Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films: a new design space for organic light-emitting diodes

Changmin Keum; Shiyi Liu; Akram Al-Shadeedi; Vikash Kaphle; Michiel Koen Callens; Lu Han; Kristiaan Neyts; Hongping Zhao; Malte Christian Gather; Scott D. Bunge; Robert J. Twieg; Antal Jakli; Björn Lüssem

doi:10.1038/s41598-018-19157-9

Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films: a new design space for organic light-emitting diodes

Changmin Keum, Shiyi Liu, Akram Al-Shadeedi, Vikash Kaphle, Michiel Koen Callens, Lu Han, Kristiaan Neyts, Hongping Zhao, Malte Christian Gather, Scott D. Bunge, Robert J. Twieg, Antal Jakli, Björn Lüssem

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Abstract

Liquid-crystalline organic semiconductors exhibit unique properties that make them highly interesting for organic optoelectronic applications. Their optical and electrical anisotropies and the possibility to control the alignment of the liquid-crystalline semiconductor allow not only to optimize charge carrier transport, but to tune the optical property of organic thin-film devices as well. In this study, the molecular orientation in a liquid-crystalline semiconductor film is tuned by a novel blading process as well as by different annealing protocols. The altered alignment is verified by cross-polarized optical microscopy and spectroscopic ellipsometry. It is shown that a change in alignment of the liquid-crystalline semiconductor improves charge transport in single charge carrier devices profoundly. Comparing the current-voltage characteristics of single charge carrier devices with simulations shows an excellent agreement and from this an in-depth understanding of single charge carrier transport in two-terminal devices is obtained. Finally, p-i-n type organic light-emitting diodes (OLEDs) compatible with vacuum processing techniques used in state-of-the-art OLEDs are demonstrated employing liquid-crystalline host matrix in the emission layer.

Original language	English
Article number	699
Number of pages	12
Journal	Scientific Reports
Volume	8
DOIs	https://doi.org/10.1038/s41598-018-19157-9
Publication status	Published - 15 Jan 2018

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Keum, C., Liu, S., Al-Shadeedi, A., Kaphle, V., Koen Callens, M., Han, L., Neyts, K., Zhao, H., Gather, M. C., Bunge, S. D., Twieg, R. J., Jakli, A., & Lüssem, B. (2018). Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films: a new design space for organic light-emitting diodes. Scientific Reports, 8, Article 699. https://doi.org/10.1038/s41598-018-19157-9

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title = "Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films: a new design space for organic light-emitting diodes",

abstract = "Liquid-crystalline organic semiconductors exhibit unique properties that make them highly interesting for organic optoelectronic applications. Their optical and electrical anisotropies and the possibility to control the alignment of the liquid-crystalline semiconductor allow not only to optimize charge carrier transport, but to tune the optical property of organic thin-film devices as well. In this study, the molecular orientation in a liquid-crystalline semiconductor film is tuned by a novel blading process as well as by different annealing protocols. The altered alignment is verified by cross-polarized optical microscopy and spectroscopic ellipsometry. It is shown that a change in alignment of the liquid-crystalline semiconductor improves charge transport in single charge carrier devices profoundly. Comparing the current-voltage characteristics of single charge carrier devices with simulations shows an excellent agreement and from this an in-depth understanding of single charge carrier transport in two-terminal devices is obtained. Finally, p-i-n type organic light-emitting diodes (OLEDs) compatible with vacuum processing techniques used in state-of-the-art OLEDs are demonstrated employing liquid-crystalline host matrix in the emission layer.",

author = "Changmin Keum and Shiyi Liu and Akram Al-Shadeedi and Vikash Kaphle and {Koen Callens}, Michiel and Lu Han and Kristiaan Neyts and Hongping Zhao and Gather, {Malte Christian} and Bunge, {Scott D.} and Twieg, {Robert J.} and Antal Jakli and Bj{\"o}rn L{\"u}ssem",

note = "B.L. acknowledges financial support from the Binational Science Foundation under grant No 2014396 and from the National Science Foundation under grant No 1639073. C.K. acknowledges funding from the Kent State University Internal Post-Doctoral Competition. M.C.K. acknowledges funding from the Belgian Agentschap voor innovatie door wetenschap en techniek under grant No IWT 131498.",

year = "2018",

month = jan,

day = "15",

doi = "10.1038/s41598-018-19157-9",

language = "English",

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journal = "Scientific Reports",

