8 research outputs found
Cesium-Doped Vanadium Oxide as the Hole Extraction Layer for Efficient Perovskite Solar Cells
In this study, we report the utilization
of low-temperature solution-processed
Cs-doped VO<sub>X</sub> thin films as the hole extraction layers (HELs)
in perovskite solar cells (PSCs). It is found that the VO<sub>X</sub>:<i>y</i>Cs (where <i>y</i> is the mole ratio
of Cs versus V and <i>y</i> = 0.1, 0.3, and 0.5) thin films
possess better electrical conductivities than that of the pristine
VO<sub>X</sub> thin film. As a result, the PSCs incorporated with
the VO<sub>X</sub>:<i>y</i>Cs HEL exhibit large fill factors
and high short-circuit currents, with consequently high power conversion
efficiencies, which is more than 30% enhancement as compared with
pristine VO<sub>X</sub> HEL. Our studies provide a facial way to enhance
the electrical conductivity of the hole extraction layer for boosting
device performance of perovskite solar cells
Polyaniline-Modified Oriented Graphene Hydrogel Film as the Free-Standing Electrode for Flexible Solid-State Supercapacitors
In
this study, we report polyaniline (PANI)-modified oriented graphene
hydrogel (OGH) films as the free-standing electrode for flexible solid-state
supercapacitors (SCs). The OGH films are prepared by a facile filtration
method using chemically converted graphene sheets and then introduced
to PANI on the surface of OGH films by in situ chemical polymerization.
The PANI-modified OGH films possess high flexibility, high electrical
conductivity, and mechanical robustness. The flexible solid-state
SCs based on the PANI-modified OGH films exhibit a specific capacitance
of 530 F/g, keeping 80% of its original value up to 10 000
charge–discharge cycles at the current density of 10 A/g. Remarkably,
the flexible solid-state SCs maintain ∼100% capacitance retention
bent at 180° for 250 cycles. Moreover, the flexible solid-state
SCs are further demonstrated to be able to light up a red-light-emitting
diode. These results indicate that the flexible solid-state SCs based
on PANI-modified OGH films as the free-standing electrode have potential
applications as energy-storage devices
Comparative Study of Graphene Hydrogels and Aerogels Reveals the Important Role of Buried Water in Pollutant Adsorption
Water
as the universal solvent has well-demonstrated its ability
to dissolve many substances, but buried water inside different nanoporous
materials always exhibits some unusual behaviors. Herein, 3D porous
graphene hydrogel (GH) is developed as a super-adsorbent to remove
different pollutants (antibiotics, dyes, and heavy ions) for water
purification. Due to its highly porous structure and high content
of water, GH also demonstrated its super adsorption capacity for adsorbing
and removing different pollutants (antibiotics, dyes, and heavy ions)
as compared to conventional graphene aerogel (GA). More fundamentally,
the buried-water enhanced adsorption mechanism was proposed and demonstrated,
such that buried water in GH plays the combinatorial roles as (1)
supporting media, (2) transport nanochannels, and (3) hydrogen bondings
in promoting pollutant adsorption. In parallel, molecular dynamics
simulations further confirm that buried water in GH has the stronger
interaction with pollutants via hydrogen bonds than other buried alcohols.
GH integrates the merit of both graphene (e.g., fine chemical resistance
and excellent mechanical property) and hydrogel (e.g., high water
content, porous structure, and simple solution-based processability
and scalability), giving it promising potential for environmental
applications
Ni<sub>0.85</sub>Se@MoSe<sub>2</sub> Nanosheet Arrays as the Electrode for High-Performance Supercapacitors
In this study, we report novel Ni<sub>0.85</sub>Se@MoSe<sub>2</sub> nanosheet arrays prepared by a facile
one-step hydrothermal method
through nickel (Ni) foam as Ni precursor and the framework of MoSe<sub>2</sub>. Owing to the unique interconnection and hierarchical porous
nanosheet array architecture, the Ni<sub>0.85</sub>Se@MoSe<sub>2</sub> nanosheet arrays exhibit a high specific capacitance of 774 F g<sup>–1</sup> at the current density of 1 A g<sup>–1</sup>, which is almost 2 times higher than that (401 F g<sup>–1</sup>) of the Ni<sub>0.85</sub>Se matrix and about 7 times greater than
that (113 F g<sup>–1</sup>) of the MoSe<sub>2</sub> nanoparticles.
