11 research outputs found
Fluorescent Organic Nanoparticles Based on Branched Small Molecule: Preparation and Ion Detection in Lithium-Ion Battery
Fluorescent organic nanoparticles
(FONs) as a new class of nanomaterials
can provide more advantages than molecule based probes. However, their
applications in specific metal ion detection have rarely been exploited.
We design and synthesize a branched small-molecule compound with triazole
as a core and benzothiadiazole derivative as branches. By a facile
reprecipitation method, nanoparticles (NPs) of this compound can be
prepared in aqueous solutions, which can show high selectivity and
sensitivity to FeÂ(III) ions based on fluorescence quenching. In addition,
the fluorescence intensity of these NPs is resistant to pH changes
in solutions. Such characters of this kind of NPs can be utilized
in Fe<sup>3+</sup> impurity detection in a promising cathode material
(LiFePO<sub>4</sub>) for lithium ion batteries. When exposed to Fe<sup>3+</sup>, both the triazole and benzothiadiazole groups contribute
to the fluorescence quenching of NPs, but the former one plays a more
important role in Fe<sup>3+</sup> impurity detection. The sensing
mechanism has also been investigated which indicates that a Fe-organic
complex formation may be responsible for such sensing behavior. Our
findings demonstrate that specific metal ion detection can be realized
by FONs and have extended the application field of FONs for chemical
sensing in aqueous solutions
Fluorescence Resonance Energy Transfer in a Binary Organic Nanoparticle System and Its Application
Fluorescent organic nanoparticles
have a much better photostability
than molecule-based probes. Here, we report a simple strategy to detect
chemicals and biomolecules by a binary nanoparticle system based on
fluorescence resonance energy transfer (FRET). PolyÂ(9,9-di-<i>n</i>-octylfluorenyl-2,7-diyl) (PFO, energy donor) and poly
[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV, energy
acceptor) are utilized to prepare the binary nanoparticle system through
a reprecipitation method. Since the FRET process is strongly distance-dependent,
a change in the interparticle distance between the two kinds of nanoparticles
after introduction of analytes will alter the FRET efficiency. The
response of the binary nanoparticle system to cationic polyelectrolytes
was investigated by monitoring the FRET efficiency from PFO to MEH-PPV
nanoparticles and the fluorescence color of the nanoparticle solutions.
Furthermore, the cationic polyelectrolyte pretreated binary nanoparticle
system can be used to detect DNA by desorption of nanoparticles from
the polyelectrolyte’s chains and the detection concentration
can go down to 10<sup>–14</sup> M. Thus, the binary nanoparticle
system shows great promise for applications in chemical sensing or
biosensing
Solution-Processed White Organic Light-Emitting Diodes with Enhanced Efficiency by Using Quaternary Ammonium Salt Doped Conjugated Polyelectrolyte
Solution-processed white organic
light emitting diodes (WOLEDs) with quaternary ammonium salt doped
water/alcohol soluble conjugated polyelectrolyte, polyÂ[(9,9-bisÂ(3′-((<i>N,N</i>-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-<i>alt</i>-2,7-(9,9-dioctylfluoren)] dibromide (PFNBr), as electron
transport material has been fabricated. Compared with the undoped
devices, the performances of such devices with a doped electron transport
layer have been dramatically improved to be nearly twice high in luminous
efficiency and nearly one-third in response time when the weight ratio
of PFNBr to tetraethylammonium bromide (TEAB) was 10:3. Four kinds
of quaternary ammonium salts have been investigated to be dopants
in the conjugated polyelectrolyte electron transport layer. It has
been shown that both the anions and the cations of quaternary ammonium
salts can influence the device performance. The dopant who has both
a smaller anion and a smaller cation size can exhibit a better device
performance. In addition, ultraviolet photoelectron spectroscopy measurement
and single-carrier device testing have been employed to investigate
