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Oono T, Okada T, Sasaki T, Inagaki K, Ushiku T, Shimizu T, Hatakeyama T, Fukagawa H. Unlocking the Full Potential of Electron- Acceptor Molecules for Efficient and Stable Hole Injection. Adv Mater 2023; 35:e2210413. [PMID: 36571784 DOI: 10.1002/adma.202210413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/19/2022] [Indexed: 06/17/2023]
Abstract
Understanding the hole-injection mechanism and improving the hole-injection property are of pivotal importance in the future development of organic optoelectronic devices. Electron-acceptor molecules with high electron affinity (EA) are widely used in electronic applications, such as hole injection and p-doping. Although p-doping has generally been studied in terms of matching the ionization energy (IE) of organic semiconductors with the EA of acceptor molecules, little is known about the effect of the EA of acceptor molecules on the hole-injection property. In this work, the hole-injection mechanism in devices is completely clarified, and a strategy to optimize the hole-injection property of the acceptor molecule is developed. Efficient and stable hole injection is found to be possible even into materials with IEs as high as 5.8 eV by controlling the charged state of an acceptor molecule with an EA of about 5.0 eV. This excellent hole-injection property enables direct hole injection into an emitting layer, realizing a pure blue organic light-emitting diode with an extraordinarily low turn-on voltage of 2.67 V, a power efficiency of 29 lm W-1 , an external quantum efficiency of 28% and a Commission Internationale de l'Eclairage y coordinate of less than 0.10.
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Affiliation(s)
- Taku Oono
- Japan Broadcasting Corporation (NHK), Science and Technology Research Laboratories, 1-10-11, Kinuta, Setagaya-ku, Tokyo, 157-8510, Japan
| | - Takuya Okada
- Japan Broadcasting Corporation (NHK), Science and Technology Research Laboratories, 1-10-11, Kinuta, Setagaya-ku, Tokyo, 157-8510, Japan
| | - Tsubasa Sasaki
- Japan Broadcasting Corporation (NHK), Science and Technology Research Laboratories, 1-10-11, Kinuta, Setagaya-ku, Tokyo, 157-8510, Japan
| | - Kaito Inagaki
- Department of Physics, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8610, Japan
| | - Takuma Ushiku
- Department of Physics, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8610, Japan
| | - Takahisa Shimizu
- Japan Broadcasting Corporation (NHK), Science and Technology Research Laboratories, 1-10-11, Kinuta, Setagaya-ku, Tokyo, 157-8510, Japan
| | - Takuji Hatakeyama
- Department of Chemistry, School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Hirohiko Fukagawa
- Japan Broadcasting Corporation (NHK), Science and Technology Research Laboratories, 1-10-11, Kinuta, Setagaya-ku, Tokyo, 157-8510, Japan
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Müller K, Schmidt N, Link S, Riedel R, Bock J, Malone W, Lasri K, Kara A, Starke U, Kivala M, Stöhr M. Triphenylene-Derived Electron Acceptors and Donors on Ag(111): Formation of Intermolecular Charge-Transfer Complexes with Common Unoccupied Molecular States. Small 2019; 15:e1901741. [PMID: 31264784 DOI: 10.1002/smll.201901741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 06/14/2019] [Indexed: 06/09/2023]
Abstract
Over the past years, ultrathin films consisting of electron donating and accepting molecules have attracted increasing attention due to their potential usage in optoelectronic devices. Key parameters for understanding and tuning their performance are intermolecular and molecule-substrate interactions. Here, the formation of a monolayer thick blend of triphenylene-based organic donor and acceptor molecules from 2,3,6,7,10,11-hexamethoxytriphenylene (HAT) and 1,4,5,8,9,12-hexaazatriphenylenehexacarbonitrile (HATCN), respectively, on a silver (111) surface is reported. Scanning tunneling microscopy and spectroscopy, valence and core level photoelectron spectroscopy, as well as low-energy electron diffraction measurements are used, complemented by density functional theory calculations, to investigate both the electronic and structural properties of the homomolecular as well as the intermixed layers. The donor molecules are weakly interacting with the Ag(111) surface, while the acceptor molecules show a strong interaction with the substrate leading to charge transfer and substantial buckling of the top silver layer and of the adsorbates. Upon mixing acceptor and donor molecules, strong hybridization occurs between the two different molecules leading to the emergence of a common unoccupied molecular orbital located at both the donor and acceptor molecules. The donor acceptor blend studied here is, therefore, a compelling candidate for organic electronics based on self-assembled charge-transfer complexes.
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Affiliation(s)
- Kathrin Müller
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, Netherlands
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569, Stuttgart, Germany
| | - Nico Schmidt
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, Netherlands
| | - Stefan Link
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569, Stuttgart, Germany
| | - René Riedel
- Department of Chemistry and Pharmacy, University of Erlangen-Nürnberg, Nikolaus-Fiebiger-Strasse 10, D-91058, Erlangen, Germany
| | - Julian Bock
- Organisch-Chemisches Institut & Centre for Advanced Materials, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270 & 225, 69120, Heidelberg, Germany
| | - Walter Malone
- Department of Physics, University of Central Florida, Orlando, FL 32816, USA
| | - Karima Lasri
- Department of Physics, University of Central Florida, Orlando, FL 32816, USA
| | - Abdelkader Kara
- Department of Physics, University of Central Florida, Orlando, FL 32816, USA
| | - Ulrich Starke
- Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569, Stuttgart, Germany
| | - Milan Kivala
- Organisch-Chemisches Institut & Centre for Advanced Materials, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270 & 225, 69120, Heidelberg, Germany
| | - Meike Stöhr
- Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747, AG, Groningen, Netherlands
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