Berlin 2015 – scientific programme
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DS: Fachverband Dünne Schichten
DS 1: Organic Electronics and Photovoltaics
DS 1.5: Talk
Monday, March 16, 2015, 10:30–10:45, H 2032
Photoelectron spectroscopy studies on efficient air-stable molecular n-dopants — •Martin Schwarze1, Max L. Tietze1, Paul Pahner1, Ben Naab2, Zhenan Bao2, Björn Lüssem1, Daniel Kasemann1, and Karl Leo1 — 1Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden, Germany — 2Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States
Understanding the working mechanism of electrical doping in organic semiconductors is essential for the optimization of organic semiconductor devices such as organic light emitting diodes or organic solar cells. A defined doping concentration allows for the control of the Fermi-level position as well as the adjustment of the conductivity of transport layers. In comparison to molecular p-doping of organic semiconductors, n-doping creates the additional problem of air instability. To successfully transfer an electron to the lowest unoccupied molecular orbital (LUMO) of the matrix material, dopants exhibiting shallow highest molecular orbitals (HOMO) are necessary, rendering them prone to reactions with e.g. oxygen. In this study, three different types of n-dopants are compared: air stable cationic DMBI dopants, halogen-free DMBI dimers, and the established but air sensitive Cr2(hpp)4. Fermi-level shift and conductivity of co-evaporated Bis-HFl-NTCDI layers at different doping concentrations as well as stability during air exposure are investigated by UPS and electrical measurements.