David Beljonne

Modeling the electronic structure at organic interfaces: From small molecules to hybrid perovskites

Over the last decade, the Mons group has been very active in setting up a multifaceted modeling framework that implements classical nuclear motion and electronic polarization effects together with quantum electronic and electron-phonon interactions, maps these first-principles results onto model Hamiltonians and solves their time evolution using mixed quantum-classical simulations. Here, we would like to review some recent applications of this theoretical methodology with a special emphasis on the role of charge-transfer or charge-resonance excitations at the ‘interface’ with organics. The wording ‘interface’ will be considered in the broadest possible scope, as we will deal with:

• Intramolecular charge transfer excitations in donor-acceptor molecular dyes used for thermally activated delayed emission;
• Intermolecular charge transfer excitations at organic-organic heterojunctions and their role for charge photogeneration in solar cell applications;
• Intermolecular charge resonance excitations in organic molecular crystals and their impact on optical properties and singlet fission;

If time permits, we will then extend the scope of the talk to bulk hybrid organic-inorganic perovskites and their interfaces with small molecules, highlighting similarities with organics, namely on the role of electrostatics, point defects and electron-phonon interactions.