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Keum, C, Liu, S, Al-Shadeedi, A, Kaphle, V, Koen Callens, M, Han, L, Neyts, K, Zhao, H, Gather, MC, Bunge, SD, Twieg, RJ, Jakli, A & Lüssem, B 2018, 'Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films: a new design space for organic light-emitting diodes', Scientific Reports, vol. 8, 699. https://doi.org/10.1038/s41598-018-19157-9

TY - JOUR

T1 - Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films

T2 - a new design space for organic light-emitting diodes

AU - Keum, Changmin

AU - Liu, Shiyi

AU - Al-Shadeedi, Akram

AU - Kaphle, Vikash

AU - Koen Callens, Michiel

AU - Han, Lu

AU - Neyts, Kristiaan

AU - Zhao, Hongping

AU - Gather, Malte Christian

AU - Bunge, Scott D.

AU - Twieg, Robert J.

AU - Jakli, Antal

AU - Lüssem, Björn

N1 - B.L. acknowledges financial support from the Binational Science Foundation under grant No 2014396 and from the National Science Foundation under grant No 1639073. C.K. acknowledges funding from the Kent State University Internal Post-Doctoral Competition. M.C.K. acknowledges funding from the Belgian Agentschap voor innovatie door wetenschap en techniek under grant No IWT 131498.

PY - 2018/1/15

Y1 - 2018/1/15

N2 - Liquid-crystalline organic semiconductors exhibit unique properties that make them highly interesting for organic optoelectronic applications. Their optical and electrical anisotropies and the possibility to control the alignment of the liquid-crystalline semiconductor allow not only to optimize charge carrier transport, but to tune the optical property of organic thin-film devices as well. In this study, the molecular orientation in a liquid-crystalline semiconductor film is tuned by a novel blading process as well as by different annealing protocols. The altered alignment is verified by cross-polarized optical microscopy and spectroscopic ellipsometry. It is shown that a change in alignment of the liquid-crystalline semiconductor improves charge transport in single charge carrier devices profoundly. Comparing the current-voltage characteristics of single charge carrier devices with simulations shows an excellent agreement and from this an in-depth understanding of single charge carrier transport in two-terminal devices is obtained. Finally, p-i-n type organic light-emitting diodes (OLEDs) compatible with vacuum processing techniques used in state-of-the-art OLEDs are demonstrated employing liquid-crystalline host matrix in the emission layer.

AB - Liquid-crystalline organic semiconductors exhibit unique properties that make them highly interesting for organic optoelectronic applications. Their optical and electrical anisotropies and the possibility to control the alignment of the liquid-crystalline semiconductor allow not only to optimize charge carrier transport, but to tune the optical property of organic thin-film devices as well. In this study, the molecular orientation in a liquid-crystalline semiconductor film is tuned by a novel blading process as well as by different annealing protocols. The altered alignment is verified by cross-polarized optical microscopy and spectroscopic ellipsometry. It is shown that a change in alignment of the liquid-crystalline semiconductor improves charge transport in single charge carrier devices profoundly. Comparing the current-voltage characteristics of single charge carrier devices with simulations shows an excellent agreement and from this an in-depth understanding of single charge carrier transport in two-terminal devices is obtained. Finally, p-i-n type organic light-emitting diodes (OLEDs) compatible with vacuum processing techniques used in state-of-the-art OLEDs are demonstrated employing liquid-crystalline host matrix in the emission layer.

U2 - 10.1038/s41598-018-19157-9

DO - 10.1038/s41598-018-19157-9

M3 - Article

SN - 2045-2322

VL - 8

JO - Scientific Reports

JF - Scientific Reports

M1 - 699

ER -

Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films: a new design space for organic light-emitting diodes

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