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All-organic sulfonium salts acting as efficient solution processed electron injection layer for PLEDs

All-organic sulfonium salts acting as efficient solution processed electron injection layer for PLEDs
All-organic sulfonium salts acting as efficient solution processed electron injection layer for PLEDs

Herein we introduce the all-organic triphenylsulfonium (TPS) salts cathode interfacial layers (CILs), deposited from their methanolic solution, as a new simple strategy for circumventing the use of unstable low work function metals and obtaining charge balance and high electroluminescence efficiency in polymer light-emitting diodes (PLEDs). In particular, we show that the incorporation of TPS-triflate or TPS-nonaflate at the polymer/Al interface improved substantially the luminous efficiency of the device (from 2.4 to 7.9 cd/A) and reduced the turn-on and operating voltage, whereas an up to 4-fold increase in brightness (∼11 250 cd/m2 for TPS-triflate and ∼14 682 cd/m2 for TPS-nonaflate compared to ∼3221 cd/m2 for the reference device) was observed in poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-2, 1′,3-thiadiazole)] (F8BT)-based PLEDs. This was mainly attributed to the favorable decrease of the electron injection barrier, as derived from the open-circuit voltage (Voc) measurements, which was also assisted by the conduction of electrons through the triphenylsulfonium salt sites. Density functional theory calculations indicated that the total energy of the anionic (reduced) form of the salt, that is, upon placing an electron to its lowest unoccupied molecular orbital, is lower than its neutral state, rendering the TPS-salts stable upon electron transfer in the solid state. Finally, the morphology optimization of the TPS-salt interlayer through controlling the processing parameters was found to be critical for achieving efficient electron injection and transport at the respective interfaces.

cathode interfacial layer, counterions, electron transport, nonaflate, OLEDs, triflate
1944-8244
12346-12354
Georgiadou, Dimitra G.
84977176-3678-4fb3-a3dd-2044a49c853b
Vasilopoulou, Maria
aad1381e-d091-4090-8c7c-b74bed22393d
Palilis, Leonidas C.
b09e9554-54da-4be5-aa08-bda894e2b86f
Petsalakis, Ioannis D.
fa1d2c2e-5c95-40dc-ad85-85f0374402d4
Theodorakopoulos, Giannoula
cd4de8da-b206-4b04-8a25-d35108628cba
Constantoudis, Vassilios
4d35166b-4d75-4caa-ae27-c991b51a01c3
Kennou, Stella
7ca6a6bd-6a05-4110-b3da-c8807f798370
Karantonis, Antonis
38bfa4e4-0424-49dc-b4ff-d81193afcb31
Dimotikali, Dimitra
9c6d5002-c742-4576-b6dc-048acb0f1420
Argitis, Panagiotis
ab9c4ea6-3dd2-4e34-935d-81bfb360f358
Georgiadou, Dimitra G.
84977176-3678-4fb3-a3dd-2044a49c853b
Vasilopoulou, Maria
aad1381e-d091-4090-8c7c-b74bed22393d
Palilis, Leonidas C.
b09e9554-54da-4be5-aa08-bda894e2b86f
Petsalakis, Ioannis D.
fa1d2c2e-5c95-40dc-ad85-85f0374402d4
Theodorakopoulos, Giannoula
cd4de8da-b206-4b04-8a25-d35108628cba
Constantoudis, Vassilios
4d35166b-4d75-4caa-ae27-c991b51a01c3
Kennou, Stella
7ca6a6bd-6a05-4110-b3da-c8807f798370
Karantonis, Antonis
38bfa4e4-0424-49dc-b4ff-d81193afcb31
Dimotikali, Dimitra
9c6d5002-c742-4576-b6dc-048acb0f1420
Argitis, Panagiotis
ab9c4ea6-3dd2-4e34-935d-81bfb360f358

Georgiadou, Dimitra G., Vasilopoulou, Maria, Palilis, Leonidas C., Petsalakis, Ioannis D., Theodorakopoulos, Giannoula, Constantoudis, Vassilios, Kennou, Stella, Karantonis, Antonis, Dimotikali, Dimitra and Argitis, Panagiotis (2013) All-organic sulfonium salts acting as efficient solution processed electron injection layer for PLEDs. ACS Applied Materials and Interfaces, 5 (23), 12346-12354. (doi:10.1021/am402991b).

Record type: Article

Abstract

Herein we introduce the all-organic triphenylsulfonium (TPS) salts cathode interfacial layers (CILs), deposited from their methanolic solution, as a new simple strategy for circumventing the use of unstable low work function metals and obtaining charge balance and high electroluminescence efficiency in polymer light-emitting diodes (PLEDs). In particular, we show that the incorporation of TPS-triflate or TPS-nonaflate at the polymer/Al interface improved substantially the luminous efficiency of the device (from 2.4 to 7.9 cd/A) and reduced the turn-on and operating voltage, whereas an up to 4-fold increase in brightness (∼11 250 cd/m2 for TPS-triflate and ∼14 682 cd/m2 for TPS-nonaflate compared to ∼3221 cd/m2 for the reference device) was observed in poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-2, 1′,3-thiadiazole)] (F8BT)-based PLEDs. This was mainly attributed to the favorable decrease of the electron injection barrier, as derived from the open-circuit voltage (Voc) measurements, which was also assisted by the conduction of electrons through the triphenylsulfonium salt sites. Density functional theory calculations indicated that the total energy of the anionic (reduced) form of the salt, that is, upon placing an electron to its lowest unoccupied molecular orbital, is lower than its neutral state, rendering the TPS-salts stable upon electron transfer in the solid state. Finally, the morphology optimization of the TPS-salt interlayer through controlling the processing parameters was found to be critical for achieving efficient electron injection and transport at the respective interfaces.

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More information

e-pub ahead of print date: 7 November 2013
Published date: 11 December 2013
Keywords: cathode interfacial layer, counterions, electron transport, nonaflate, OLEDs, triflate

Identifiers

Local EPrints ID: 439829
URI: http://eprints.soton.ac.uk/id/eprint/439829
ISSN: 1944-8244
PURE UUID: 8a5fd2bd-e3ac-4bc0-8efe-5651b8ab94d2
ORCID for Dimitra G. Georgiadou: ORCID iD orcid.org/0000-0002-2620-3346

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Date deposited: 05 May 2020 16:30
Last modified: 07 Oct 2020 02:27

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Contributors

Author: Maria Vasilopoulou
Author: Leonidas C. Palilis
Author: Ioannis D. Petsalakis
Author: Giannoula Theodorakopoulos
Author: Vassilios Constantoudis
Author: Stella Kennou
Author: Antonis Karantonis
Author: Dimitra Dimotikali
Author: Panagiotis Argitis

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