1 research outputs found
Field-Induced Fluorescence Quenching and Enhancement of Porphyrin Sensitizers on TiO<sub>2</sub> Films and in PMMA Films
Three
highly efficient porphyrin sensitizersî—¸YD2, YD2-oC8,
and YD30, either sensitized on TiO<sub>2</sub> films or embedded in
PMMA filmsî—¸were investigated using electrophotoluminescence
(E-PL) spectra. Under both thin-film conditions, on application of
an external electric field we observed the quenching of fluorescence
of push–pull porphyrins (YD2 and YD2-oC8) and a slightly enhanced
fluorescence of the reference porphyrin without an electron donor
group (YD30). A nonfluorescent state with charge separation (CS) is
proposed to be involved in both YD2 and YD2-oC8 systems so that the
electron injection becomes accelerated in the presence of a strong
electric field. In contrast, the retardation of the nonradiative process
not involving a CS state was the reason for the field-induced enhancement
of fluorescence of YD30. The extent of fluorescence quenching of YD2-oC8
was greater than that of YD2 on TiO<sub>2</sub> films, indicating
that the <i>ortho</i>-substituted long alkoxyl chains play
a key role to accelerate the consecutive electron injection involving
the CS state. Our E-PL results indicate that a field-induced variation
of fluorescent intensity is related to the efficiency of conversion
of solar energy and that further improvement of the performance of
devices containing push–pull porphyrin dyes is achievable under
an applied electric field