Surface doping of rubrene single crystals by molecular electron donors and acceptors Christos Gatsios 1 , Andreas Opitz 1 , Dominique Lungwitz 1 , Ahmed E. Mansour 2 , Thorsten Schultz 2 , Dongguen Shin 1 , Sebastian Hammer 3,4 , Jens Pflaum 3,5 , Yadong Zhang 6 , Stephen Barlow 6 , Seth R. Marder 6,7 and Norbert Koch 1,2 1 Humboldt Universität zu Berlin, Germany
2 Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany 3 Experimentelle Physik VI, Julius-Maximilians-Universität Würzburg, Germany 4 Center for Physics and Materials, McGill University, Montreal, Canada 5 Center for Applied Energy Research, Würzburg, Germany
6 Renewable and Sustainable Energy Institute (RASEI), University of Colorado Boulder, USA 7 Department of Chemical and Biological Engineering and Department of Chemistry, University of Colorado Boulder, USA The enhancement of organic semiconductor performance through surface molecular doping is a pivotal advancement for the development of organic electronic and optoelectronic devices. Rubrene, with its exceptional hole mobility, has emerged as a prime candidate for such applications, particularly within the realm of flexible organic electronics [1,2] . Successful realization of these devices, however, necessitates the strategic design of functional interfaces for achieving desired device characteristics. In this context, our study aims to understand the influence of surface molecular doping on the electronic band structure of single-crystal rubrene. Utilizing angle-resolved photoemission spectroscopy, we observe that the Fermi level shifts within the rubrene band gap, consistent with surface charge transfer due to the introduction of the dopant molecules. Interestingly, the valence band structure remains unperturbed, suggesting that surface transfer doping of single-crystal rubrene has the potential to control the charge density near the surface while preserving good charge carrier mobility. References 1. J. Takeya, M. Yamagishi, Y. Tominari, R. Hirahara, Y. Nakazawa, T. Nishikawa, T. Kawase, T. Shimoda, S. Ogawa, Appl. Phys. Lett. 2007 , 90 , 102120 2. A. L. Briseno, S. C. B. Mannsfeld, M. M. Ling, S. Liu, R. J. Tseng, C. Reese, M. E. Roberts, Y. Yang, F. Wudl, Z. Bao, Nat. 2006 4447121 2006 , 444 , 913.
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