Moreover, we report an asymmetric supercapacitor (ASC), which is fabricated
by using the Ni<sub>0.85</sub>Se@MoSe<sub>2</sub> nanosheet arrays
as the positive electrode and the graphene nanosheets (GNS) as the
negative electrode, with aqueous KOH as the electrolyte. The Ni<sub>0.85</sub>Se@MoSe<sub>2</sub>//GNS ASC possesses an output voltage
of 1.6 V, an energy density of 25.5 Wh kg<sup>–1</sup> at a
power density of 420 W kg<sup>–1</sup>, and a cycling stability
of 88% capacitance retention after 5000 cycles. These results indicate
that the Ni<sub>0.85</sub>Se@MoSe<sub>2</sub> nanosheet arrays are
a good electrode for supercapacitors
Synthesis of Anthracene-Based Donor–Acceptor Copolymers with a Thermally Removable Group for Polymer Solar Cells
A highly
soluble anthracene cyclic adduct with a thermally cleavable substituent
was synthesized, and it was used as a donor unit in a series of donor–acceptor
type conjugated copolymers with improved processability. The removable
group was eliminated under elevated temperature through retro Diels–Alder
reaction, which offered the corresponding copolymers with better planarity
and rigidity. Thermogravimetric analysis (TGA), FT-IR, and UV–vis
spectroscopy were carried out to study the thermal cleavage process.
Uniform films were easily formed from these precursor copolymers due
to their good solution processabilty. Polymer solar cells were successfully
fabricated through applying thermal annealing treatment on the blend
films that were spin-coated from solutions of the precursor copolymers
blended with fullerene derivatives. The best polymer solar cell device
with a power conversion efficiency (PCE) of 2.15% was achieved based
on copolymer PCOAEHDPP
Enhanced Thermoelectric Properties of Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) by Binary Secondary Dopants
To simultaneously increase the electrical
conductivity and Seebeck coefficient of polyÂ(3,4-ethylenedioxythiophene):polystyrenesulfonate
(PEDOT:PSS) was a challenge for realizing efficient organic thermoelectrics.
In this study, for the first time, we report both increased electrical
conductivities and Seebeck coefficients, hence, enhanced thermoelectric
properties of PEDOT:PSS thin films by doped with binary secondary
dopants, dimethyl sulfoxide (DMSO) and polyÂ(ethylene oxide) (PEO).
Without modifying film morphology, the molar ratios of PEDOT to PSS
are tuned by PEO, resulting in increased proportions of PEDOT in the
bipolaron states. Our study provides a facile route to optimizing
thermoelectric properties of PEDOT:PSS thin films
Efficient Polymer Solar Cells by Lithium Sulfonated Polystyrene as a Charge Transport Interfacial Layer
In this paper, we
report the highly efficient bulk heterojunction (BHJ) polymer solar
cells (PSCs) with an inverted device structure via utilizing an ultrathin
layer of lithium sulfonated polystyrene (LiSPS) ionomer to reengineer
the surface of the solution-processed zinc oxide (ZnO) electron extraction
layer (EEL). The unique lithium-ionic conductive LiSPS contributes
to enhanced electrical conductivity of the ZnO/LiSPS EEL, which not
only facilitates charge extraction from the BHJ active layer but also
minimizes the energy loss within the charge transport processes. In
addition, the organic–inorganic LiSPS ionomer well circumvents
the coherence issue of the organic BHJ photoactive layer on the ZnO
EEL. Consequently, the enhanced charge transport and the lowered internal
resistance between the BHJ photoactive layer and the ZnO/LiSPS EEL
give rise to a dramatically reduced dark saturation current density
and significantly minimized charge carrier recombination. As a result, the inverted BHJ PSCs
with the ZnO/LiSPS EEL exhibit an approximatively 25% increase in
power conversion efficiency. These results indicate our strategy provides
an easy, but effective, approach to reach high performance inverted
PSCs
Understanding the Halogenation Effects in Diketopyrrolopyrrole-Based Small Molecule Photovoltaics
Two molecules containing a central
diketopyrrolopyrrole and two oligothiophene units have been designed
and synthesized. Comparisons between the molecules containing terminal
F (FDPP) and Cl (CDPP) atoms allowed us to evaluate the effects of
halogenation on the photovoltaic properties of the small molecule
organic solar cells (OSCs). The OSCs devices employing FDPP:PC<sub>71</sub>BM films showed power conversion efficiencies up to 4.32%,
suggesting that fluorination is an efficient method for constructing
small molecules for OSCs