For the first time, large-area CVD-grown graphene films transferred onto flexible PET substrates were used as transparent conductive electrodes in alternating current electroluminescence (ACEL) devices. The flexible ACEL device based on a single-layer graphene electrode has a turn-on voltage of 80 V; at 480 V (16 kHz), the luminance and luminous efficiency are 1140 cd/m(2) and 5.0 lm/W, respectively. The turn-on voltage increases and the luminance decreases with increasing stacked layers of graphene, which means the single-layer graphene is the best optimal choice as the transparent conductive electrode. Furthermore, it demonstrates that the graphene-based ACEL device is highly flexible and can work very well even under a very large strain of 5.4%, suggesting great potential applications in flexible optoelectronics.
For the first time, large-area, vertically oriented few-layered hafnium disulfide (V-HfS 2 ) nanosheets have been grown by chemical vapor deposition. The individual HfS 2 nanosheets are well [001] oriented, with highly crystalline quality. Far different from conventional van der Waals epitaxial growth mechanism for two-dimensional transition metal dichalcogenides, a novel dangling-bondassisted self-seeding growth mechanism is proposed to describe the growth of V-HfS 2 nanosheets: difficult migration of HfS 2 adatoms on substrate surface results in HfS 2 seeds growing perpendicularly to the substrate; V-HfS 2 nanosheets inherit the growth direction of HfS 2 seeds; V-HfS 2 nanosheets further expand in the in-plane direction with time evolution. Moreover, the V-HfS 2 nanosheets show strong and broadened photons absorption from near infrared to ultraviolet; the V-HfS 2 -based photodetector exhibits an ultrafast photoresponse time of 24 ms, and a high photosensitivity ca. 10 3 for 405 nm laser.
A facile method was presented to synthesize three-dimensional carbon nanotubes/graphene-sulfur (3DCGS) sponge with high sulfur loading of 80.1%. In the well-designed 3D architecture, the two-dimensional graphene nanosheets functions as the 3D porous backbone and the one-dimensional (1D) highly conductive carbon nanotubes (CNT) can not only significantly enhance the conductivity, but also effectively tune the mesopore structure. Compared to the three-dimensional graphene-sulfur (3DGS) sponge without CNT, the conductivity of 3DCGS is enhanced by 324.7%; most importantly, compared to the monomodal mesopores (with a size of 3.5 nm) formed in the 3DG, the bimodal mesopores (with sizes of 3.5 and 32.1 nm) were formed in 3DCG; the bimodal mesopores, especially the newly formed 32.1-nm mesopores, provide abundant electrochemical nanoreactors, accommodate plenty of sulfur and polysulfides, and facilitate the charge transportation and electrolyte penetration. The significantly enhanced conductivity and the unique bimodal-mesopore structure in 3DCGS, result in its superior electrochemical performance. The reversible discharge capacity for sulfur is 1217 mAh g -1 ; corresponding capacity for the whole electrode (including the 3DCGS, the conductive additive and the binder) is 877.4 mAh g ିଵ , which is the highest ever reported. In addition, the capacity decay is as low as 0.08% per cycle, and the high-rate capacity up to 4 C is as large as 653.4 mAh g -1 . The 3DCGS sponge with high sulfur loading is promising as superior-capacity cathode for lithium-sulfur batteries.
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