Stark Effect of Hybrid Charge Transfer States at Planar ZnO/Organic Interfaces

• Main Authors: Hörmann, Ulrich, Zeiske, Stefan, Piersimoni, Fortunato, Hoffmann, Lukas, Schlesinger, Raphael, Koch, Norbert, Riedl, Thomas, Andrienko, Denis, Neher, Dieter
• Format: Journal Article
• Language: English
• Published: 01-08-2018
• Subjects: Physics - Mesoscale and Nanoscale Physics; Physics - Soft Condensed Matter
• DOI: 10.48550/arxiv.1808.00295

Phys. Rev. B 98, 155312 (2018) We investigate the bias-dependence of the hybrid charge transfer state
emission at planar heterojunctions between the metal oxide acceptor ZnO and
three donor molecules. The electroluminescence peak energy linearly increases
with the applied bias, saturating at high fields. Variation of the organic
layer thickness and deliberate change of the ZnO conductivity through
controlled photo-doping allow us to confirm that this bias-induced spectral
shifts relate to the internal electric field in the organic layer rather than
the filling of states at the hybrid interface. We show that existing continuum
models overestimate the hole delocalization and propose a simple electrostatic
model in which the linear and quadratic Stark effects are explained by the
electrostatic interaction of a strongly polarizable molecular cation with its
mirror image.