Spectroscopy and Dynamics of YD2-o-C8 in Solution and Interacting with Alumina Nanoparticles Electrode

Abstract

In this paper, we report on the absorption, emission, and photodynamics of a push−pull zinc porphyrin (YD2-o-C8) in solution and adsorbed on Al 2 O 3 (alumina) nanoparticles (NPs). The shift in the absorption and emission spectra for the dye adsorbed on alumina NPs with respect to the solution suggests the presence of an anchoring effect of the dye to the NPs' surface. Indeed, different molecular populations (monomers and aggregates) coexist for the solid film, as it is confirmed by both steady-state and timeresolved measurements. The emission decays, while monoexponential in acetonitrile (ACN) solution (τ = 1.5 ns) become multiexponential (140 and 550 ps) for the dye interacting with the alumina NPs. These lifetime values increase (210 and 930 ps) upon addition of CDCA (a disaggregating agent). The deactivation (vibrational cooling) of the hot S 1 to cold S 1 state, which occurs in 4−6 ps in ACN, shows a biexponential behavior in the solid state (2 ps, 20 ps). These two ps components, whose values upon excitation at 460 nm do not change with respect to those observed without CDCA, become longer in the presence of the coadsorbent and exciting at 640 nm (4 ps, 50−60 ps), where the aggregates mostly absorb. The charge separation (2 ps in ACN, 15 ps in toluene) becomes faster in the solid state in absence of CDCA (∼500 and 110 fs exciting at 460 and 640 nm, respectively), while, by adding the coadsorbent, the process occurs on a time scale that is below our time-resolution (<50 fs). The obtained results are of potential interest to understand the dynamics of the porphyrin used in the up-to-now world-record-efficient dye-sensitized solar cell (DSSC).

Panchromatic Sensitization with ZnII Porphyrin‐Based Photosensitizers for Light‐Driven Hydrogen Production

“…A similar value of 2–6 ps has been reported by di Nunzio et al. for the similar YD2‐ o ‐C8 PS . Lastly, we observed a loss of amplitude in the 478 nm shoulder of the ESA with a 1300 ps time constant, indicating that the molecule underwent ISC to the triplet manifold, which then persisted past the duration of the experiment.…”

“…Femtosecond transient absorption (TA) control experiments of Bodipy‐dye (Figure S17) and YD2‐ o ‐C8 confirmed prior observations of their excited state spectra and dynamics. The Bodipy‐dye exhibited transient signals that decayed slowly with the 1 ππ*’s 5–7 ns excited state lifetime, controlled by radiative and nonradiative internal conversion to the ground state.…”

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

“…Because the experimental results point to a low population of J-aggregates, it seems that the attractive intermolecular interactions between the tilted dye molecules are generally not sufficient to overcome the cyanoacrylic acid-surface interaction that favours a perpendicular dye orientation. Furthermore, our results show that the butoxyl chains of D35 do not completely prevent aggregate formation, with a similar conclusion arrived at by di Nunzio et al for a porphyrin dye containing octoxyl chains [44]. Therefore, further research into more effective anti-aggregation chemical groups is desirable.…”

Ultrafast and slow charge recombination dynamics of diketopyrrolopyrrole–NiO dye sensitized solar cells

“…30 Time-resolved emission (TCSPC) decays for all three dyes were fitted with double exponential function ( Figure S3), which show that the fluorescence lifetimes decreased with increasing electron withdrawing ability of the DPP substituent: from DPPBr (τ = 9.65 ns, 89%) to DPPCN2 with a conjugated acceptor group (τ = 0.78 ns, 88%) and DPP-NDI with a non-conjugated, separate secondary electron acceptor (NDI) (τ = 260 ps, 96%). 37 Binding on NiO induces a 50 nm red-shift of the emission maximum (peak from 580 nm DCM to 630 nm on NiO). 1,34-36 All three photocathodes were found to be photoluminescent.…”