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Title: Density and mobility effects of the majority carriers in organic semiconductors under light excitation

This study demonstrates that the effect of light excitation on the density and the mobility of the majority carriers can be explored in organic semiconductors by modulated photocurrent spectroscopy. The spectra of phase and amplitude of the modulated photocurrent of pentacene films indicate a significant increase in the density of the photogenerated mobile holes (majority carriers). This increase is accompanied by a comparatively much smaller increase of the steady state photocurrent response which can be reconciled with a decrease in the mobility (μ) of holes. The decrease of μ is supported from an unusual increase of the Y/μ ratio of the out-of-phase modulated photocurrent (Y) signal to the mobility under light excitation. It is proposed that the mobile holes, which are generated from the dissociation of the light-created excitons more likely near the pentacene-substrate interface by electron trapping, populate grain boundaries charging them and producing a downward band bending. As a result, potential energy barriers are build up which limit the transport of holes interacting through trapping-detrapping with deep partially occupied traps in the charged grain boundaries. On the other hand, the transport of holes interacting through trapping-detrapping with empty traps is found unaffected.
Authors:
; ;  [1]
  1. Department of Electrical and Computer Engineering, University of Patras, 26504 Patra (Greece)
Publication Date:
OSTI Identifier:
22412951
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 3; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CARRIER MOBILITY; CHARGE CARRIERS; DISSOCIATION; ELECTRONS; EMISSION SPECTROSCOPY; EXCITATION; EXCITONS; FILMS; GRAIN BOUNDARIES; HOLES; INTERFACES; ORGANIC SEMICONDUCTORS; PENTACENE; PHOTOCURRENTS; POTENTIAL ENERGY; SUBSTRATES; TRAPPING; TRAPS; VISIBLE RADIATION