Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics
Abstract
As carriers slowly move through a disordered energy landscape in organic semiconductors, tiny spatial variations in spin dynamics relieve spin blocking at transport bottlenecks or in the electron-hole recombination process that produces light. Large room-temperature magnetic-field effects (MFEs) ensue in the conductivity and luminescence. Sources of variable spin dynamics generate much larger MFEs if their spatial structure is correlated on the nanoscale with the energetic sites governing conductivity or luminescence such as in coevaporated organic blends within which the electron resides on one molecule and the hole on the other (an exciplex). Here, we show that exciplex recombination in blends exhibiting thermally activated delayed fluorescence produces MFEs in excess of 60% at room temperature. In addition, effects greater than 4000% can be achieved by tuning the device’s current-voltage response curve by device conditioning. Both of these immense MFEs are the largest reported values for their device type at room temperature. Our theory traces this MFE and its unusual temperature dependence to changes in spin mixing between triplet exciplexes and light-emitting singlet exciplexes. In contrast, spin mixing of excitons is energetically suppressed, and thus spin mixing produces comparatively weaker MFEs in materials emitting light from excitons by affecting the precursor pairs.more »
- Authors:
- Publication Date:
- Research Org.:
- Univ. of Iowa, Iowa City, IA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- OSTI Identifier:
- 1237121
- Alternate Identifier(s):
- OSTI ID: 1242362
- Grant/Contract Number:
- SC0014336
- Resource Type:
- Published Article
- Journal Name:
- Physical Review. X
- Additional Journal Information:
- Journal Name: Physical Review. X Journal Volume: 6 Journal Issue: 1; Journal ID: ISSN 2160-3308
- Publisher:
- American Physical Society
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
Citation Formats
Wang, Yifei, Sahin-Tiras, Kevser, Harmon, Nicholas J., Wohlgenannt, Markus, and Flatté, Michael E. Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics. United States: N. p., 2016.
Web. doi:10.1103/PhysRevX.6.011011.
Wang, Yifei, Sahin-Tiras, Kevser, Harmon, Nicholas J., Wohlgenannt, Markus, & Flatté, Michael E. Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics. United States. https://doi.org/10.1103/PhysRevX.6.011011
Wang, Yifei, Sahin-Tiras, Kevser, Harmon, Nicholas J., Wohlgenannt, Markus, and Flatté, Michael E. Fri .
"Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics". United States. https://doi.org/10.1103/PhysRevX.6.011011.
@article{osti_1237121,
title = {Immense Magnetic Response of Exciplex Light Emission due to Correlated Spin-Charge Dynamics},
author = {Wang, Yifei and Sahin-Tiras, Kevser and Harmon, Nicholas J. and Wohlgenannt, Markus and Flatté, Michael E.},
abstractNote = {As carriers slowly move through a disordered energy landscape in organic semiconductors, tiny spatial variations in spin dynamics relieve spin blocking at transport bottlenecks or in the electron-hole recombination process that produces light. Large room-temperature magnetic-field effects (MFEs) ensue in the conductivity and luminescence. Sources of variable spin dynamics generate much larger MFEs if their spatial structure is correlated on the nanoscale with the energetic sites governing conductivity or luminescence such as in coevaporated organic blends within which the electron resides on one molecule and the hole on the other (an exciplex). Here, we show that exciplex recombination in blends exhibiting thermally activated delayed fluorescence produces MFEs in excess of 60% at room temperature. In addition, effects greater than 4000% can be achieved by tuning the device’s current-voltage response curve by device conditioning. Both of these immense MFEs are the largest reported values for their device type at room temperature. Our theory traces this MFE and its unusual temperature dependence to changes in spin mixing between triplet exciplexes and light-emitting singlet exciplexes. In contrast, spin mixing of excitons is energetically suppressed, and thus spin mixing produces comparatively weaker MFEs in materials emitting light from excitons by affecting the precursor pairs. Demonstration of immense MFEs in common organic blends provides a flexible and inexpensive pathway towards magnetic functionality and field sensitivity in current organic devices without patterning the constituent materials on the nanoscale. In conclusion, magnetic fields increase the power efficiency of unconditioned devices by 30% at room temperature, also showing that magnetic fields may increase the efficiency of the thermally activated delayed fluorescence process.},
doi = {10.1103/PhysRevX.6.011011},
journal = {Physical Review. X},
number = 1,
volume = 6,
place = {United States},
year = {Fri Feb 05 00:00:00 EST 2016},
month = {Fri Feb 05 00:00:00 EST 2016}
}
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https://doi.org/10.1103/PhysRevX.6.011011
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