Response (on/off ratio) is one of the key parameters of ultraviolet (UV) sensors. In this paper, a kind of highly sensitive ZnO UV sensor with highly increased on/off current ratio was designed and developed. Under a weak UV intensity of 0.1 mW/cm 2 , this ultrathin ZnO film-based UV sensor has an on/off current ratio of 1.3 × 10 6 which is 3 times higher than the record value for ZnO-based UV sensors. In addition, it shows good flexibility and stable UV detection property during the bending process. When bending the sensor to a radius of curvature of about 18.5 mm, the sensor also shows high UV detection performance.
A flexible UV photodetector with a high on/off ratio is extremely important for environmental sensing, optical communication, and flexible optoelectronic devices. In this work, a flexible fiber-based UV photodetector with an ultrahigh on/off ratio is developed by utilizing the synergism between interface and surface gating effects on a ZnO nanowire network structure. The synergism between two gating effects is realized by the interplay between surface band bending and the Fermi level through the nanowire network structure, which is proved through the control experiments between the ZnO micro/nanowire photodetector and micro/nanowire junction photodetector, and the corresponding Kelvin probe force microscopy (KPFM) measurements. The on/off ratio of the fiber-based ZnO nanowire network UV photodetector reaches 1.98 × 10 8 when illuminated by 1.0 mW cm −2 UV light, which is 20 times larger than the largest reported result under the same UV illumination. This new UV sensor also has a high resolution to UV light intensity change in the nW cm −2 range. Furthermore, when the fiberbased photodetector is curved, it still shows excellent performance as above. This work gives a new effective route for the development of a high-performance UV photodetector or other optoelectronic detection devices.
Embedding silicon nanoparticles into carbon nanofibers is one of the effective methods to fabricate a self-standing and binder-free Si-based anode material for lithium-ion batteries. However, the sluggish Li-ion transport limits the electrochemical performance in the regular strategies, especially under high rate conditions. Herein, a kind of silicon nanoparticle in porous carbon nanofiber structures (Si/PCNFs) has been fabricated through a facile electrospinning and subsequent thermal treatment. By adjusting the mass ratio to 0.4:1, a Si/PCNF anode material with an effective Li + -migration pathway and excellent structural stability can be obtained, resulting in an optimal electrochemical performance. Although increasing the mass ratio of PEG to PAN further can lead to a larger pore size and can be beneficial to Li + migration, thus being profitable for the rate capacity, the structural stability will get worse at the same time as more defects will form and lead to a weaker C−C binding, thus decrease the cycling stability. Remarkably, the rate capacity reaches 1033.4 mA h g −1 at the current density of 5 A g −1 , and the cycling capacity is 933.2 mA h g −1 at 0.5 A g −1 after 200 cycles, maintaining a retention rate of 80.9% with an initial coulombic efficiency of 83.37%.
Poor
cycling stability and rate capability significantly limit the commercial
applications of silicon (Si) anode, due to the huge volume change
and poor electronic and ionic conductivity of Si. Combining Si with
SiO2 and carbon (C) can effectively improve the structural
stability of electrode, but common carbon coating still suffers from
the problem of comparatively low ionic conductivity. Here we designed
and developed a core–shell structural Si@SiO2@C/Se
anode with high ionic conductivity and structural stability by loading
selenium (Se) into a carbon framework. Remarkably, it exhibits a high
rate capability (612 mAh g–1 at 8 A g–1) and ultrahigh initial columbic efficiency (80.8%), which is much
higher than ordinary Si/SiO2-based anode (50–60%).
In addition, it shows an excellent cycling performance, which is about
1560 mAh g–1 after 150 charging/discharging cycles
at the current density of 0.5 A g–1. This work provides
a new technology to design high capacity alloy-type lithium-ion batteries
(LIBs) anode.
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