- Physical Review Journals
All JournalsPhysics Magazine

Physical Review Applied

Reuse & Permissions

It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 4.0 International license. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author(s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder directly for these figures.

Export citation

Export citation

Choose format for download:

Download Citation
  • Open Access

Sweet spot of energy-level alignment in hyperfluorescent organic light-emitting diodes

Rishabh Saxena1,2,*,†, Giacomo Cotelli1,3,*, Kleitos Stavrou4, Engin Torun3, Larissa G. Franca4, Andrew P. Monkman4, Stefano Gottardi3, and Anna Köhler1,‡

  • *These authors contributed equally to this work
  • †Contact author: saxenar@mpip-mainz.mpg.de
  • ‡Contact author: anna.koehler@uni-bayreuth.de
PDF

Phys. Rev. Applied 24, 024064 – Published 26 August, 2025

DOI: https://doi.org/10.1103/k967-sr56

Abstract

We investigate loss mechanisms in hyperfluorescent organic light-emitting diodes (HF-OLEDs) with the emissive layer consisting of a host, a thermally activated delayed fluorescence (TADF) sensitizer, and a terminal emitter. We focus on understanding how the relative energy levels between the TADF sensitizer and terminal emitter impact device efficiency and roll-off through the formation and subsequent dissociation of an intermolecular state. Using a combined experimental and kinetic Monte Carlo (KMC) simulation-based approach, we analyzed HF-OLEDs incorporating either multiresonant (MR) or fluorescent (non-MR) terminal emitters. We find that selecting terminal emitters with ionization potential and electron affinity values that position the intermolecular state at least 150 meV above the singlet energy of the terminal emitter effectively suppresses the losses due to exciton dissociation. Furthermore, we show that using the MR emitter, which exhibits reverse intersystem crossing (RISC), significantly reduces residual triplet-related losses compared with the non-MR emitter. This further mitigates exciton dissociation losses, thereby improving the external quantum efficiency (EQE). These findings provide clear guidelines for selecting terminal emitters and optimizing energy level alignment to address intermolecular state-related loss pathways in HF-OLEDs.

View figure in article

Physics Subject Headings (PhySH)

Article Text

Supplemental Material

References (63)

