Pentacene Excitons in Strong Electric Fields. Issue 3 (15th January 2018)

• Record Type: Journal Article
• Authors: Kuhnke, Klaus; Turkowski, Volodymyr; Kabakchiev, Alexander; Lutz, Theresa; Rahman, Talat S.; Kern, Klaus
• Is Part Of: Chemphyschem. Volume 19:Issue 3(2018)
• Page Start: 277
• Page End: 283
• Publication Date: 2018-01-15
• Subjects: density functional calculations -- electroluminescence -- excitons -- pentacene -- scanning probe microscopy; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201701174
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: Electroluminescence spectroscopy of organic semiconductors in the junction of a scanning tunneling microscope (STM) provides access to the polarizability of neutral excited states in a well‐characterized molecular geometry. We study the Stark shift of the self‐trapped lowest singlet exciton at 1.6 eV in a pentacene nanocrystal. Combination of density functional theory (DFT) and time‐dependent DFT (TDDFT) with experiment allows for assignment of the observation to a charge‐transfer (CT) exciton. Its charge separation is perpendicular to the applied field, as the measured polarizability is moderate and the electric field in the STM junction is strong enough to dissociate a CT exciton polarized parallel to the applied field. The calculated electric‐field‐induced anisotropy of the exciton potential energy surface will also be of relevance to photovoltaic applications. Abstract : In Stark resolution : Electroluminescence spectroscopy of organic semiconductors in the junction of a scanning tunneling microscope (STM) provides access to the polarizability of neutral excited states in a well‐characterized molecular geometry. The Stark shift of excitons in a pentacene nanocrystal is studied. Combination of time‐dependent density functional theory (TDDFT) with experiment allows for identification of the observed emission line as a mixed Frenkel and charge‐transfer exciton with main polarization perpendicular to the electric field of the STM.