4 research outputs found
Discrepancy of Optimum Ratio in Bulk Heterojunction Photovoltaic Devices: Initial Cell Efficiency vs Long-Term Stability
Organic
photovoltaic devices are difficult to commercialize because
of their vulnerability to chemical degradation related with oxygen
and water and to physical degradation with aging at high temperatures.
We investigated the photophysical degradation behaviors of a series
of poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl C61-butyric acid methyl
ester (PC<sub>60</sub>BM) bulk heterojunctions (BHJs) as a model system
according to the donor–acceptor ratio. We found that the optimum
P3HT:PC<sub>60</sub>BM ratio in terms of long-term stability differs
from that in terms of initial cell efficiency. On the basis of cell
performance decays and time-resolved photoluminescence measurements,
we investigated the effects of oxygen and material self-aggregation
on the stability of an organic photovoltaic device. We also observed
the changes in morphological geometry and analyzed the surface elements
to verify the mechanisms of degradation
Direct Low-Temperature Growth of Single-Crystalline Anatase TiO<sub>2</sub> Nanorod Arrays on Transparent Conducting Oxide Substrates for Use in PbS Quantum-Dot Solar Cells
We report on the direct growth of
anatase TiO<sub>2</sub> nanorod
arrays (A-NRs) on transparent conducting oxide (TCO) substrates that
can be directly applied to various photovoltaic devices via a seed
layer mediated epitaxial growth using a facile low-temperature hydrothermal
method. We found that the crystallinity of the seed layer and the
addition of an amine functional group play crucial roles in the A-NR
growth process. The A-NRs exhibit a pure anatase phase with a high
crystallinity and preferred growth orientation in the [001] direction.
Importantly, for depleted heterojunction solar cells (TiO<sub>2</sub>/PbS), the A-NRs improve both electron transport and injection properties,
thereby largely increasing the short-circuit current density and doubling
their efficiency compared to TiO<sub>2</sub> nanoparticle-based solar
cells
Iridium Complexes Containing Bis(imidazoline thione) and Bis(imidazoline selone) Ligands for Visible-Light-Induced Oxidative Coupling of Benzylamines to Imines
Novel
iridium(III) complexes containing bis(N-heterocyclic carbene),
bis(imidazoline thione) <b>L2</b>, and bis(imidazoline selone) <b>L3</b> were prepared. The iridium complexes bearing <b>L2</b> and <b>L3</b> showed the significant absorption of visible
light with maximum intensity at ∼460 nm. Bis(2-(2′-benzothienyl)pyridinato)iridium(III)
complexes (<b>Ir-6</b>) with <b>L3</b> showed excellent
ability as a photosensitizer of visible light. Under blue LED irradiation
with maximum emission at 460 nm, 0.25 mol % <b>Ir-6</b> showed
94% conversion of benzylamine for 5 h at room temperature. Through
mechanistic studies, it was suggested that the photoinduced oxidative
coupling of benzylamine by <b>Ir-6</b> follows a singlet oxygen
pathway. The excellent performance of <b>Ir-6</b> originated
from the efficient visible light absorption at 460 nm and the enhanced
triplet state due to the heavy-atom effect of <b>L3</b>. This
work shows that bis(imidazoline thione) and bis(imidazoline selone)
can be efficient ligands for tuning the optical properties of iridium(III)
complexes
Hollow Microporous Organic Networks Bearing Triphenylamines and Anthraquinones: Diffusion Pathway Effect in Visible Light-Driven Oxidative Coupling of Benzylamines
Hollow microporous organic networks
were prepared by using silica
spheres as the template and tris(4-ethynylphenyl)amine and 2,6-diiodo-9,10-anthraquinone
as the building blocks for the Sonogashira coupling. The resultant
materials bearing triphenylamine and anthraquinone moieties showed
efficient visible light absorption and catalytic activities in the
photochemical oxidative coupling of benzylamines. Through the comparison
studies of hollow and nonhollow catalytic materials, the diffusion
pathway effect of the substrates was clearly observed in the photochemical
conversion of benzylamines