14 research outputs found
Covalently Bound Clusters of Alpha-Substituted PDIî—¸Rival Electron Acceptors to Fullerene for Organic Solar Cells
A cluster
type of electron acceptor, TPB, bearing four α-perylenediimides
(PDIs), was developed, in which the four PDIs form a cross-like molecular
conformation while still partially conjugated with the BDT-Th core.
The blend TPB:PTB7-Th films show favorable morphology and efficient
charge dissociation. The inverted solar cells exhibited the highest
PCE of 8.47% with the extraordinarily high <i>J</i><sub>sc</sub> values (>18 mA/cm<sup>2</sup>), comparable with those
of
the corresponding PC<sub>71</sub>BM/PTB7-Th-based solar cells
Electron Acceptors Based on α‑Substituted Perylene Diimide (PDI) for Organic Solar Cells
Perylene
diimide (PDI) derivatives functionalized at the ortho-position
(αPPID, αPBDT) were synthesized and used as electron acceptors
in non-fullerene organic photovoltaic cells. Because of the good planarity
and strong π-stacking of ortho-functionalized PDI, the αPPID
and αPBDT exhibit a strong tendency to form aggregates, which
endow the materials with high electron mobility. The inverted OPVs employing αPDI-based compounds as the acceptors
and PBT7-Th as the donor give the highest power conversion efficiency
(PCE) values: 4.92% for αPBDT-based devices and 3.61% for αPPID-based
devices, which are, respectively, 39% and 4% higher than that of their
β-substituted counterparts βPBDT and βPPID. Charge
separation studies show more efficient exciton dissociation at interfaces
between αPDI-based compounds and PTB7-Th. The results suggest
that α-substituted PDI derivatives are more promising electron
acceptors for organic photovoltaic (OPV) components than β-isomers
High Performance Ternary Organic Solar Cells due to Favored Interfacial Connection by a Non-Fullerene Electron Acceptor with Cross-Like Molecular Geometry
The non-fullerene
electron acceptor, TPB, exhibits a unique cross-like
molecular geometry which helps it to stay preferentially at the interfaces
between PTB7-Th and PC<sub>71</sub>BM, when it is used as the third
component in ternary OPV cells. The four PDI units connected to TPB’s
core provide multiple contact points between PTB7-Th and PC<sub>71</sub>BM phases, thus facilitating interfacial charge extraction and improving
the overall PCE to 10.6% from 9.8% after 10% TPB was added as the
third component. This paper describes detailed experimental results
and a model to explain these observations
Enhancement in Open-Circuit Voltage in Organic Solar Cells by Using Ladder-Type Nonfullerene Acceptors
The open-circuit
voltage (<i>V</i><sub>oc</sub>) loss
has always been a major factor in lowering power conversion efficiencies
(PCEs) in bulk heterojunction organic photovoltaic cells (OPVs). A
method to improve the <i>V</i><sub>oc</sub> is indispensable
to achieve high PCEs. In this paper, we investigated a series of perylene
diimide-based ladder-type molecules as electron acceptors in nonfullerene
OPVs. The D–A ladder-type structures described here lock our
Ï€-systems into a planar structure and eliminate bond twisting
associated with linear conjugated systems. This enlarges the interface
energy gap (Δ<i>E</i><sub>DA</sub>), extends electronic
delocalization, and hence improves the <i>V</i><sub>oc</sub>. More importantly, these devices showed an increase in <i>V</i><sub>oc</sub> without compromising either the <i>J</i><sub>sc</sub> or the FF. <b>C5r</b> exhibited a strong intermolecular
interaction and a PCE value of 6.1%. Moreover, grazing-incident wide-angle
X-ray scattering analysis and atomic force microscopy images suggested
that our fused-ring acceptors showed a suitable domain size and uniform
blend films, which were not affected by their rigid molecular structures
Amino Siloxane Oligomer Modified Graphene Oxide Composite for the Efficient Capture of U(VI) and Eu(III) from Aqueous Solution
Poly 3-aminopropyltriethoxysilane
is a highly reactive high-molecular polymer because of the existence
of abundant amino groups, which presents a strong affinity toward
different metal cations. In view of this, the novel poly amino siloxane
oligomer modified graphene oxide composite (PAS–GO) was fabricated
by a facile cross-linking reaction and applied to capture UÂ(VI)/EuÂ(III)
ions from aqueous solution. The interaction mechanisms between the
PAS–GO and UÂ(VI)/EuÂ(III) were elaborated. The modification
by NH<sub>2</sub> increased the sorption sites and improved the sorption
capacities because of the synergistic effect of chelation with UÂ(VI)/EuÂ(III).
