A-site composition tuning in methylammonium-based metal halide perovskite colloidal nanocrystals.

Utilizing the soft-lattice nature of metal halide perovskites, we employ post-synthetic cross-ion exchange to synthesize a series of narrow band-gap colloidal nanocrystals of methylammonium-based lead iodide solid solutions of composition FAMAPbI, as well as those of triple-cation composition CsFAMAPbI (TCPbI). The ability to finely tune the compositions not only helps in tailoring the optical properties in the near-infrared region, but also improves the stability of these colloidal nanocrystals towards moisture, which has been demonstrated as compared to their bulk counterparts. The thermal stability of these solid solutions is also comparable to that of the bulk, as evidenced by thermogravimetric studies.

Theoretical analysis of large negative dispersion photonic crystal fiber with small confinement loss.

Solid core circular and octagonal photonic crystal fibers (CPCF and OPCF) are proposed for analyzing different guiding properties such as dispersion, effective mode area, nonlinearity, and confinement loss from 0.8 to 2.6 µm wavelength.