Long‐term instability and possible lead contamination are the two main issues limiting the widespread application of organic–inorganic lead halide perovskites. Here a facile and efficient solution‐phase method is demonstrated to synthesize lead‐free Cs2SnX6 (X = Br, I) with a well‐defined crystal structure, long‐term stability, and high yield. Based on the systematic experimental data and first‐principle simulation results, Cs2SnX6 displays excellent stability against moisture, light, and high temperature, which can be ascribed to the unique vacancy‐ordered defect‐variant structure, stable chemical compositions with Sn4+, as well as the lower formation enthalpy for Cs2SnX6. Additionally, photodetectors based on Cs2SnI6 are also fabricated, which show excellent performance and stability. This study provides very useful insights into the development of lead‐free double perovskites with high stability.

Portable and matured energy storage devices are in high demand for future flexible electronics. Flowery shaped MoS2 nanostructures with porous and flake like morphology was used to study the supercapacitive nature with specific capacitance (Csp) of 169.37F/g, the energy density of 28.43 Wh/Kg and power density of 10.18 W/Kg. This nanoflower like architecture was decorated on 3D-graphene on Graphite electrode to design the solid-state-supercapacitor prototype device of dimensions of 23.6 × 22.4 × 0.6 mm3 having considerable high Csp of 58.0F/g and energy density of 24.59 Wh/Kg, and power density of 8.8 W/Kg. Four fabricated supercapacitors were connected in series for real state practical demonstration using the light emitting diode that remains enlightened for 40 s by charging it only for 25 s. This study demonstrates the 3D-graphene/MoS2 nanohybrid has a quite high overall potential window nearly about 2.7 V (−1.5 to +1.2 V) in KOH-PVA medium which can be used for the development of solid-state supercapacitors thereby completely eliminating the need for any expensive ionic liquid mediums thus building an exciting potential for high-performance energy storage/transfer devices.

Vertically aligned carbon nanotubes (CNTs) have proven to be one of the best materials for use as an efficient field emitter. To further improve their efficiency as well as long-term use in practical devices, it is necessary to reduce the quantum resistance originating from the interface between electrode and emitters and the entanglement of the CNTs in a bundle texture. Thus, the incorporation of graphene at the bottom of CNT bundles via a seamless carbonaceous interface can easily solve this bottleneck. In this work we have demonstrated for the first time, growth and field emission properties of pure seamless graphene-CNT heterostructures and pure seamless graphene-vertically patterned oriented CNTs heterostructures (SGVCNTs) on Si/SiO2 substrates in contrast to the bare CNT mats and few-layer graphene structures without using any tedious post transfer processes. It was observed that seamless SGVCNTs show better field emission performance in terms of higher current density (236 mA cm−2), lowered turn-on field (0.45 V μm−1) and threshold field (1.931 V μm−1 @100 mA cm−2), and improved field enhancement factor (β ∼ 41 315) which is improved ∼4 fold when compared to a bare CNT mat. The significant improvement of the field emission performance of SGVCNTs is mainly attributed to the low resistive seamless C–C covalent carbonaceous interface, the higher number of emitter sites and patterned vertical orientation that leads to long-term stability of the field emitter with minimal loss up to 32 h. This finding could provide an important solution for carbonaceous material based field emitters for real phase device applications.

No abstract

No abstract