In this work, a metal-mediated assembling strategy has been used to organize a series of new assemblies based on tetrapyridylporphyrin (ZnP) on nanostructured TiO2 electrode surfaces, wherein the metal ions (M, M = Zn2+, Cd2+, Hg2+ and Mn2+) bridge the pyridyl units of ZnP and (E)-4-[(pyridin-4-ylmethylene)-amino]benzoic acid (A), resulting in a ZnP–M–A assembled mode. The assembled structures were characterized by transmission electron microscopy (TEM), computational calculations, energy-dispersive X-ray spectroscopy (EDX), IR, UV-vis absorption and fluorescence spectra. The performances of the assembly-sensitized solar cells were also measured under an irradiance of 100 mW cm−2 AM 1.5G sunlight. Photoelectrochemical results reveal a relatively large photocurrent of the ZnP–Mn–A device. Simultaneously, a large open-circuit photovoltage and a significantly improved conversion efficiency of the ZnP–Zn–A device are also observed. These findings may serve as another good testing ground for the fabrication of supramolecular solar cells in future.

We report two triarylamine-cyanoacrylic acid based push–pull dyes C252 and C253 featuring the π-conjugated linkers of 2,6-di(thiophen-2-yl)-4H-dithieno[3,2-b:2′,3′-d]pyrrole and 4H,4′H-2,2′-bidithieno[3,2-b:2′,3′-d]pyrrole, respectively. Benefitting from an improved coplanarity of the conjugated units, the C253 dye displays a red-shifted absorption peak and an enhanced maximum molar absorption coefficient in comparison with C252. However, this pattern of conjugated linker alternation is associated with an 80 mV negative shift of the ground-state oxidation potential, which dominates an almost 5 times reduced rate of hole injection from the oxidized state of C253 to the divalent tris(2,2′-bipyridine)cobalt (Co-bpy) cation in the redox electrolyte, resulting in a considerably poor net charge separation yield. On the other side, a dye-sensitized solar cell employing the C252 photosensitizer and the Co-bpy electrolyte exhibits a good power conversion efficiency of 9.5% measured under the 100 mW cm−2 simulated AM1.5 sunlight. The dissimilarity of cell photovoltage is scrutinized by evaluating the shift of the titania conduction band edge and the variation of interfacial charge recombination kinetics, the latter of which presents a clear correlation with dye coating thickness on titania derived from X-ray photoelectron spectroscopy measurements. Our work has underlined the important energetic and kinetic interplays which should be seriously considered in the further optimization of active components in dye-sensitized solar cells.

The rigidification of π-conjugated segments represents a feasible tactic towards energy-level engineering of organic D-π-A dyes in mesoscopic titania solar cells. In this work, comparions of four dyes with the di(3-hexylthiophene), dihexyldithienosilole, dihexylcyclopentadithiophene and N-hexyldithienopyrrole linkers have revealed some general influences of π-linker rigidification on the optoelectronic features of titania solar cells employing a cobalt(II/III) redox electrolyte, in terms of energetic and kinetic viewpoints. Compared to a dye with the di(3-hexylthiophene) linker, its three counterparts with rigidified dithiophene blocks present bathochromic and hyperchromic absorptions of solar photons. Transient absorption measurements have shown that the incorporation of Si-, C- and N-bridged dithiophene segments decelerates the dye regeneration kinetics. The rigidification of π-conjugated dithiophene linkers brings forth a general open-circuit photovoltage diminishment, in the range from 60 to 190 mV. Further insightful impedance analyses have disclosed that the open-circuit photovoltage reduction, due to the π-linker alternation from di(3-hexylthiophene) to N-hexyldithienopyrrole, is predominantly caused by an adverse downward displacement of the titania conduction band edge, despite a positive contribution from attenuated charge recombination at the titania/electrolyte interface.

Through elongating the end or side alkyl chains of dye molecules, we decorate anatase nanocrystals with a thicker organic assembly featuring a smaller tilt angle of the D–π-A backbone with respect to the surface normal, which retards the interfacial charge recombination and confers a higher photovoltage output on mesoscopic cobalt solar cells displaying an over 10% power conversion efficiency at the AM1.5G conditions.

