1 research outputs found
Dual Functionality of BODIPY Chromophore in Porphyrin-Sensitized Nanocrystalline Solar Cells
A new organic dye (BET) was synthesized and coadsorbed
on TiO<sub>2</sub> nanoparticles to make mixed BET/porphyrin-sensitized
solar
cells (DSCs). The BET is a boron dipyrromethene compound with one
benzoic acid group attached to the meso position for its binding to
the TiO<sub>2</sub> nanoparticles and two ethyl groups in the 3 and
3′ positions of pyrrolic units to broaden its absorption. Two
ethyl groups are in the cis position, as revealed by its single-crystal
X-ray diffraction analysis. The BET exhibits strong absorption in
the green light region with an absorption maximum at 528 nm in CH<sub>2</sub>Cl<sub>2</sub>, which is complementary to the absorption spectrum
of porphyrin dyes. When the BET coadsorbs on the TiO<sub>2</sub> nanoparticles
with porphyrin dyes (TMPZn and LD12), the power conversion efficiencies
increase from 1.09% to 2.90% for TMPZn-sensitized solar cells and
from 6.65% to 7.60% for LD12-sensitized solar cells, respectively.
The IPCE of the devices in the green light region increases dramatically
due to the cosensitizing effect of BET. The fluorescence of BET in
solution is partially quenched and that of porphyrin is enhanced in
the presence of BET dye, indicating an intermolecular energy transfer
from BET to the porphyrin dyes. The direct electron injection from
BET to the TiO<sub>2</sub> conduction band was rather poor; only negligible
photocurrent was observed. Comparative studies of absorption spectra
on the TiO<sub>2</sub> nanoparticle films and electrochemical impedance
at the dye/TiO<sub>2</sub> interface also indicate that the BET is
an excellent coadsorber to prevent the aggregation of porphyrin dyes.
An intermolecular energy transfer model is proposed to account for
the observed photovoltaic enhancement of the cosensitization system