Role of delta-hole-doped interfaces at Ohmic contacts to organic semiconductors
Journal
Physical review letters
Journal Volume
103
Journal Issue
3
Date Issued
2009-07-17
Author(s)
Zhou, Mi
Chua, Lay-Lay
Png, Rui-Qi
Sivaramakrishnan, Sankaran
Chia, Perq-Jon
Wee, Andrew T S
Friend, Richard H
Ho, Peter K H
Abstract
An electromodulated absorption spectroscopy study of the contact between an organic semiconductor (OSC) poly(2,5-dialkoxy-p-phenylenevinylene) and p-doped poly(3,4-ethylenedioxythiophene) electrodes of different work functions (phivac) reveals direct evidence for the formation of a hole-doped layer at the OSC interface in equilibrium with high-phivac electrodes. When the hole density at this interface exceeds a few 10(11) cm(-2), degenerate "bandlike" polaron states emerge. This appears to be crucial to furnish efficient carrier injection into the bulk of the OSC to achieve Ohmic injection. The gap measured by ultraviolet photoemission between the electrode Fermi level and the OSC transport level (typically pinned at 0.6 eV) does not reflect the true injection barrier.
Subjects
LIGHT-EMITTING-DIODES; CONJUGATED POLYMER; INJECTION; MODEL; ENERGIES; POLARONS; DEVICES; METAL
Publisher
AMER PHYSICAL SOC
Type
journal article