Presentation Title

Effect of the Dipole Position on the Emission Characteristics in Microcavity Organic Light Emitting Diodes

Project Collaborators

David Allemeier (Co-author)

Abstract

Organic light emitting diodes (OLED) employing two planar metallic electrodes encasing the organic layers form a microcavity etalon. This structure allows a control on the output emission characteristic of the light source resulting in a significant narrowing of the emission bandwidth and angular dispersion of light. We investigate the emission spectra using a single organic emitter molecule, just by engineering the position of the dipole emitter in the microcavity structure alone. We use Tris(8-hydroxyquinolinato)aluminium, Alq3, as the emissive layer (EML) with the electron transport layers (ETL) and hole transport layers (HTL) added in between the metal electrodes. The position of the EML was varied by varying the relative thickness of the ETL and HTL and maintaining a fixed total thickness of the device structure. The output characteristic of the microcavity is affected by its optical path length. Here we test this hypothesis that a fixed optical pathlength generates the same optical characteristics even with the changing dipole position. Varying the thickness of the ETL, EML, and HTL layers without changing the total optical pathlength of the device in principle generates the same output characteristic of light. We find that fixing the optical pathlength in the cavity functionally fixes the peak emission wavelength, but the dipole position within the cavity has strong impact on the efficiency of outcoupling of light and on the polarization.

Primary Faculty Mentor Name

Matthew S. White

Status

Graduate

Student College

Graduate College

Program/Major

Materials Science

Primary Research Category

Engineering & Physical Sciences

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Effect of the Dipole Position on the Emission Characteristics in Microcavity Organic Light Emitting Diodes

Organic light emitting diodes (OLED) employing two planar metallic electrodes encasing the organic layers form a microcavity etalon. This structure allows a control on the output emission characteristic of the light source resulting in a significant narrowing of the emission bandwidth and angular dispersion of light. We investigate the emission spectra using a single organic emitter molecule, just by engineering the position of the dipole emitter in the microcavity structure alone. We use Tris(8-hydroxyquinolinato)aluminium, Alq3, as the emissive layer (EML) with the electron transport layers (ETL) and hole transport layers (HTL) added in between the metal electrodes. The position of the EML was varied by varying the relative thickness of the ETL and HTL and maintaining a fixed total thickness of the device structure. The output characteristic of the microcavity is affected by its optical path length. Here we test this hypothesis that a fixed optical pathlength generates the same optical characteristics even with the changing dipole position. Varying the thickness of the ETL, EML, and HTL layers without changing the total optical pathlength of the device in principle generates the same output characteristic of light. We find that fixing the optical pathlength in the cavity functionally fixes the peak emission wavelength, but the dipole position within the cavity has strong impact on the efficiency of outcoupling of light and on the polarization.