Photo-Induced Doping in Graphene/Silicon Heterostructures

Photoinduced doping in graphene and its related heterostructures has drawn much interest as one of the possible ways to control the electronic properties of graphene. In this paper, we report that graphene/silicon (Gr/Si) heterostructures are an effective configuration for photoinduced doping in graphene. Raman spectroscopy, electrical and photoelectrical measurements are used to characterize the photoinduced doping effect. The results demonstrate that the graphene in the Gr/Si heterostructure is <i>p</i>-doped by light irradiation, and the doping effect can be controlled by varying the irradiation time. For the electrical properties of the Gr/Si Schottky junction, the photoinduced doping effect reduces the barrier height and series resistance but enhances the ideality factor. For the photovoltaic properties, the doping strengthens the open-circuit voltage, short-circuit current, fill factor, and conversion efficiency. The work should be helpful on developing effective ways for graphene doping and in depth understanding and better use of Gr/Si Schottky junctions for electronics and optoelectronics

Wrapping Aligned Carbon Nanotube Composite Sheets around Vanadium Nitride Nanowire Arrays for Asymmetric Coaxial Fiber-Shaped Supercapacitors with Ultrahigh Energy Density

The emergence of fiber-shaped supercapacitors (FSSs) has led to a revolution in portable and wearable electronic devices. However, obtaining high energy density FSSs for practical applications is still a key challenge. This article exhibits a facile and effective approach to directly grow well-aligned three-dimensional vanadium nitride (VN) nanowire arrays (NWAs) on carbon nanotube (CNT) fiber with an ultrahigh specific capacitance of 715 mF/cm² in a three-electrode system. Benefiting from their intriguing structural features, we successfully fabricated a prototype asymmetric coaxial FSS (ACFSS) with a maximum operating voltage of 1.8 V. From core to shell, this ACFSS consists of a CNT fiber core coated with VN@C NWAs as the negative electrode, Na₂SO₄ poly­(vinyl alcohol) (PVA) as the solid electrolyte, and MnO₂/conducting polymer/CNT sheets as the positive electrode. The novel coaxial architecture not only fully enables utilization of the effective surface area and decreases the contact resistance between the two electrodes but also, more importantly, provides a short pathway for the ultrafast transport of axial electrons and ions. The electrochemical results show that the optimized ACFSS exhibits a remarkable specific capacitance of 213.5 mF/cm² and an exceptional energy density of 96.07 μWh/cm², the highest areal capacitance and areal energy density yet reported in FSSs. Furthermore, the device possesses excellent flexibility in that its capacitance retention reaches 96.8% after bending 5000 times, which further allows it to be woven into flexible electronic clothes with conventional weaving techniques. Therefore, the asymmetric coaxial architectural design allows new opportunities to fabricate high-performance flexible FSSs for future portable and wearable electronic devices

Vanadium Dioxide Nanosheets Supported on Carbonized Cotton Fabric as Bifunctional Textiles for Flexible Pressure Sensors and Zinc-Ion Batteries

Flexible pressure sensors and aqueous batteries have been widely used in the rapid development of wearable electronics. The synergistic functionalities of versatile materials with multidimensional architectures are recognized to have a significant impact on the performance of flexible electronics. Herein, a facile hydrothermal strategy was demonstrated to conformally grow vanadium dioxide nanosheets on carbonized cotton fabrics (VO2/CCotton), which is a candidate material used in flexible piezoresistive sensors. As a result, the VO2/CCotton-based pressure sensor behaved with high sensitivity (S = 7.12 kPa–1 in the pressure range of 0–2.0 kPa) and a stable sensing ability in a wide pressure scale of 0–120 kPa. Further practical applications were performed in monitoring delicate physiological signals as well, such as twisting, blowing, and voice vibration recognitions. In addition, another application for energy storage was investigated as well. A quasi-solid-state aqueous zinc-ion battery was assembled with VO2/CCotton as the cathode and a film of Zn nanosheets/carbon nanotube as the anode. A capacity as high as 301.5 mAh g–1 and remarkable durability of 88.7% capacity retention after 5000 cycles at 10 A g–1 were found. These exceptional outcomes are attributed to the unique three-dimensional architecture and the prominent synergetic effects of CCotton and VO2 and allow for the proposal of novel guidelines for next-generation multifunctional flexible electronics