Modulation of the Nonlinear Optical Properties of Dibenzo[<i>hi</i>,<i>st</i>]ovalene by Peripheral Substituents

Dibenzo­[hi,st]­ovalene (DBOV) is a nanographene molecule with quasi-zero dimensional electronic confinement that displays relatively high oscillator strength, remarkable photostability, and optical gain property. For these reasons, DBOV has been proposed as a gain medium and active material for achieving strong exciton-photon coupling in microcavities. Here, we study the stimulated emission properties of three DBOV derivatives with different substitution patterns. We found that these molecules likely undergo ultrafast intermolecular charge-transfer processes occurring within their π-aggregates, which ultimately leads to quenching of stimulated emission and increase of the amplified spontaneous emission threshold. These effects can be minimized by installing bulky substituents on the peripheries that prevent π–π stacking. Thus, by engineering the side groups, we can selectively favor either the luminescence/gain properties or the charge-transport features