X-ray photoelectron spectroscopy revealed that nitrogen groups are
involved in the removal of UÂ(VI)/EuÂ(III) since nitrogen atoms of amine
groups provided the lone pair of electrons with UÂ(VI)/EuÂ(III) species.
The maximum sorption capacity of UÂ(VI) and EuÂ(III) on the PAS–GO
at 298 K calculated by the Langmuir isotherm model was 310.63 and
243.90 mg/g, respectively. The PAS–GO could be repeatedly used
for more than five cycles with slight degradation of sorption. High
sorption efficiency and excellent reusability make the PAS–GO
composite an ideal candidate for the capture of UÂ(VI)/EuÂ(III) from
aqueous solution
Controlled Self-Assembly of Cyclophane Amphiphiles: From 1D Nanofibers to Ultrathin 2D Topological Structures
A novel series of
amphiphilic <b>TC-PEG</b> molecules were
designed and synthesized based on the orthogonal cyclophane unit.
These molecules were able to self-assemble from 1D nanofibers and
nanobelts to 2D ultrathin nanosheets (3 nm thick) in a controlled
way by tuning the length of PEG side-chains. The special structure
of the cyclophane moiety allowed control in construction of nanostructures
through programmed noncovalent interactions (hydrophobic–hydrophilic
interaction and π–π interaction). The self-assembled
nanostructures were characterized by combining real space imaging
(TEM, SEM, and AFM) and reciprocal space scattering (GIWAXS) techniques.
This unique supramolecular system may provide a new strategy for the
design of materials with tunable nanomorphology and functionality
Development and Structure/Property Relationship of New Electron Accepting Polymers Based on Thieno[2′,3′:4,5]pyrido[2,3‑<i>g</i>]thieno[3,2‑<i>c</i>]quinoline-4,10-dione for All-Polymer Solar Cells
Several electron accepting polymers
having weak accepting–strong
accepting (WA-SA) and strong accepting–strong accepting (SA-SA)
monomer alternation were synthesized for studies of structure/property
relationship in all-polymer solar cells. Two kinds of cyclic amide
monomers, 4,10-bisÂ(2-butyloctyl)-thienoÂ[2′,3′:5,6]ÂpyridoÂ[3,4-g]Âthieno-[3,2-<i>c</i>]Âisoquinoline-5,11-dione (TPTI) and 5,11-bisÂ(2-butyloctyl)-thienoÂ[2′,3′:4,5]ÂpyridoÂ[2,3-g]ÂthienoÂ[3,2-<i>c</i>]Âquinoline-4,10-dione (TPTQ), were synthesized as weak
accepting monomers (WA). Difluorinated TPTQ (FTPTQ) and well-known
perylene diimide (PDI) monomers were synthesized as strong electron
accepting monomers (SA). By using 1-chloronaphthalene (CN) as a cosolvent,
the morphology of the polymer blended films can be finely tuned to
achieve better ordering toward face-on mode and favorable phase separation
between electron donor and acceptor, resulting in significant enhancement
of short circuit current (<i>J</i><sub><i>sc</i></sub>) and fill factor (FF). The fluorination in the TPTQ unit reduced
the dipole moment of the D–A complex and gave a negative effect
on a polymer system. PFP showed worse electron accepting property
with lower electron mobility than PQP. It is reasoned that the internal
polarization plays an important role in the design of electron accepting
polymers. As a result, <b>PQP</b> having TPTQ monomer exhibited
the best photovoltaic performance with power conversion efficiency
(PCE) of 3.52% (<i>V</i><sub><i>oc</i></sub> =
0.71 V, <i>J</i><sub><i>sc</i></sub> = 8.57 mA/cm<sup>2</sup>, FF = 0.58) at a weight ratio of PTB7-Th:<b>PQP</b> = 1:1, under AM 1.5G
Propeller-Shaped Acceptors for High-Performance Non-Fullerene Solar Cells: Importance of the Rigidity of Molecular Geometry
This
paper describes the synthesis and application of βTPB6
