Interface dipole at organic/metal interfaces and organic solar cells

In organic-based solar cells, the interface dipole present at the organic/metal interface participates to the collection and injection of charges between the electrode and the active organic material. The origins of the interface dipole is illustrated for a model system of the organic/metal interface composed of the electron–donor molecule p-phenylenediamine (PPDA) interacting with a nickel surface. The interface dipole created at the PPDA/Ni interface is characterized in a joint experimental and theoretical study using photoelectron spectroscopy and density functional theory calculations. The formation of strong interface dipoles upon chemisorption of a PPDA mono-layer is accompanied by a significant decrease (1.5 eV) of the metal work function reaching 3.6 eV.