n-Doping of a Low-Electron-Affinity Polymer Used as an Electron-Transport Layer in Organic Light-Emitting Diodes

Smith HL, Dull JT, Longhi E, Barlow S, Rand BP, Marder SR, Kahn A (2020)

Publication Language: English

Publication Type: Journal article

Publication year: 2020

Journal

Advanced Functional Materials Wiley-VCH Verlag

Book Volume: 30

Article Number: 2000328

URI: https://doi.org/10.1038/s41586-019-1339-4

DOI: 10.1002/adfm.202000328

Abstract

n-Doping electron-transport layers (ETLs) increases their conductivity and improves electron injection into organic light-emitting diodes (OLEDs). Because of the low electron affinity and large bandgaps of ETLs used in green and blue OLEDs, n-doping has been notoriously more difficult for these materials. In this work, n-doping of the polymer poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)] (F8BT) is demonstrated via solution processing, using the air-stable n-dopant (pentamethylcyclopentadienyl) (1,3,5-trimethylbenzene)ruthenium dimer [RuCp*Mes]2. Undoped and doped F8BT films are characterized using ultraviolet and inverse photoelectron spectroscopy. The ionization energy and electron affinity of the undoped F8BT are found to be 5.8 and 2.8 eV, respectively. Upon doping F8BT with [RuCp*Mes]2, the Fermi level shifts to within 0.25 eV of the F8BT lowest unoccupied molecular orbital, which is indicative of n-doping. Conductivity measurements reveal a four orders of magnitude increase in the conductivity upon doping and irradiation with ultraviolet light. The [RuCp*Mes]2-doped F8BT films are incorporated as an ETL into phosphorescent green OLEDs, and the luminance is improved by three orders of magnitude when compared to identical devices with an undoped F8BT ETL.

Authors with CRIS profile

Hannah Smith

Involved external institutions

Georgia Institute of Technology US United States (USA) (US) Princeton University US United States (USA) (US)

How to cite

APA:

Smith, H.L., Dull, J.T., Longhi, E., Barlow, S., Rand, B.P., Marder, S.R., & Kahn, A. (2020). n-Doping of a Low-Electron-Affinity Polymer Used as an Electron-Transport Layer in Organic Light-Emitting Diodes. Advanced Functional Materials, 30. https://dx.doi.org/10.1002/adfm.202000328

MLA:

Smith, Hannah L, et al. "n-Doping of a Low-Electron-Affinity Polymer Used as an Electron-Transport Layer in Organic Light-Emitting Diodes." Advanced Functional Materials 30 (2020).

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