and βTPB6-C as electron acceptors for organic solar cells. Compound
βTPB6 contains four covalently bonded PDIs with a BDT-Th core
at the β-position. The free rotation of PDIs renders βTPB6
with varying molecular geometries. The cyclization of βTPB6
yields βTPB6-C with high rigidity of the molecular geometry
and enlarged conjugated skeleton. The inverted solar cells based on
βTPB6-C and PTB7-Th as the donor polymer exhibited the highest
efficiency of 7.69% with <i>V</i><sub>oc</sub> of 0.92 V, <i>J</i><sub><i>sc</i></sub> of 14.9 mAcm<sup>–2</sup>, and FF of 0.56, which is 31% higher than that for βTPB6 based
devices. The larger fraction of βTPB6-C and PTB7-Th than that
of βTPB6:PTB7-Th in a blend film takes a face-on orientation
packing pattern for π-systems that benefits the charge transport
and hence higher PCE value than that for βTPB6:PTB7-Th. It was
also found that a proper DIO:DPE additive further enhances this trend,
which results in an increase of the PCE value for βTPB6-C:PTB7-Th
while decreasing the PCE value for βTPB6:PTB7-Th
Synthesis and Search for Design Principles of New Electron Accepting Polymers for All-Polymer Solar Cells
New electron withdrawing
monomers, thienoÂ[2′,3′:5′,6′]ÂpyridoÂ[3,4-<i>g</i>]ÂthienoÂ[3,2-<i>c</i>]Âisoquinoline-5,11Â(4<i>H</i>,10<i>H</i>)-dione (TPTI) and fluorenedicyclopentathiophene
dimalononitrile (CN), have been developed and used to form 12 alternating
polymers having different monomer combinations: (a) weak donating
monomer–strong accepting monomer, (b) weak accepting monomer–strong
accepting monomer, (c) weak accepting monomer–weak accepting
monomer, and (d) strong donating monomer–strong accepting monomer.
It was found that lowest unoccupied molecular orbital (LUMO) energy
levels of polymers are significantly determined by stronger electron
accepting monomers and highest occupied molecular orbital (HOMO) energy
levels by the weak electron accepting monomers. In addition, fluorescent
quantum yields of the TPTI-based polymers in chloroform solution are
significantly decreased as the LUMO energy levels of the TPTI series
of polymers become deeper. The quantum yield was found to be closely
related with the photovoltaic properties, which reflects the effect
of internal polarization on the photovoltaic properties. Only the
electron accepting polymers showing SCLC mobility higher than 10<sup>–4</sup> cm<sup>2</sup>/(V s) exhibited photovoltaic performance
in blend films with a donor polymer, and the PTB7:PNPDI (1:1.8 w/w)
device exhibited the highest power conversion efficiency of 1.03%
(<i>V</i><sub>oc</sub> = 0.69 V, <i>J</i><sub>sc</sub> = −4.13 mA/cm<sup>2</sup>, FF = 0.36) under AM 1.5G
condition, 100 W/cm<sup>2</sup>. We provide a large set of systematic
structure–property relationships, which gives new perspectives
for the design of electron accepting materials
Application of biochar derived from rice straw for the removal of Th(IV) from aqueous solution
<p>Biochar is increasingly used as a low-cost and effective adsorbent for heavy metals in wastewater. Herein, biochar pyrolyzed from rice straw was employed as an adsorbent for the removal of Th(IV) from aqueous solutions. The sorption of Th(IV) on biochar was strongly dependent on pH, but independent on ionic strength at pH < 6.4. The inner-sphere complexation dominated the sorption mechanism of Th(IV) on biochar. The competition for Th(IV) between aqueous or surface-adsorbed cations/anions and functional groups of biochar was pivotal for Th(IV) sorption. The thermodynamic data suggested that Th(IV) sorption was a spontaneous and endothermic process.</p