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Menghrajani KS, Vasista AB, Tan WJ, Thomas PA, Herrera F, Barnes WL. Molecular Strong Coupling and Cavity Finesse. J Phys Chem Lett 2024; 15:7449-7457. [PMID: 39008808 DOI: 10.1021/acs.jpclett.4c00782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/17/2024]
Abstract
Molecular strong coupling offers exciting prospects in physics, chemistry, and materials science. While attention has been focused on developing realistic models for the molecular systems, the important role played by the entire photonic mode structure of the optical cavities has been less explored. We show that the effectiveness of molecular strong coupling may be critically dependent on cavity finesse. Specifically we only see emission associated with a dispersive lower polariton for cavities with sufficient finesse. By developing an analytical model of cavity photoluminescence in a multimode structure we clarify the role of finite-finesse in polariton formation and show that lowering the finesse reduces the extent of the mixing of light and matter in polariton states. We suggest that the detailed nature of the photonic modes supported by a cavity will be as important in developing a coherent framework for molecular strong coupling as the inclusion of realistic molecular models.
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Affiliation(s)
- Kishan S Menghrajani
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
| | - Adarsh B Vasista
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
| | - Wai Jue Tan
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
| | - Philip A Thomas
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
| | - Felipe Herrera
- Department of Physics, Universidad de Santiago de Chile, Av. Victor Jara 3493, Santiago 9170124, Chile
- Millennium Institute for Research in Optics, Concepción 750, Chile
| | - William L Barnes
- Department of Physics and Astronomy, Stocker Road, University of Exeter, Devon EX4 4QL, United Kingdom
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Keum CM, Liu S, Al-Shadeedi A, Kaphle V, Callens MK, Han L, Neyts K, Zhao H, Gather MC, Bunge SD, Twieg RJ, Jakli A, Lüssem B. Tuning charge carrier transport and optical birefringence in liquid-crystalline thin films: A new design space for organic light-emitting diodes. Sci Rep 2018; 8:699. [PMID: 29335503 PMCID: PMC5768873 DOI: 10.1038/s41598-018-19157-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 12/12/2017] [Indexed: 11/09/2022] Open
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.
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Affiliation(s)
- Chang-Min Keum
- Department of Physics, Kent State University, Kent, OH, 44242, USA.
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom.
| | - Shiyi Liu
- Department of Physics, Kent State University, Kent, OH, 44242, USA
| | - Akram Al-Shadeedi
- Department of Physics, Kent State University, Kent, OH, 44242, USA
- Department of physics, University of Baghdad, Al-Jadriya, Baghdad, 10071, Iraq
| | - Vikash Kaphle
- Department of Physics, Kent State University, Kent, OH, 44242, USA
| | - Michiel Koen Callens
- Department of Electronics and Information Systems, Ghent University, Ghent, B-9000, Belgium
| | - Lu Han
- Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Kristiaan Neyts
- Department of Electronics and Information Systems, Ghent University, Ghent, B-9000, Belgium
| | - Hongping Zhao
- Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, OH, 44106, USA
| | - Malte C Gather
- Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom
| | - Scott D Bunge
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, 44242, USA
| | - Robert J Twieg
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH, 44242, USA
| | - Antal Jakli
- Liquid Crystal Institute, Kent State University, Kent, OH, 44242, USA
| | - Björn Lüssem
- Department of Physics, Kent State University, Kent, OH, 44242, USA
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Pan Z, Rawat N, Cour I, Manning L, Headrick RL, Furis M. Polarization-resolved spectroscopy imaging of grain boundaries and optical excitations in crystalline organic thin films. Nat Commun 2015; 6:8201. [PMID: 26365682 PMCID: PMC4579592 DOI: 10.1038/ncomms9201] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 07/24/2015] [Indexed: 12/03/2022] Open
Abstract
Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to submicron grain sizes and the presence of numerous structural defects, disorder and grain boundaries. Here we report on the results of combined linear dichroism (LD)/ polarization-resolved photoluminescence (PL) scanning microscopy experiments that simultaneously probe the excitonic radiative recombination and the molecular ordering in solution-processed metal-free phthalocyanine crystalline thin films with macroscopic grain sizes. LD/PL images reveal the relative orientation of the singlet exciton transition dipoles at the grain boundaries and the presence of a localized electronic state that acts like a barrier for exciton diffusion across the grain boundary. We also show how this energy barrier can be entirely eliminated through the optimization of deposition parameters that results in films with large grain sizes and small-angle boundaries. These studies open an avenue for exploring the influence of long-range order on exciton diffusion and carrier transport. In-depth understanding of organic crystalline semiconductor thin films is critical for the development of many electronic and photonic devices. Here, the authors use combined linear dichroism and polarization-resolved photoluminescence scanning microscopy to unveil the nature of excited states in such systems.
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Affiliation(s)
- Z Pan
- Department of Physics, Materials Science Program, University of Vermont, Burlington, Vermont 05405, USA
| | - N Rawat
- Department of Physics, Materials Science Program, University of Vermont, Burlington, Vermont 05405, USA
| | - I Cour
- Department of Physics, Materials Science Program, University of Vermont, Burlington, Vermont 05405, USA
| | - L Manning
- Department of Physics, Materials Science Program, University of Vermont, Burlington, Vermont 05405, USA
| | - R L Headrick
- Department of Physics, Materials Science Program, University of Vermont, Burlington, Vermont 05405, USA
| | - M Furis
- Department of Physics, Materials Science Program, University of Vermont, Burlington, Vermont 05405, USA
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Maibohm C, Rastedt M, Kutscher F, Frey O, Beckhaus R, Rubahn HG, Al-Shamery K. Optical waveguiding and temperature dependent photoluminescence of nanotubulars grown from molecular building blocks. Chem Phys Lett 2013. [DOI: 10.1016/j.cplett.2013.10.039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Ahn TS, Al-Kaysi RO, Müller AM, Wentz KM, Bardeen CJ. Self-absorption correction for solid-state photoluminescence quantum yields obtained from integrating sphere measurements. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2007; 78:086105. [PMID: 17764365 DOI: 10.1063/1.2768926] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
A new method is presented for analyzing the effects of self-absorption on photoluminescence integrating sphere quantum yield measurements. Both the observed quantum yield and luminescence spectrum are used to determine the self-absorption probability, taking into account both the initial emission and subsequent absorption and reemission processes. The analysis is experimentally validated using the model system of the laser dye perylene red dispersed in a polymer film. This approach represents an improvement over previous methods that tend to overestimate the true quantum yield, especially in cases with high sample absorbance or quantum yield values.
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Affiliation(s)
- Tai-Sang Ahn
- Department of Chemistry, University of California, Riverside, CA 92521, USA
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