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Herein, a phenomenological rule is presented for the estimation of electronic contact properties of organic–organic and inorganic–organic hetero interfaces, which is deduced from a large number of experimentally studied heterojunctions. The data for the present study are summarized from in situ step‐by‐step interface experiments using photoelectron spectroscopy. Organic and inorganic (oxide) materials are investigated which are used for the manufacturing of organic based optoelectronic devices in the InnovationLab Heidelberg. It is shown that the measured values of the interface dipole as well as of the band bending linearly depend on the work function difference between substrate and adsorbate. The data suggest that the investigated materials as technologically applied films contain a prototypical concentration of electron states at the interface and in the bulk, the charge of which is adjusted to reach thermodynamic equilibrium at a contact. As a consequence, a generally applicable empirical formula to predict the energetic band alignment due to dipole formation and the contact potential distribution due to band bending can be deduced, which is given by just the work function differences between the pristine layers. This result suggests that band bending as well as interface dipole formation are both attained by redistribution of electronic charge via integer charge transfer processes. [ABSTRACT FROM AUTHOR]

We study the evolution of the electric surface potential for small molecular organic semiconductors adsorbed on different high-work function substrates using photoelectron spectroscopy. Usually, the surface potential of these materials shows a typical progression in dependence of the adsorbate layer thickness indicating the formation of a space charge region near the interface. We discuss the surface potential evolution on the basis of the commonly used Schottky model and a second model using a density of states distribution (DOS) in the adsorbed semiconductor energy gap. In order to derive an analytical solution, we simplify an existing approach for space charge regions at polymer contacts. This approach is based on tailing gap states in polymer adsorbates. We simplify it using a constant DOS distribution. The differences between the Schottky model and the simplified distributed states model will be discussed. Finally, both models are applied to measured values of the surface potential evolution of some exemplary organic molecules on different substrates. We find that the surface potential evolution of the simplified distributed states model describes the measured potential development more accurately than the Schottky model. The DOS is estimated in the framework of the model being between 1018 and 1019 cm−3 eV−1. [ABSTRACT FROM AUTHOR]