Tuning ultrafast time‐evolution of photo‐induced charge‐transfer states: A real‐time electronic dynamics study in substituted indenotetracene derivatives

Abstract

Photo‐induced charge transfer (CT) states are pivotal in many technological and biological processes. A deeper knowledge of such states is mandatory for modeling the charge migration dynamics. Real‐time time‐dependent density functional theory (RT‐TD‐DFT) electronic dynamics simulations are employed to explicitly observe the electronic density time‐evolution upon photo‐excitation. Asymmetrically substituted indenotetracene molecules, given their potential application as n‐type semiconductors in organic photovoltaic materials, are here investigated. Effects of substituents with different electron‐donating characters are analyzed in terms of the overall electronic energy spacing and resulting ultrafast CT dynamics through linear response (LR‐)TD‐DFT and RT‐TD‐DFT based approaches. The combination of the computational techniques here employed provided direct access to the electronic density reorganization in time and to its spatial and rational representation in terms of molecular orbital occupation time evolution. Such results can be exploited to design peculiar directional charge dynamics, crucial when photoactive materials are used for light‐harvesting applications.

Key Role of Electronic and Structural Properties in Regulating Intersystem Crossing: An In-Depth Investigation on Naphthalene-Diimide Triads for Thermally Activated Delayed Fluorescence Applications

“…Naphthalene-diimides (1,4,5,8-naphthalenetetracarboxylic diimide, NDIs) are versatile polycyclic aromatic compounds showing reversible redox properties, chemical, thermal, and photochemical stability, good charge mobility with tunable electronic properties, and have attracted much attention due to their n-type semiconducting properties, making them excellent cases for studying electron transfer phenomena. − In the same fashion, the higher homologous perylene diimide dyes, due to their unique properties and enhanced solubility, are also actively researched in academia for organic electronics, energy-transfer processes, and dye lasers. − In particular, core-substituted NDIs are extremely attractive as building blocks for the synthesis of functional materials, and in recent years, NDIs have increasingly been used as pivotal molecular components for organic light-emitting diodes (OLEDs), − organic field-effect transistors, , photodynamic therapy, , and as chemical and biological sensors. − A variety of colorful OLEDs with desired hues have been synthesized, although it is still difficult to obtain efficient blue and stable red-emitting diodes. , In an OLED-based device, photons are emitted upon the recombination of excitons (a bound state of an electron and an electron hole), and when the excited state relaxes to the ground state, a process known as organic electroluminescence (EL) takes place. Exciton recombination can occur with four spin combinations; therefore, the spin statistics states that 25% of formed excitons are singlets and 75% are of triplet nature.…”