Carrier tunneling and device characteristics in polymer light-emitting diodes

Book · Sat Dec 31 04:00:00 EST 1994

OSTI ID:100956

Parker, I D ^[1]

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1. UNIAX Corp., Santa Barbara, CA (United States)

This paper demonstrates that the characteristics of light-emitting diodes (LEDs) based upon MEH-PPV, (more fully known as poly(2-methoxy,5-(2{prime}-ethyl-hexoxy)-1,4-phenylene-vinylene)), are determined by tunneling of both the holes and the electrons through interface barriers caused by the band offset between the polymer and the electrodes. It is shown that manipulating these offsets can control the useful operating-voltage of the device as well as its efficiency. A model is developed which clearly explains the device characteristics of a wide range of diodes based upon MEH-PPV. The turn-on voltage for an ideal device is shown to be equal to the band-gap, i.e. 2.1 eV for MEH-PPV, and is slightly lower at 1.8 eV for an indium-tin oxide/MEH-PPV/Ca device. If there is a significant difference in the barrier height, the smaller of the two barriers controls the I-V characteristics while the larger barrier determines the device efficiency. In ITO/MEH-PPV/Ca devices, the barrier to hole injection is 0.2 eV and the barrier to electron injection is only 0.1 eV. The authors show that reducing the hole barrier to 0.1 eV using a polyaniline anode halves the operating voltage and increases device efficiency.

• OSTI ID: 100956
• Report Number(s): CONF-940142--; ISBN 0-8194-1439-5
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
ELECTROLUMINESCENCE
ELECTRONIC STRUCTURE
EXPERIMENTAL DATA
FIELD EMISSION
LIGHT EMITTING DIODES
MATERIALS
MATHEMATICAL MODELS
PERFORMANCE
SEMICONDUCTOR MATERIALS
TUNNEL EFFECT