  1. M. A. Baldo, D. F. O’Brien, Y. You, A. Shoustikov, S. Sibley, M. E. Thompson, and S. R. Forrest, Highly efficient phosphorescent emission from organic electroluminescent devices, Nature 395, 151 (1998).
  2. H. Uoyama, K. Goushi, K. Shizu, H. Nomura, and C. Adachi, Highly efficient organic light-emitting diodes from delayed fluorescence, Nature 492, 234 (2012).
  3. U. Monkowius and H. Yersin. Complexes with small singlet-triplet energy separations for use in opto-electronic components (singlet harvesting effect). DE 10 2008 033 563 A1, 2008.
  4. A. Endo, M. Ogasawara, A. Takahashi, D. Yokoyama, Y. Kato, and C. Adachi, Thermally activated delayed fluorescence from Sn(4+)-porphyrin complexes and their application to organic light emitting diodes–a novel mechanism for electroluminescence, Adv. Mater. 21, 4802 (2009).
  5. A. Monkman, Why do we still need a stable long lifetime deep blue OLED emitter?, ACS Appl. Mater. Interfaces 14, 20463 (2022).
  6. T. Hatakeyama, K. Shiren, K. Nakajima, S. Nomura, S. Nakatsuka, K. Kinoshita, J. Ni, Y. Ono, and T. Ikuta, Ultrapure blue thermally activated delayed fluorescence molecules: Efficient HOMO-LUMO separation by the multiple resonance effect, Adv. Mater. 28, 2777 (2016).
  7. H. Nakanotani, T. Higuchi, T. Furukawa, K. Masui, K. Morimoto, M. Numata, H. Tanaka, Y. Sagara, T. Yasuda, and C. Adachi, High-efficiency organic light-emitting diodes with fluorescent emitters, Nat. Commun. 5, 4016 (2014).
  8. H. Abroshan, Y. Zhang, X. Zhang, C. Fuentes-Hernandez, S. Barlow, V. Coropceanu, S. R. Marder, B. Kippelen, and J. L. Brédas, Thermally activated delayed fluorescence sensitization for highly efficient blue fluorescent emitters, Adv. Funct. Mater. 30, 2005898 (2020).
  9. J. Adachi, H. Kakizoe, P. K. D. Tsang, and A. Endo, 10.1: Invited paper: Hyperfluorescence™; a game changing technology of OLED display, SID Symp. Dig. Tech. Pap. 50, 95 (2019).
  10. T. Furukawa, H. Nakanotani, M. Inoue, and C. Adachi, Dual enhancement of electroluminescence efficiency and operational stability by rapid upconversion of triplet excitons in OLEDs, Sci. Rep. 5, 8429 (2015).
  11. Y. Wada, H. Nakagawa, S. Matsumoto, Y. Wakisaka, and H. Kaji, Organic light emitters exhibiting very fast reverse intersystem crossing, Nat. Photonics 14, 643 (2020).
  12. Y. Gawale, R. Ansari, K. R. Naveen, and J. H. Kwon, Forthcoming hyperfluorescence display technology: relevant factors to achieve high-performance stable organic light emitting diodes, Front. Chem. 11, 1211345 (2023).
  13. K. R. Naveen, P. Palanisamy, M. Y. Chae, and J. H. Kwon, Multiresonant TADF materials: triggering the reverse intersystem crossing to alleviate the efficiency roll-off in OLEDs, Chem. Commun. 59, 3685 (2023).
  14. C.-Y. Chan, M. Tanaka, Y.-T. Lee, Y.-W. Wong, H. Nakanotani, T. Hatakeyama, and C. Adachi, Stable pure-blue hyperfluorescence organic light-emitting diodes with high-efficiency and narrow emission, Nat. Photonics 15, 203 (2021).
  15. S. O. Jeon, K. H. Lee, J. S. Kim, S.-G. Ihn, Y. S. Chung, J. W. Kim, H. Lee, S. Kim, H. Choi, and J. Y. Lee, High-efficiency, long-lifetime deep-blue organic light-emitting diodes, Nat. Photonics 15, 208 (2021).
  16. K. Stavrou, L. G. Franca, A. Danos, and A. P. Monkman, Key requirements for ultraefficient sensitization in hyperfluorescence organic light-emitting diodes, Nat. Photonics 18, 554 (2024).
  17. K. Stavrou, S. Madayanad Suresh, D. Hall, A. Danos, N. A. Kukhta, A. M. Z. Slawin, S. Warriner, D. Beljonne, Y. Olivier, A. Monkman, et al., Emission and absorption tuning in TADF B,N-doped heptacenes: Toward ideal-blue hyperfluorescent OLEDs, Adv. Opt. Mater. 10, 2200688 (2022).
