The rapid development of portable/wearable electronics proposes new demands for energy storage devices, which are flexibility, smart functions and long-time outdoor operation. Supercapacitors (SCs) ...show great potential in portable/wearable applications, and the recently developed flexible, smart and self-sustainable supercapacitors greatly meet the above demands. In these supercapacitors, conductive polymers (CPs) are widely applied due to their high flexibility, conductivity, pseudo-capacitance, smart characteristics and moderate preparation conditions. Herein, we'd like to introduce the CP-based flexible, smart and self-sustainable supercapacitors for portable/wearable electronics. This review first summarizes the flexible SCs based on CPs and their composites with carbon materials and metal compounds. The smart supercapacitors,
i.e.
, electrochromic, electrochemical actuated, stretchable, self-healing and stimuli-sensitive ones, are then presented. The self-sustainable SCs which integrate SC units with energy-harvesting units in one compact configuration are also introduced. The last section highlights some current challenges and future perspectives of this thriving field.
Progress of utilizing conductive polymers and their composites to prepare flexible, smart and self-sustainable supercapacitors for portable/wearable electronics is reviewed.
When the in vitro research works of biosensing begin to mimic in vivo conditions, some certain three-dimensional (3D) structures of biosensors are needed to accommodate biomolecules, bacteria or even ...cells to resemble the in vivo 3D environment. To meet this end, a novel method of synthesizing CuO nanoflowers on the 3D graphene foam (GF) was first demonstrated. The 3DGF/CuO nanoflowers composite was used as a monolithic free-standing 3D biosensor for electrochemical detection of ascorbic acid (AA). The 3D conductive structure of the GF is favorable for current collection, mass transport and loading bioactive chemicals. And CuO nanoflowers further increase the active surface area and catalyze the redox of AA. Thus, all these features endows 3DGF/CuO composite with outstanding biosensing properties such as an ultrahigh sensitivity of 2.06mAmM−1cm−2 to AA at 3s response time.
•The synthesis of 3D graphene foam (GF)/CuO nanoflowers composite was proposed.•The 3DGF provides vast area and a well-organized conducting freestanding network.•CuO nanoflowers maximize the surface area, transfer electrons between 3DGF and AA.•3DGF/CuO has an ultrahigh sensitivity of 2.06mAmM−1cm−2 to AA.•3DGF/CuO could be a smart sensing platform to support cells and detect analytes.
All-inorganic lead halide perovskite quantum dots (CsPbBr3 QDs) are attracting significant research interests because of their highly efficient light-emitting performance combined with tunable ...emission wavelength facilely realized by ion exchange. However, blue emission from perovskite QDs with strong quantum confinement is rarely reported and suffers from lower luminescence efficiency. Here we report blue-emitting ultrasmall (∼3 nm) CsPbBr3 QDs with photoluminescence (PL) quantum yield as high as 68%. Using time-resolved and steady-state PL spectroscopy, we elucidate the mechanism of the highly efficient PL as recombination of excitons localized in radiative band tail states. Through analyzing the spectral-dependent PL lifetime and the PL line shape, we obtain a large band tail width of ∼80 meV and a high density of state of ∼1020 cm–3. The relaxation of photocarriers into the radiative tail states suppresses the capture by nonradiative centers. Our results provide solid evidence for the positive role of band tail states in the optical properties of lead halide perovskites, which can be further tailored for high-performance optoelectronic devices.
Here, we present a facile technique to design self-supported 3D N-doped graphene foam (NGF) via simply annealing in chemical vapor deposition furnace which used powder metallurgy nickel template and ...melamine as both carbon and nitrogen source. The NGF possesses highly conductive and interconnected mesoporous network. Particularly nitrogen-doping provided strong polysulfide immobilization ability, significantly suppressing the shuttle effect. The NGF was directly used as binder-free electrode which delivered a high initial discharge capacity of 987 mA h g−1 and maintains at 819 mA h g−1 after 200 cycles at 0.2 C, corresponding to 82.9% capacity retention. Specifically, even at high current density of 2 C, it still possesses a good long life cycle performance (from 633.8 mA h g−1 to 440.3 mA h g−1 after 500 cycles, with ultralow capacity fading rate of 0.061% per cycle). 7Li nuclear magnetic resonance (7Li NMR) suggested strong interaction between NGF and polysulfide. Moreover, X-ray photoelectron spectroscopy and density function theory calculation further revealed the strong interaction mostly ascribed to chemisorption and physisorption of polysulfide by pyridinic and pyrrolic nitrogen, respectively. As we know this method-based NGF as binder free electrode was first reported, which provided an effective strategy for developing high-performance Li/S batteries.
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Fundamental to understanding and predicting the optoelectronic properties of semiconductors is the basic parameters of excitons such as oscillator strength and exciton binding energy. However, such ...knowledge of CsPbBr3 perovskite, a promising optoelectronic material, is still unexplored. Here we demonstrate that quasi-two-dimensional (quasi-2D) CsPbBr3 nanoplatelets (NPLs) with 2D exciton behaviors serve as an ideal system for the determination of these parameters. It is found that the oscillator strength of CsPbBr3 NPLs is up to 1.18 × 104, higher than that of colloidal II–VI NPLs and epitaxial quantum wells. Furthermore, the exciton binding energy is determined to be of ∼120 meV from either the optical absorption or the photoluminescence analysis, comparable to that reported in colloidal II–VI quantum wells. Our work provides physical understanding of the observed excellent optical properties of CsPbBr3 nanocrystals and would benefit the prediction of high-performance excitonic devices based on such materials.
