Absolute hole injection efficiency from pre-treated indium tin oxide electrodes into poly(9,9-dioctylflourene) and its copolymers

Alasdair J. Campbell; Donal D. C. Bradley; Homer Antoniadis

doi:10.1117/12.416896

2 February 2001 Absolute hole injection efficiency from pre-treated indium tin oxide electrodes into poly(9,9-dioctylflourene) and its copolymers

Alasdair J. Campbell, Donal D. C. Bradley, Homer Antoniadis

Author Affiliations +

Proceedings Volume 4105, Organic Light-Emitting Materials and Devices IV; (2001) https://doi.org/10.1117/12.416896
Event: International Symposium on Optical Science and Technology, 2000, San Diego, CA, United States

Abstract

If conduction in a polymer light emitting diode is by trap- free, space-charge-limited current (TFSCLC), the injecting contact must be ohmic. Such an ohmic contact is, by definition, the perfect injecting electrode. The absolute injection efficiency of any specific contact can therefore be quantified by the ratio of the actual current density, J, to that of the ideal TFSCLC current density, J_TFSCLC. In this work we report on the injection efficiency of positive carriers from pretreated indium tin oxide (ITO) and metal electrodes into poly(9,9-dioctylfluorene) (PFO) and two representative copolymers. The ITO was either washed only in solvents, exposed to an oxygen plasma or coated in a film of poly(ethylenedioxythiophene)/polystyrenesulphonic acid blend. Time-of-flight photocurrent measurements were used to find the positive carrier mobility, (mu) _p, so that J_TFSCLC could be calculated. Dark injection current transient measurements were used to confirm the presence or absence of TFSCLC conduction. Steady-state, current density- voltage measurements were then used to compare the actual current to J_TFSCLC, thus allowing the absolute injection efficiency, J/J(subscript TFSCLC, to be calculated.

Citation Download Citation

Alasdair J. Campbell, Donal D. C. Bradley, and Homer Antoniadis "Absolute hole injection efficiency from pre-treated indium tin oxide electrodes into poly(9,9-dioctylflourene) and its copolymers", Proc. SPIE 4105, Organic Light-Emitting Materials and Devices IV, (2 February 2001); https://doi.org/10.1117/12.416896

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