  18. A. Köhler and H. Bässler, Electronic Processes in Organic Semiconductors: An Introduction (John Wiley & Sons, Weinheim, 2015).
  19. Y. T. Lee, C. Y. Chan, M. Tanaka, M. Mamada, U. Balijapalli, Y. Tsuchiya, H. Nakanotani, T. Hatakeyama, and C. Adachi, Investigating HOMO energy levels of terminal emitters for realizing high-brightness and stable TADF-assisted fluorescence organic light-emitting diodes, Adv. Electron. Mater. 7, 2001090 (2021).
  20. K. Stavrou, A. Danos, T. Hama, T. Hatakeyama, and A. Monkman, Hot vibrational states in a high-performance multiple resonance emitter and the effect of excimer quenching on organic light-emitting diodes, ACS Appl. Mater. Interfaces 13, 8643 (2021).
  21. J. J. M. Halls, J. Cornil, D. A. dos Santos, R. Silbey, D.-H. Hwang, A. B. Holmes, J. L. Brédas, and R. H. Friend, Charge- and energy-transfer processes at polymer/polymer interfaces: A joint experimental and theoretical study, Phys. Rev. B 60, 5721 (1999).
  22. S. Gottardi, M. Barbry, R. Coehoorn, and H. van Eersel, Efficiency loss processes in hyperfluorescent OLEDs: A kinetic Monte Carlo study, Appl. Phys. Lett. 114, 073301 (2019).
  23. M. Deussen, M. Scheidler, and H. Bässler, Electric field-induced photoluminescence quenching in thin-film light emitting diodes based on poly(phenyl-p-phenylene vinylene), Synth. Met. 73, 123 (1995).
  24. S. Haneder, E. Da Como, J. Feldmann, M. M. Rothmann, P. Strohriegl, C. Lennartz, O. Molt, I. Münster, C. Schildknecht, and G. Wagenblast, Effect of electric field on coulomb-stabilized excitons in host/guest systems for deep-blue electrophosphorescence, Adv. Funct. Mater. 19, 2416 (2009).
  25. C. Murawski, K. Leo, and M. C. Gather, Efficiency roll-off in organic light-emitting diodes, Adv. Mater. 25, 6801 (2013).
  26. R. Coehoorn, H. van Eersel, P. Bobbert, and R. Janssen, Kinetic Monte Carlo study of the sensitivity of OLED efficiency and lifetime to materials parameters, Adv. Funct. Mater. 25, 2024 (2014).
  27. A. Ligthart, X. de Vries, L. Zhang, M. C. W. M. Pols, P. A. Bobbert, H. van Eersel, and R. Coehoorn, Effect of triplet confinement on triplet–triplet annihilation in organic phosphorescent host–guest systems, Adv. Funct. Mater. 28, 1804618 (2018).
  28. M. Mesta, H. van Eersel, R. Coehoorn, and P. A. Bobbert, Kinetic Monte Carlo modeling of the efficiency roll-off in a multilayer white organic light-emitting device, Appl. Phys. Lett. 108, 133301 (2016).
  29. H. van Eersel, P. A. Bobbert, R. A. J. Janssen, and R. Coehoorn, Monte Carlo study of efficiency roll-off of phosphorescent organic light-emitting diodes: Evidence for dominant role of triplet-polaron quenching, Appl. Phys. Lett. 105, 143303 (2014).
  30. H. van Eersel, P. A. Bobbert, and R. Coehoorn, Kinetic Monte Carlo study of triplet-triplet annihilation in organic phosphorescent emitters, J. Appl. Phys. 117, 115502 (2015).
  31. F. Yang, H. van Eersel, J. Wang, Q. Niu, P. A. Bobbert, R. Coehoorn, F. Liu, and G. Zhou, Dilution-induced current-density increase in disordered organic semiconductor devices: A kinetic Monte Carlo study, Phys. Rev. Appl. 21, 014050 (2024).
  32. See Supplemental Material at http://link.aps.org/supplemental/10.1103/k967-sr56 for parameter optimization (Sec. S1), photophysical data (Sec. S2), discussion on the effect of the co-evaporated α-NPD:mCBP (1:1) layer (Sec. S3), further OLED results (Sec. S4), further simulation results (Sec. S5), further photophysical data (Sec. S6), and energies of the CT states between different materials (Sec. S7).
