The interface electronic properties of organic photovoltaic cells

Autor: Norbert Koch, Patrick Amsalem, Georg Heimel, Martin Oehzelt
Rok vydání: 2015
Předmět:
Zdroj: Journal of Electron Spectroscopy and Related Phenomena. 204:177-185
ISSN: 0368-2048
DOI: 10.1016/j.elspec.2015.02.012
Popis: The electronic properties of interfaces play a decisive role in determining the electrical characteristics of organic photovoltaic cells. In this paper, it is proposed that the mechanism responsible for the energy level alignment observed upon interface formation involves charge transfer between the electrode and the organic semiconductor. The amount of charges transferred is determined by occupying the density of states of the semiconductor according to Fermi–Dirac statistics and the observed energy level shifts are then governed by electrostatics. Within the proposed framework, we also discuss and numerically model the impact of the coupling strength between the molecular and the metal states. Photoelectron spectroscopy studies on two types of technologically relevant model interfaces, namely a metal/insulator/organic semiconductor heterojunction and a donor/acceptor heterojunction supported on a metal electrode, are then presented. The experimental observations, ranging from band bending to interface dipole formation, are shown to emerge naturally from the same theoretical framework. These results unambiguously demonstrate the essential role of the metal electrode in governing the energy level alignment, even significantly away from the metal surface.
Databáze: OpenAIRE
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