2 research outputs found
Exciton Generation/Dissociation/Charge-Transfer Enhancement in Inorganic/Organic Hybrid Solar Cells by Robust Single Nanocrystalline LnP<sub><i>x</i></sub>O<sub><i>y</i></sub> (Ln = Eu, Y) Doping
Low-temperature
solution-processed photovoltaics suffer from low efficiencies because
of poor exciton or electron–hole transfer. Inorganic/organic
hybrid solar cell, although still in its infancy, has attracted great
interest thus far. One of the promising ways to enhance exciton dissociation
or electron–hole transport is the doping of lanthanide phosphate
ions. However, the underlying photophysical mechanism remains poorly
understood. Herein, by applying femtosecond transient absorption spectroscopy,
we successfully distinguished hot electron, less energetic electron,
hole transport from electron–hole recombination. Concrete evidence
has been provided that lanthanide phosphate doping improves the efficiency
of both hot electron and “less energetic” electron transfers
from donor to acceptor, but the hole transport almost remains unchanged.
In particular, the hot electron transfer lifetime was shortened from
30.2 to 12.7 ps, that is, more than 60% faster than pure TiO<sub>2</sub> acceptor. Such improvement was ascribed to the facts that the conduction
band (CB) edge energy level of TiO<sub>2</sub> has been elevated by
0.2 eV, while the valence band level almost remains unchanged, thus
not only narrowing the energy offset between CB levels of TiO<sub>2</sub> and P3HT, but also meanwhile enlarging the band gap of TiO<sub>2</sub> itself that permits one to inhibit electron–hole recombination
within TiO<sub>2</sub>. Consequently, lanthanide phosphate doped TiO<sub>2</sub>/P3HT bulk-heterojunction solar cell has been demonstrated
to be a promising hybrid solar cell, and a notable power conversion
efficiency of 2.91% is therefore attained. This work indicates that
lanthanide compound ions can efficiently facilitate exciton generation,
dissociation, and charge transport, thus enhancing photovoltaic performance
Top-down Strategy toward Versatile Graphene Quantum Dots for Organic/Inorganic Hybrid Solar Cells
Metal oxide nanocrystals have been
pursued for various applications
in photovoltaics as a buffer layer. However, it remains a challenging
task to adjust their energy levels to achieve a better match of the
donor–acceptor system. Herein, we report the fabrication of
graphene quantum dots (GQDs) with bright blue photoluminescence by
a top-down strategy based on laser fragmentation with posthydrothermal
treatment. The GQDs demonstrate appropriate energy level positions
and are used as an intermediate buffer layer between TiO<sub>2</sub> and P3HT to form a cascade energy level architecture. The introduction
of the GQDs into a bulk heterojunction hybrid solar cell has led to
an enhancement of the power conversion efficiency