  33. Bumblebee is currently provided by SCM, Amsterdam, The Netherlands, https://www.scm.com/oled/oled-workflows.
  34. C. Hauenstein, S. Gottardi, E. Torun, R. Coehoorn, and H. van Eersel, Identification of OLED degradation scenarios by kinetic Monte Carlo simulations of lifetime experiments, Front. Chem. 9, 823210 (2021).
  35. X. de Vries, P. Friederich, W. Wenzel, R. Coehoorn, and P. A. Bobbert, Full quantum treatment of charge dynamics in amorphous molecular semiconductors, Phys. Rev. B 97, 075203 (2018).
  36. R. Saxena, T. Meier, S. Athanasopoulos, H. Bässler, and A. Köhler, Kinetic Monte Carlo study of triplet-triplet annihilation in conjugated luminescent materials, Phys. Rev. Appl. 14, 034050 (2020).
  37. R. Saxena, V. R. Nikitenko, I. I. Fishchuk, Y. V. Burdakov, Y. V. Metel, J. Genoe, H. Bässler, A. Köhler, and A. Kadashchuk, Role of the reorganization energy for charge transport in disordered organic semiconductors, Phys. Rev. B 103, 165202 (2021).
  38. P. K. Watkins, A. B. Walker, and G. L. B. Verschoor, Dynamical Monte Carlo modelling of organic solar cells: The dependence of internal quantum efficiency on morphology, Nano Lett. 5, 1814 (2005).
  39. M. Mesta, M. Carvelli, R. J. de Vries, H. van Eersel, J. J. van der Holst, M. Schober, M. Furno, B. Lussem, K. Leo, P. Loebl, et al., Molecular-scale simulation of electroluminescence in a multilayer white organic light-emitting diode, Nat. Mater. 12, 652 (2013).
  40. Y. Shen and N. C. Giebink, Monte Carlo simulations of nanoscale electrical inhomogeneity in organic light-emitting diodes and its impact on their efficiency and lifetime, Phys. Rev. Appl. 4, 054017 (2015).
  41. T. Hua, L. Zhan, N. Li, Z. Huang, X. Cao, Z. Xiao, S. Gong, C. Zhou, C. Zhong, and C. Yang, Heavy-atom effect promotes multi-resonance thermally activated delayed fluorescence, Chem. Eng. J. 426, 131169 (2021).
  42. A. Stankevych, R. Saxena, J. Grüne, S. Lulei, A. Sperlich, S. Athanasopoulos, A. Vakhnin, P. Sahay, W. Brütting, V. Dyakonov, et al., Charge-carrier photogeneration in single-component organic carbazole-based semiconductors via low excitation power triplet-triplet annihilation, Phys. Rev. Appl. 20, 064029 (2023).
  43. T. A. Lin, T. Chatterjee, W. L. Tsai, W. K. Lee, M. J. Wu, M. Jiao, K. C. Pan, C. L. Yi, C. L. Chung, K. T. Wong, et al., Sky-blue organic light emitting diode with 37% external quantum efficiency using thermally activated delayed fluorescence from spiroacridine-triazine hybrid, Adv. Mater. 28, 6976 (2016).
  44. H. Yoshida and K. Yoshizaki, Electron affinities of organic materials used for organic light-emitting diodes: A low-energy inverse photoemission study, Org. Electron. 20, 24 (2015).
  45. M. Hasan, S. Saggar, A. Shukla, F. Bencheikh, J. Sobus, S. K. M. McGregor, C. Adachi, S. C. Lo, and E. B. Namdas, Probing polaron-induced exciton quenching in TADF based organic light-emitting diodes, Nat. Commun. 13, 254 (2022).
  46. B. A. Naqvi, M. Schmid, E. Crovini, P. Sahay, T. Naujoks, F. Rodella, Z. Zhang, P. Strohriegl, S. Brase, E. Zysman-Colman, et al., What controls the orientation of TADF emitters?, Front. Chem. 8, 750 (2020).
  47. A. Stankevych, R. Saxena, A. Vakhnin, F. May, N. Kinaret, D. Andrienko, J. Genoe, H. Bässler, A. Köhler, and A. Kadashchuk, Monitoring the charge-carrier-occupied density of states in disordered organic semiconductors under nonequilibrium conditions using thermally stimulated luminescence spectroscopy, Phys. Rev. Appl. 19, 054007 (2023).