High‐performance perovskite light‐emitting diodes are achieved by an interfacial engineering approach, leading to the most efficient near‐infrared devices produced using solution‐processed emitters ...and efficient green devices at high brightness conditions.
In this work, β-Ga
2
O
3
thin films were deposited by pulsed laser deposition (PLD) with changing oxygen pressure in the chamber. The
θ
–2
θ
scan x-ray diffraction (XRD) results reveal that the ...quality of the thin film obviously deteriorates when the oxygen pressure is greater than 0.1 Pa. Photoluminescence (PL) spectra measured at room temperature show that the major emission band can be separated into three Gaussian bands at about 370 nm (∼3.34 eV), 410 nm (∼3.03 eV), and 453 nm (∼2.74 eV), respectively. Using this analysis combined with x-ray photoelectron spectroscopy (XPS), we found that the three luminescence peaks originate from a self-trapped hole (STH) (between two OII-s sites), (
V
Ga
+
V
O
)
1−
and
V
G
a
2
-
(tetrahedral site), respectively. This work provides us a way to tune the emission of β-Ga
2
O
3
thin films.
Colloidal metal oxide nanocrystals offer a unique combination of excellent low-temperature solution processability, rich and tuneable optoelectronic properties and intrinsic stability, which makes ...them an ideal class of materials as charge transporting layers in solution-processed light-emitting diodes and solar cells. Developing new material chemistry and custom-tailoring processing and properties of charge transporting layers based on oxide nanocrystals hold the key to boosting the efficiency and lifetime of all-solution-processed light-emitting diodes and solar cells, and thereby realizing an unprecedented generation of high-performance, low-cost, large-area and flexible optoelectronic devices. This review aims to bridge two research fields, chemistry of colloidal oxide nanocrystals and interfacial engineering of optoelectronic devices, focusing on the relationship between chemistry of colloidal oxide nanocrystals, processing and properties of charge transporting layers and device performance. Synthetic chemistry of colloidal oxide nanocrystals, ligand chemistry that may be applied to colloidal oxide nanocrystals and chemistry associated with post-deposition treatments are discussed to highlight the ability of optimizing processing and optoelectronic properties of charge transporting layers. Selected examples of solution-processed solar cells and light-emitting diodes with oxide-nanocrystal charge transporting layers are examined. The emphasis is placed on the correlation between the properties of oxide-nanocrystal charge transporting layers and device performance. Finally, three major challenges that need to be addressed in the future are outlined. We anticipate that this review will spur new material design and simulate new chemistry for colloidal oxide nanocrystals, leading to charge transporting layers and solution-processed optoelectronic devices beyond the state-of-the-art.
This review bridges the chemistry of colloidal oxide nanocrystals and their application as charge transporting interlayers in solution-processed optoelectronics.
Organolead trihalide perovskites have attracted great attention due to the stunning advances in both photovoltaic and light-emitting devices. However, the photophysical properties, especially the ...recombination dynamics of photogenerated carriers, of this class of materials are controversial. Here we report that under an excitation level close to the working regime of solar cells, the recombination of photogenerated carriers in solution-processed methylammonium-lead-halide films is dominated by excitons weakly localized in band tail states. This scenario is evidenced by experiments of spectral-dependent luminescence decay, excitation density-dependent luminescence and frequency-dependent terahertz photoconductivity. The exciton localization effect is found to be general for several solution-processed hybrid perovskite films prepared by different methods. Our results provide insights into the charge transport and recombination mechanism in perovskite films and help to unravel their potential for high-performance optoelectronic devices.
•The ingenious GOx/p-NiO/n-Bi4Ti3O12 sandwich structure prevents the leakage of enzyme effectively.•A desirable nanostructure of p-n heterojunction contributes to the efficient separation of ...electron-hole pairs.•Co-catalysis of GOx and p-NiO/n-Bi4Ti3O12 heterojunctio plays a synergetic role in gaining performance boosts.•The novel biosensor remedies the limitation of enzyme-based glucose sensor due to its ultrahigh sensitivity.
A glucose oxidase (GOx) based p-NiO/n-Bi4Ti3O12 sandwich heterojunction was fabricated and explored as a glucose electrochemical sensor. The constructed GOx/p-NiO/n-Bi4Ti3O12 sandwich structure effectively prevents the leakage of GOx. Dandelion-like Bi4Ti3O12 nanowires were directly grown on the titanium foil substrates, and dense NiO nanoparticles were deposited by employing pulsed laser deposition at room temperature. Amperometric measurements towards glucose were carried out, and efficient direct electron transfer was successfully achieved. The enzyme biosensor showed a linear range from 20 μM to 3.55 mM (R = 0.999) with an ultrahigh sensitivity of 215 μA mM−1 cm−2, response time within 2 s, low detection limit of 1.26 μM (S/N = 3) and high specificity. The apparent Michaelis-Menten constant (Km app) was estimated to be 0.22 mM. Intercrossed nanowires and interconnected pores favor the electrons transfer and the massive GOx loading. Binder-free feature leads to a seamless connection between Bi4Ti3O12 nanowires and the substrate. Co-catalysis of GOx and p-NiO/n-Bi4Ti3O12 heterojunction plays a synergetic role in gaining performance boosts. The GOx based p-NiO/n-Bi4Ti3O12 heterojunction biosensor remedies the limitation of enzyme-based glucose sensor and be potentially applied in practice.
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