the reason why such quaternary ammonium salt dopants can make an obvious
improvement in the device performance of WOLEDs. These findings will
be beneficial to the progress in design and fabrication of solution-processed
WOLEDs suitable for lighting
Low-Temperature, Solution-Processed Hole Selective Layers for Polymer Solar Cells
A new method is reported for preparing solution-processed
molybdenum oxide (MoO<sub>3</sub>) hole selective layer (HSL). Via
combustion processing at low annealing temperatures, the obtained
MoO<sub>3</sub> HSL exhibits a high charge-transporting performance
similar to polyÂ(ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)
but overcoming its defect to device stability. The combustion precursor
solution using ammonium heptamolybdate as the metal source, acetylacetone
as a ‘fuel’, and nitric acid as an oxidizer can largely
reduce the temperature for transformation of the polyoxomolybdate
to α-phase MoO<sub>3</sub>. Furthermore, when a small amount
of PEDOT:PSS has been introduced into the combustion precursor solution
to improve the film morphology, the derived film can exhibit a flat
and continuous surface morphology with coexistence of α- and
β-MoO<sub>3</sub> after being annealed at a low temperature
(150 °C). The simplicity, rapidness, and effectiveness of our
method together with the low annealing temperature needed make it
promising for the roll-to-roll manufacture of polymer solar cells
Effect of Non-fullerene Acceptors’ Side Chains on the Morphology and Photovoltaic Performance of Organic Solar Cells
Three indacenodithienoÂ[3,2-<i>b</i>]Âthiophene (IT) cored small molecular acceptors (ITIC-SC6,
ITIC-SC8, and ITIC-SC2C6) were synthesized, and the influence of side
chains on their performances in solar cells was systematically probed.
Our investigations have demonstrated the variation of side chains
greatly affects the charge dissociation, charge mobility, and morphology
of the donor:acceptor blend films. ITIC-SC2C6 with four branched side
chains showed improved solubility, which can ensure the polymer donor
to form favorable fibrous nanostructure during the drying of the blend
film. Consequently, devices based on PBDB-ST:ITIC-SC2C6 demonstrated
higher charge mobility, more effective exciton dissociation, and the
optimal power conversion efficiency up to 9.16% with an FF of 0.63,
a <i>J</i><sub>sc</sub> of 15.81 mA cm<sup>–2</sup>, and a <i>V</i><sub>oc</sub> of 0.92 V. These results
reveal that the side chain engineering is a valid way of tuning the
morphology of blend films and further improving PCE in polymer solar
cells
AIE-Active Fluorene Derivatives for Solution-Processable Nondoped Blue Organic Light-Emitting Devices (OLEDs)
A series
of fluorene derivatives end-capped with diphenylamino
and oxadiazolyl were synthesized, and their photophysical and electrochemical
properties are reported. Aggregation-induced emission (AIE) effects
were observed for the materials, and bipolar characteristics of the
molecules are favored with measurement of carrier mobility and calculation
of molecular orbitals using density functional theory (DFT). Using
the fluorene derivatives as emitting-layer, nondoped organic light-emitting
devices (OLEDs) have been fabricated by spin-coating in the configuration
ITO/PEDOT:PSSÂ(35 nm)/PVKÂ(15 nm)/<b>PhN-OFÂ(</b><i><b>n</b></i><b>)-Oxa</b>(80 nm)/SPPO13Â(30 nm)/CaÂ(8 nm)/AlÂ(100
nm) (<i>n</i> = 2–4). The best device with <b>PhN-OFÂ(</b><b>2</b><b>)-Oxa</b> exhibits a maximum
luminance of 14 747 cd/m<sup>2</sup>, a maximum current efficiency
of 4.61 cd/A, and an external quantum efficiency (EQE) of 3.09% in
the blue region. Investigation of the correlation between structures
and properties indicates that there is no intramolecular charge transfer
(ICT) increase in these molecules with the increase of conjugation
length. The device using material of the shortest conjugation length
as emitting-layer gives the best electroluminescent (EL) performances
in this series of oligofluorenes
Improving the Performance of Layer-by-Layer Organic Solar Cells by n‑Doping of the Acceptor Layer
Molecular
dopants can effectively improve the performance
of organic
