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Title: Electrical conduction of LiF interlayers in organic diodes

An interlayer of LiF in between a metal and an organic semiconductor is commonly used to improve the electron injection. Here, we investigate the effect of moderate bias voltages on the electrical properties of Al/LiF/poly(spirofluorene)/Ba/Al diodes by systematically varying the thickness of the LiF layer (2-50 nm). Application of forward bias V below the bandgap of LiF (V < E{sub g} ∼ 14 V) results in reversible formation of an electrical double layer at the LiF/poly(spirofluorene) hetero-junction. Electrons are trapped on the poly(spirofluorene) side of the junction, while positively charged defects accumulate in the LiF with number densities as high as 10{sup 25}/m{sup 3}. Optoelectronic measurements confirm the built-up of aggregated, ionized F centres in the LiF as the positive trapped charges. The charged defects result in efficient transport of electrons from the polymer across the LiF, with current densities that are practically independent of the thickness of the LiF layer.
Authors:
; ;  [1] ;  [2] ;  [3]
  1. Molecular Materials and Nanosystems and Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)
  2. Instituto de Telecomunicações, Av. Rovisco, Pais, 1, 1049–001, Lisboa, Portugal and Universidade do Algarve, Campus de Gambelas, 8005-139 Faro (Portugal)
  3. Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany and King Abdulaziz University, Jeddah (Saudi Arabia)
Publication Date:
OSTI Identifier:
22402894
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 15; Other Information: (c) 2015 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALUMINIUM; CURRENT DENSITY; ELECTRIC CONDUCTIVITY; ELECTRIC POTENTIAL; ELECTRON BEAM INJECTION; ELECTRONIC STRUCTURE; ELECTRONS; ENERGY GAP; F CENTERS; HETEROJUNCTIONS; LAYERS; LITHIUM FLUORIDES; ORGANIC SEMICONDUCTORS; POLYMERS; TRAPPING