RESUMEN
Structural distortion in halide perovskites is important to tune the optical properties of the materials. The octahedra formed by metal cations and halide anions in these classes of materials remain symmetric; however, the introduction of asymmetry provides enormous opportunities to improve the photoluminescence emission and excited-state lifetimes for their application in white light emitters. In this work, we have systematically introduced asymmetry in vacancy-ordered halide triple perovskite materials Cs3M2X9 (M = Bi3+, Sb3+; X = Cl-, Br-, I-) by mixing trivalent sites in three different halide compounds. The Raman and FT-far-IR measurements were used to investigate the distortion introduced in these materials. The distortion is shown to (i) enhance self-trapped excitonic emission, which is broad and intense leading to emission in the complete visible region and (ii) improve excited-state lifetimes. This strategy to create distortion and its proven ability to improve light emission will find application in light-emitting diodes.
RESUMEN
Electrochemical anodized titanium dioxide (TiO2) nanotubes are of immense significance as electrochemical energy storage devices owing to their fast electron transfer by reducing the diffusion path and paving way to fabricating binder-free and carbon-free electrodes. Besides these advantages, when nitrogen is doped into its lattice, doubles its electrochemical activity due to enhanced charge transfer induced by oxygen vacancy. Herein, we synthesized nitrogen-doped TiO2 (N-TiO2) and studied its electrochemical performances in supercapacitor and as anode for a lithium-ion battery (LIB). Nitrogen doping into TiO2 was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical performance of N-TiO2 nanotubes was outstanding with a specific capacitance of 835 µF cm-2 at 100 mV s-1 scan rate as a supercapacitor electrode, and it delivered an areal discharge capacity of 975 µA h cm-2 as an anode material for LIB which is far superior to bare TiO2 nanotubes (505 µF cm-2 and 86 µA h cm-2, respectively). This tailor-made nitrogen-doped nanostructured electrode offers great promise as next-generation energy storage electrode material.