solar cells (OSCs). Here, PM6/BTP-eC9-4Cl-based OSCs are fabricated
by a layer-by-layer (LbL) deposition method, and the electron acceptor
BTP-eC9-4Cl layer is properly doped by n-type dopant benzyl viologen
(BV) or [4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl]dimethyl-amine
(N-DMBI-H). The power conversion efficiency (PCE) of OSCs increases
from 16.80 to 17.61 or 17.84% when the acceptor layer is doped by
BV (0.01 wt %) or N-DMBI-H (0.01 wt %), respectively. At the optimal
doping concentration, the device exhibits more balanced charge transport,
fewer bimolecular recombinations, faster charge separation and transfer,
and better stability. This doping strategy has good universality;
when the acceptor layer L8-BO of LbL OSCs is doped by 0.01 wt % BV
or 0.01 wt % N-DMBI-H, the PCE increases from 17.49 to 18.35 or 18.25%,
respectively. All in all, our studies have demonstrated that the doping
strategy is effective in enhancing the performance of OSCs
Enhancing the Efficiency of Polymer Solar Cells by Incorporation of 2,5-Difluorobenzene Units into the Polymer Backbone via Random Copolymerization
A series
of conjugated polymers <b>P0</b>, <b>P5</b>, and <b>P7</b> containing 0, 5, and 7 mol % 2,5-difluorobenzene units,
respectively, were prepared and utilized as electron donors in polymer
solar cells. Incorporation of a small amount of 2,5-difluorobenzene
unit into the backbone of donor polymers can significantly increase
their planarity and crystallinity as well as decrease their solubility.
The improved molecular conformation can markedly affect the morphology
of polymer:PC<sub>71</sub>BM blend films. After incorporation of 5
mol % 2,5-difluorobenzene unit into the backbone of donor polymers,
the domain size of blend films became smaller and the hole mobility
increased. Increasing the content of 2,5-difluorobenzene to 7 mol
% can further decrease the solubility of resulting polymers and resulted
in poor solution processability. As a result, <b>P5</b>-based
devices achieved a power conversion efficiency (PCE) of 8.5%, whereas <b>P0</b> based devices gave a PCE of 7.8%
Exploiting Noncovalently Conformational Locking as a Design Strategy for High Performance Fused-Ring Electron Acceptor Used in Polymer Solar Cells
We have developed
a kind of novel fused-ring small molecular acceptor,
whose planar conformation can be locked by intramolecular noncovalent
interaction. The formation of planar supramolecular fused-ring structure
by conformation locking can effectively broaden its absorption spectrum,
enhance the electron mobility, and reduce the nonradiative energy
loss. Polymer solar cells (PSCs) based on this acceptor afforded a
power conversion efficiency (PCE) of 9.6%. In contrast, PSCs based
on similar acceptor, which cannot form a flat conformation, only gave
a PCE of 2.3%. Such design strategy, which can make the synthesis
of small molecular acceptor much easier, will be promising in developing
a new acceptor for high efficiency polymer solar cells
Nonfullerene Acceptors with Enhanced Solubility and Ordered Packing for High-Efficiency Polymer Solar Cells
The performance of
polymer solar cells (PSCs) is commonly improved
using additives or annealing treatment. However, these processes are
accompanied by disadvantages, including poor reproducibility and stability.
Herein, a molecular design strategy is proposed to obtain additive-
and annealing-free PSCs. <b>IDTOT2F</b> containing two alkoxyl
side chains at the central unit of the nonfullerene acceptor <b>IDTT2F</b> was developed. This molecular design results in excellent
solubility in solutions, ordered molecular packing in films, slightly
elevated energy levels, and a higher film absorption coefficient.
Compared with its counterpart <b>IDTT2F</b>, its improved solubility
provides an active layer with better morphology, its ordered molecular
packing enhances the charge mobility in blend films, and its slightly
elevated energy level furnishes a higher open-circuit voltage of devices.
As a result, <b>IDTOT2F</b>-based devices display a maximum
power conversion efficiency of 12.79%, which is one of the highest
values reported for a PSC fabricated without any extra treatment