Ultrafast heterogeneous electron transfer reactions: Comparative theoretical studies on time- and frequency-domain data

Abstract

Recent theoretical studies on linear absorption spectra of dye-semiconductor systems ͓perylene attached to nanostructured TiO 2 , L. Wang et al., J. Phys. Chem. B 109, 9589 ͑2005͔͒ are extended here in different respects. Since the systems show ultrafast photoinduced heterogeneous electron transfer the time-dependent formulation used to compute the absorbance is also applied to calculate the temporal evolution of the sub-100 fs charge injection dynamics after a 10 fs laser-pulse excitation. These studies complement our recent absorption spectra fit for two perylene bridge-anchor group TiO 2 systems. Moreover, the time-dependent formulation of the absorbance is confronted with a frequency-domain description. The latter underlines the central importance of the self-energy caused by the coupling of the dye levels to the semiconductor band continuum. The used model is further applied to study the effect of different parameters such as ͑1͒ the dependence on the reorganization energies of the involved intramolecular transitions, ͑2͒ the effect of changing the transfer integral which couples the excited dye state with the band continuum, and ͑3͒ the effect of the concrete form of the semiconductor band density of states. Emphasis is also put on the case where the charge injection level of the dye is near or somewhat below the band edge. This nicely demonstrates the change from a structureless absorption to a well-resolved vibrational progression including characteristic shifts of the absorption lines which are a direct measure for the dye-semiconductor coupling.

Theory of ultrafast photoinduced heterogeneous electron transfer

“…Ref. [29]), indicating the validity of the wide-band approximation at the present mid-band position of the injection level.…”

“…The present paper continues our theoretical studies on HET with particular emphasis on the perylene-TiO 2 system [24][25][26][27][28][29]. To account for the optical excitation, for subsequent electron-vibrational quantum dynamics, the formation of an electron distribution in the semiconductor band continuum, its detection by two-photon photon emission spec-F o r P e e r R e v i e w O n l y troscopy, and for femtosecond laser pulse control a model of reduced dimensionality has to be applied.…”

“…we have already applied in our former studies [24][25][26][27][28][29]. Therefore, we introduce a notation by concentrating on the state of the single electron to be transferred.…”

“…We will tackle this problem as described in [24][25][26][27][28][29]. Therefore, the k-dependence of the C kM (t) is replaced by a frequency dependence leading to the quantities C M (Ω; t).…”

Ab initio study of exciton transfer dynamics from a core–shell semiconductor quantum dot to a porphyrin-sensitizer

“…An intermediate description between the rate theories and molecular dynamics is provided by the reduced density matrix methods [38,[41][42][43][62][63][64], which couple several explicit electronic or vibrational modes to a thermal bath of many modes.…”