Non‐Covalent Postfunctionalization of Dye Layers on TiO₂ — A Tool for Enhancing Injection in Dye‐Sensitized Solar Cells

Abstract

We report on newly tailored dye layers, which were employed, on one hand, for covalent deposition and, on the other hand, for non‐covalently post‐functionalizing TiO2 nanoparticle films. Our functionalization concept enabled intermixing a stable covalent attachment of a first layer with a highly versatile and reversible hydrogen bonding through the Hamilton receptor–cyanuric acid binding motif as a second layer. Following this concept, we integrated step‐by‐step a first porphyrin layer and a second porphyrin/BODIPY layer. The individual building blocks and their corresponding combinations were probed with regard to their photophysical properties, and the most promising combinations were implemented in dye‐sensitized solar cells (DSSCs). Relative to the first porphyrin layer adding the second porphyrin/BODIPY layers increased the overall DSSC efficiency by up to 43 %.

Synthesis and Characterization of Bola‐Amphiphilic Porphyrin‐Perylenebisimide Architectures

“…The synthesis of the required porphyrin 4 was previously reported by our group [40] . 5 and 6 were obtained by imidization under Langhals conditions with 4‐iodoaniline, starting from the respective anhydrides according to literature known procedures [41,42] .…”

“…[35,38,39] The synthesis of the required porphyrin 4 was previously reported by our group. [40] 5 and 6 were obtained by imidization under Langhals conditions with 4-iodoaniline, starting from the respective anhydrides according to literature known procedures. [41,42] Saponification of 4 was performed with LiOH in a THF/H 2 O mixture, yielding 7 in nearly quantitative yields.…”

Hierarchical Assembly and Sensing Activity of Patterned Graphene‐Hamilton Receptor Nanostructures

“…With remarkable hydrogen bonding interactions (binding constant of up to 10 6 m –1 ) [ 19–21 ] in between, the well‐established Hamilton receptor/cyanurate recognition pair stands out as a highly attractive anchoring couple ( Figure b). The very strong interaction, provided by six complementary H‐bonding sites, [ 19 ] renders numerous possibilities for the construction of novel hierarchical architectures or hybrid materials such as supramolecular wires, [ 22,23 ] self‐assembled nanoparticles (NP), [ 24,25 ] donor–acceptor pairs consisting of fullerenes and porphyrins, [ 21,22,26 ] and the solubilization/separation of carbon nanotubes. [ 27 ] Moreover, in view of the supramolecular recognition between the Hamilton‐receptor and cyanurate/barbiturate unit, great potential for sensing could be straightforwardly envisaged.…”