Tuning of the Electro-Optical Properties of Tetraphenylcyclopentadienone via Substitution of Oxygen with Sterically-Hindered Electron Withdrawing Groups.

In this report, the substitution of the oxygen group (=O) of Tetraphenylcyclopentadienone with =CR group (R = methyl ester or nitrile) was found to have tuned the electro-optical properties of the molecule. Although both groups are electrons withdrawing in nature, their absorption from UV-vis spectra analysis was observed to have been blue-shifted by methyl ester substitution and red-shifted by nitrile substitution. Interestingly, these substitutions helped to enhance the overall intensity of emission, especially in the context of methyl ester substitution whereby the emission was significantly boosted at higher concentrations due to hypothesized restrictions of intramolecular motions.

Origin of Extended UV Stability of 2D Atomic Layer Titania-Based Perovskite Solar Cells Unveiled by Ultrafast Spectroscopy.

The inherent instability of UV-induced degradation in TiO-based perovskite solar cells was largely improved by replacing the anatase-phase compact TiO layer with an atomic sheet transport layer (ASTL) of two-dimensional (2D) TiO. The vital role of microscopic carrier dynamics that govern the UV stability of perovskite solar cells was comprehensively examined in this work by performing time-resolved pump-probe spectroscopy. In conventional perovskite solar cells, the presence of a UV-active oxygen vacancy in compact TiO prohibits current generation by heavily trapping electrons after UV degradation.

Naphthobipyrrole-derived sapphyrins: rational synthesis, characterization, nonlinear optical properties, and excited-state dynamics.

Two new free-base β-octa and hexaalkyl naphthobipyrrole-derived sapphyrins are reported along with various salts thereof. One of them has substituents at all of its β positions, whereas the pyrrole unit opposite to the bipyrrolic moiety is unsubstituted in the other. The effect of bipyrrole fusion on the structure of sapphyrins was explored.