3 research outputs found
Multilayer Epitaxial Growth of Lead Phthalocyanine and C<sub>70</sub> Using CuBr as a Templating Layer for Enhancing the Efficiency of Organic Photovoltaic Cells
The
molecular orientation and crystallinity of donor and acceptor
molecules are important for high-efficiency organic photovoltaic cells
(OPVs) because they significantly influence both the absorption of
light and charge-transport characteristics. We report that the templating
effect extends to multilayers to increase the crystallinity and to
modify the orientation of the crystals of lead phthalocyanine (PbPc)
and C<sub>70</sub> layers at the same time by adopting CuBr as a new
templating layer on indium tin oxide (ITO). The formation of a monoclinic
phase with a preferred orientation of (320) for PbPc and a fcc phase
with a preferred orientation of (220) for C<sub>70</sub> on the PbPc
layer is revealed by X-ray diffraction (XRD) patterns. The multilayer
epitaxy results in an increase of the exciton diffusion lengths from
5.6 to 8.8 nm for PbPc and from 6.9 to 13.8 nm for C<sub>70</sub> to
enhance the power conversion efficiency (PCE) of the planar heterojunction
OPVs composed of PbPc and C<sub>70</sub> from 1.4 to 2.3%. The quasi-epitaxy
model is proposed to explain the multilayer epitaxy
Highly Efficient Vacuum-Processed Organic Solar Cells Containing Thieno[3,2‑<i>b</i>]thiophene-thiazole
Two novel electron-donor molecules
based on donor−π-conjugated linker–acceptor structure
with compact packing and intramolecular charge-transfer characteristics
were synthesized for the preparation of efficient organic solar cells.
The donor molecules featuring an electron-rich triphenyl amine as
the electron-donor unit, dicyanovinylene as the acceptor unit, and
Ï€-conjugated linkers of thienothiophene, thiophene, and thiazole
units were synthesized. The π-conjugated linkers were carefully
designed to have a planar structure, an efficient conjugation length,
and appropriate energy levels for a compact packing in the solid state.
The vacuum-processed solar cells fabricated using the donor molecules
of DTTh and DTTz exhibited average power-conversion efficiencies (PCEs)
of 5.4 and 6.2% (the highest PCE obtained was 6.37%) under AM 1.5G
illumination with an intensity of 100 mW cm<sup>–2</sup>
Enhancement of the Fill Factor through an Increase of the Crystallinity in Fullerene-Based Small-Molecule Organic Photovoltaic Cells
We report that the crystallinity
of C<sub>70</sub> is improved significantly if CuI is used as a templating
layer, leading to remarkable enhancement of hole mobilities from 8.32
× 10<sup>–6</sup> to 3.26 × 10<sup>–5</sup> cm<sup>2</sup>/(V s). As a result, the use of the templating layer
in C<sub>70</sub>-based solar cells with low donor concentration resulted
in significant improvement of the fill factor from 0.51 to 0.57 and
the power conversion efficiency from 5.56% to 6.23% under simulated
AM 1.5G, 1 sun irradiation. This result demonstrates that the CuI
templating layer is effective at improving the crystallinity of the
fullerene derivatives as well as the donor materials