The electron donor of a D-π-A dye is known for its capability to tune both the electronic trait and packing mode of dye molecules chemisorbed on titania nanocrystals of dye-sensitized solar cells (DSCs), bringing on the opportunity to impact cell performance by modulating the physicochemical characteristics at the titania/dye/electrolyte interface. In this paper, we scrutinize the influences of arylamine electron donors on the optoelectronic features of thin-film DSCs employing a tris(1,10-phenanthroline)cobalt(II/III) redox electrolyte, by use of four cyclopentadithiophene dyes (C218, C244, C245 and C246) with the respective dihexyloxy-, diphenothiazinyl- or di-tert-butylphenyl-substituted triphenylamine and N-hexyl-carbazole electron donors. Amongst these electron donors, dihexyloxy-substituted triphenylamine is found to present the strongest electron-donating capacity, endowing the corresponding C218 dye with evidently red-shifted light absorption in comparison with the other three congeners. Transient absorption measurements show that all DSCs exhibit expeditious dye regeneration, guaranteeing efficient long-distance charge separation at the titania/dye/redox couple interface. Furthermore, it is worthwhile noting that the C218 dye prompts the highest open-circuit photovoltage amongst these chromophores, which is primarily attributed to the positive effect of slow cobalt(III) interception of titania electrons, highlighting the superiority of applying dihexyloxy-substituted triphenylamine as the electron donor for a cyclopentadithiophene dye.

Through elongating the end or side alkyl chains of dye molecules, we decorate anatase nanocrystals with a thicker organic assembly featuring a smaller tilt angle of the D–π-A backbone with respect to the surface normal, which retards the interfacial charge recombination and confers a higher photovoltage output on mesoscopic cobalt solar cells displaying an over 10% power conversion efficiency at the AM1.5G conditions.

In this work, a metal-mediated assembling strategy has been used to organize a series of new assemblies based on tetrapyridylporphyrin (ZnP) on nanostructured TiO2 electrode surfaces, wherein the metal ions (M, M = Zn2+, Cd2+, Hg2+ and Mn2+) bridge the pyridyl units of ZnP and (E)-4-[(pyridin-4-ylmethylene)-amino]benzoic acid (A), resulting in a ZnP–M–A assembled mode. The assembled structures were characterized by transmission electron microscopy (TEM), computational calculations, energy-dispersive X-ray spectroscopy (EDX), IR, UV-vis absorption and fluorescence spectra. The performances of the assembly-sensitized solar cells were also measured under an irradiance of 100 mW cm−2 AM 1.5G sunlight. Photoelectrochemical results reveal a relatively large photocurrent of the ZnP–Mn–A device. Simultaneously, a large open-circuit photovoltage and a significantly improved conversion efficiency of the ZnP–Zn–A device are also observed. These findings may serve as another good testing ground for the fabrication of supramolecular solar cells in future.

The rigidification of π-conjugated segments represents a feasible tactic towards energy-level engineering of organic D-π-A dyes in mesoscopic titania solar cells. In this work, comparions of four dyes with the di(3-hexylthiophene), dihexyldithienosilole, dihexylcyclopentadithiophene and N-hexyldithienopyrrole linkers have revealed some general influences of π-linker rigidification on the optoelectronic features of titania solar cells employing a cobalt(II/III) redox electrolyte, in terms of energetic and kinetic viewpoints. Compared to a dye with the di(3-hexylthiophene) linker, its three counterparts with rigidified dithiophene blocks present bathochromic and hyperchromic absorptions of solar photons. Transient absorption measurements have shown that the incorporation of Si-, C- and N-bridged dithiophene segments decelerates the dye regeneration kinetics. The rigidification of π-conjugated dithiophene linkers brings forth a general open-circuit photovoltage diminishment, in the range from 60 to 190 mV. Further insightful impedance analyses have disclosed that the open-circuit photovoltage reduction, due to the π-linker alternation from di(3-hexylthiophene) to N-hexyldithienopyrrole, is predominantly caused by an adverse downward displacement of the titania conduction band edge, despite a positive contribution from attenuated charge recombination at the titania/electrolyte interface.