Issue 20, 2020

Inkjet printing a small-molecule binary emitting layer for organic light-emitting diodes

Abstract

For inkjet-printed organic light-emitting diodes, it is critical to obtain a homogeneous small molecule-based emitting film. In contrast to the conventional strategy of utilizing mixed solvents, we have successfully inkjet printed a binary electrophosphorescent emitter with a single solvent. The binary emitter consists of a new host material 3-(3,6-di-t-butylcarbazol-9-yl)-3′-(2-(4-t-butylphenyl)benzoimidazol-1-yl)-[1,1′-biphenyl], and an iridium complex dopant bis(2-methyldibenzo[f,h]quinoxaline)(acetylacetonate)-iridium(III) (Ir(MDQ)2(acac)). Compatible with Ir(MDQ)2(acac), the newly developed host is highly soluble and amorphous with a glass transition temperature of 137 °C upon cooling from the melt. The inkjet printability and film morphology of the emitting layer are strongly dependent both on the substrates and the solvents. With o-dichlorobenzene (o-DCB) as the single solvent, and poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(p-butylphenyl))diphenylamine)] (TFB) as the hole transporting layer, a uniform emitter film morphology without any coffee ring is obtained. The phosphorescent OLED with the inkjet-printed emitter yields a maximum current efficiency of 17.89 cd A−1, comparable to that of Ir(MDQ)2(acac)-based OLEDs with a spin-cast emitter.

Graphical abstract: Inkjet printing a small-molecule binary emitting layer for organic light-emitting diodes

Supplementary files

Article information

Article type
Paper
Submitted
06 Feb 2020
Accepted
03 Apr 2020
First published
04 Apr 2020

J. Mater. Chem. C, 2020,8, 6906-6913

Inkjet printing a small-molecule binary emitting layer for organic light-emitting diodes

L. Mu, M. He, C. Jiang, J. Wang, C. Mai, X. Huang, H. Zheng, J. Wang, X. Zhu and J. Peng, J. Mater. Chem. C, 2020, 8, 6906 DOI: 10.1039/D0TC00628A

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