This work demonstrates that that for the D-π-A dye sensitizers with the pyridyl group as the anchoring group to the TiO₂ surface the number of pyridyl groups and the dye-adsorption mode on the TiO₂ electrode as well as the molecular structure of the dye sensitizer affect the K_ad value for the adsorption of the dye to the TiO₂ electrode, that is, resulting in a difference in the K_ad value among the D-π-A dye sensitizers NI-4, YNI-1 and YNI-2.

Color tuning of alternating conjugated polymers composed of pentaazaphenalene by modulating their unique electronic structures involving isolated-LUMOs

Pentaazaphenalene-containing polymers with unique conjugated systems were synthesized. Various colors can be observed from the polymer solutions.

N-Heterotriangulene chromophores with 4-pyridyl anchors for dye-sensitized solar cells

A series of N-heterotriangulenes decorated with 4-pyridyl anchors were synthesized and their performance in n-type TiO₂- and ZnO-based dye-sensitized solar cells investigated.

Efficient dye-sensitized solar cells using mesoporous submicrometer TiO2 beads

Co-sensitized photoelectrodes using mesoporous submicrometer TiO₂ beads as “building blocks” can improve light absorption over a broad wavelength region.