Does the triphenylamine-based D35 dye sensitizer form aggregates on metal-oxide surfaces?

• Absorption and emission properties of D35 dye-sensitized zirconia and titania nanoparticles are examined.
• Small population of J-aggregates identified, with evidence of dye monomer to dye aggregate energy transfer occurring.
• D35 dye monomer's excited state lifetime on zirconia is measured to be 1.42 ns.
• D35 dye monomer's electron injection quantum yield on titania is estimated to be 0.89.

The absorption and emission properties of the D35 organic dye sensitizer attached to zirconia and titania nanoparticles are examined. The dye-sensitized nanoparticles are prepared in the presence and absence of the chenodeoxycholic acid (CDCA) co-adsorbent to control the amount of dye adsorbed to the metal-oxide surface. The broadening of the dye's optical absorption band on the long wavelength side for layers without CDCA co-adsorbent demonstrates that J-aggregates are formed. Fast energy transfer is found to occur from the excited dye monomers to the dye aggregates. From the time-resolved fluorescence decay curves recorded for the dye attached to zirconia, the isolated dye monomer is determined to have an excited state lifetime of 1.42 ns, whereas the largest dye aggregates have shorter lifetimes (≤1.00 ns). From the time-resolved fluorescence decay curves recorded for the dye attached to titania, the isolated dye monomer is estimated to have an electron injection rate of 6 ns−1 and electron injection quantum yield of 0.89. The results provide a clear view of the light-harvesting behaviour for the triphenylamine-based D35 dye, which is commonly employed within dye-sensitized solar cells.

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