The role of OLED emissive layer polarization in sub-turn-on charge accumulation

Evgeny Pakhomenko; Russell J. Holmes

doi:10.1117/12.2633591

The role of OLED emissive layer polarization in sub-turn-on charge accumulation

Evgeny Pakhomenko, Russell J. Holmes

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

1 Scopus citations

Abstract

Preferential alignment of molecular permanent dipole moments, known as spontaneous orientation polarization (SOP), is present in many materials employed in the active layers of organic light-emitting devices (OLEDs). This phenomenon leads to the formation of bound polarization charge, which is compensated by polaron accumulation at voltages below turn-on. While most prior work has focused on polarization in the device electron transport layer (ETL), here we examine the impact of emissive layer SOP by systematically probing polaron accumulation and exciton-polaron quenching in phosphorescent OLEDs. To gain a deeper understanding of polaron accumulation, device capacitance is systematically probed as a function of voltage across samples with polar and nonpolar emissive layers. We find that capacitance measurements can be used to track not only the number of accumulated charges, but also its location within the device active layers. This study provides an analysis framework that allows further insights on the charge accumulation process in OLEDs, thus improving our understanding of SOP in OLEDs.

Original language	English (US)
Title of host publication	Organic and Hybrid Light Emitting Materials and Devices XXVI
Editors	Chihaya Adachi, Tae-Woo Lee, Franky So
Publisher	SPIE
ISBN (Electronic)	9781510654006
DOIs	https://doi.org/10.1117/12.2633591
State	Published - 2022
Externally published	Yes
Event	Organic and Hybrid Light Emitting Materials and Devices XXVI 2022 - San Diego, United States Duration: Aug 21 2022 → Aug 23 2022

Publication series

Name	Proceedings of SPIE - The International Society for Optical Engineering
Volume	12208
ISSN (Print)	0277-786X
ISSN (Electronic)	1996-756X

Conference

Conference	Organic and Hybrid Light Emitting Materials and Devices XXVI 2022
Country/Territory	United States
City	San Diego
Period	8/21/22 → 8/23/22

Bibliographical note

Funding Information:
Funding and support for this work was provided by the Ronald L. and Janet A. Christenson Chair in Renewable Energy and Ronald & Beverly Sundahl Fellowship. The authors acknowledge the lab of Prof. C. D. Frisbie for the use of the potentiostat.

Publisher Copyright:
© 2022 SPIE.

Keywords

bimolecular quenching
capacitance
displacement current measurements
external quantum efficiency
molecular anisotropy
OLED
phosphorescence
photoluminescence

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The role of OLED emissive layer polarization in sub-turn-on charge accumulation. / Pakhomenko, Evgeny; Holmes, Russell J.
Organic and Hybrid Light Emitting Materials and Devices XXVI. ed. / Chihaya Adachi; Tae-Woo Lee; Franky So. SPIE, 2022. 122080A (Proceedings of SPIE - The International Society for Optical Engineering; Vol. 12208).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

Pakhomenko, E & Holmes, RJ 2022, The role of OLED emissive layer polarization in sub-turn-on charge accumulation. in C Adachi, T-W Lee & F So (eds), Organic and Hybrid Light Emitting Materials and Devices XXVI., 122080A, Proceedings of SPIE - The International Society for Optical Engineering, vol. 12208, SPIE, Organic and Hybrid Light Emitting Materials and Devices XXVI 2022, San Diego, United States, 8/21/22. https://doi.org/10.1117/12.2633591

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abstract = "Preferential alignment of molecular permanent dipole moments, known as spontaneous orientation polarization (SOP), is present in many materials employed in the active layers of organic light-emitting devices (OLEDs). This phenomenon leads to the formation of bound polarization charge, which is compensated by polaron accumulation at voltages below turn-on. While most prior work has focused on polarization in the device electron transport layer (ETL), here we examine the impact of emissive layer SOP by systematically probing polaron accumulation and exciton-polaron quenching in phosphorescent OLEDs. To gain a deeper understanding of polaron accumulation, device capacitance is systematically probed as a function of voltage across samples with polar and nonpolar emissive layers. We find that capacitance measurements can be used to track not only the number of accumulated charges, but also its location within the device active layers. This study provides an analysis framework that allows further insights on the charge accumulation process in OLEDs, thus improving our understanding of SOP in OLEDs.",

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N2 - Preferential alignment of molecular permanent dipole moments, known as spontaneous orientation polarization (SOP), is present in many materials employed in the active layers of organic light-emitting devices (OLEDs). This phenomenon leads to the formation of bound polarization charge, which is compensated by polaron accumulation at voltages below turn-on. While most prior work has focused on polarization in the device electron transport layer (ETL), here we examine the impact of emissive layer SOP by systematically probing polaron accumulation and exciton-polaron quenching in phosphorescent OLEDs. To gain a deeper understanding of polaron accumulation, device capacitance is systematically probed as a function of voltage across samples with polar and nonpolar emissive layers. We find that capacitance measurements can be used to track not only the number of accumulated charges, but also its location within the device active layers. This study provides an analysis framework that allows further insights on the charge accumulation process in OLEDs, thus improving our understanding of SOP in OLEDs.

AB - Preferential alignment of molecular permanent dipole moments, known as spontaneous orientation polarization (SOP), is present in many materials employed in the active layers of organic light-emitting devices (OLEDs). This phenomenon leads to the formation of bound polarization charge, which is compensated by polaron accumulation at voltages below turn-on. While most prior work has focused on polarization in the device electron transport layer (ETL), here we examine the impact of emissive layer SOP by systematically probing polaron accumulation and exciton-polaron quenching in phosphorescent OLEDs. To gain a deeper understanding of polaron accumulation, device capacitance is systematically probed as a function of voltage across samples with polar and nonpolar emissive layers. We find that capacitance measurements can be used to track not only the number of accumulated charges, but also its location within the device active layers. This study provides an analysis framework that allows further insights on the charge accumulation process in OLEDs, thus improving our understanding of SOP in OLEDs.

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The role of OLED emissive layer polarization in sub-turn-on charge accumulation

Abstract

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Bibliographical note

Keywords

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