  48. A. Stankevych, A. Vakhnin, D. Andrienko, L. Paterson, J. Genoe, I. Fishchuk, H. Bässler, A. Köhler, and A. Kadashchuk, Density of states of OLED host materials from thermally stimulated luminescence, Phys. Rev. Appl. 15, 044050 (2021).
  49. S. G. Ihn, N. Lee, S. O. Jeon, M. Sim, H. Kang, Y. Jung, D. H. Huh, Y. M. Son, S. Y. Lee, M. Numata, et al., An alternative host material for long-lifespan blue organic light-emitting diodes using thermally activated delayed fluorescence, Adv. Sci. (Weinh) 4, 1600502 (2017).
  50. Y. Wada, K. Shizu, S. Kubo, T. Fukushima, T. Miwa, H. Tanaka, C. Adachi, and H. Kaji, Highly efficient solution-processed host-free organic light-emitting diodes showing an external quantum efficiency of nearly 18% with a thermally activated delayed fluorescence emitter, Appl. Phys. Express 9, 032102 (2016).
  51. V. Jankus, C. J. Chiang, F. Dias, and A. P. Monkman, Deep blue exciplex organic light-emitting diodes with enhanced efficiency; P-type or E-type triplet conversion to singlet excitons?, Adv. Mater. 25, 1455 (2013).
  52. H.-F. Chen, S.-J. Yang, Z.-H. Tsai, W.-Y. Hung, T.-C. Wang, and K.-T. Wong, 1,3,5-Triazine derivatives as new electron transport–type host materials for highly efficient green phosphorescent OLEDs, J. Mater. Chem. 19, 8112 (2009).
  53. H. Abroshan, V. Coropceanu, and J.-L. Brédas, Hyperfluorescence-based emission in purely organic materials: Suppression of energy-loss mechanisms via alignment of triplet excited states, ACS Mater. Lett. 2, 1412 (2020).
  54. D. Sun, E. Duda, X. Fan, R. Saxena, M. Zhang, S. Bagnich, X. Zhang, A. Köhler, and E. Zysman-Colman, Thermally activated delayed fluorescent dendrimers that underpin high-efficiency host-free solution-processed organic light-emitting diodes, Adv. Mater. 34, 2110344 (2022).
  55. D. Sun, R. Saxena, X. Fan, S. Athanasopoulos, E. Duda, M. Zhang, S. Bagnich, X. Zhang, E. Zysman-Colman, and A. Köhler, Regiochemistry of donor dendrons controls the performance of thermally activated delayed fluorescence dendrimer emitters for high efficiency solution-processed organic light-emitting diodes, Adv. Sci. (Weinh) 9, 2201470 (2022).
  56. K. Stavrou, L. G. Franca, and A. P. Monkman, Photophysics of TADF guest-host systems: Introducing the idea of hosting potential, ACS Appl. Electron. Mater. 2, 2868 (2020).
  57. Y.-H. Yu, C.-H. Huang, J.-M. Yeh, and P.-T. Huang, Effect of methyl substituents on the N-diaryl rings of anthracene-9,10-diamine derivatives for OLEDs applications, Org. Electron. 12, 694 (2011).
  58. S. Sem, S. Jenatsch, P. Sahay, S. Züfle, M. Schmid, W. Brütting, and B. Ruhstaller, Detailed electro-optical modeling of thermally-activated delayed fluorescent OLEDs with different host-guest concentrations, Org. Electron. 107, 106553 (2022).
  59. T. Higuchi, H. Nakanotani, and C. Adachi, High-efficiency white organic light-emitting diodes based on a blue thermally activated delayed fluorescent emitter combined with green and red fluorescent emitters, Adv. Mater. 27, 2019 (2015).
  60. T. A. Madison, A. G. Gagorik, and G. R. Hutchison, Charge transport in imperfect organic field effect transistors: Effects of charge traps, J. Phys. Chem. C 116, 11852 (2012).
  61. A. Hofmann, M. Schmid, and W. Brütting, The many facets of molecular orientation in organic optoelectronics, Adv. Opt. Mater. 9, 2101004 (2021).
  62. A. Ligthart, T. D. G. Nevels, C. H. L. Weijtens, P. A. Bobbert, and R. Coehoorn, Mechanistic description of the efficiency loss in organic phosphorescent host–guest systems due to triplet-polaron quenching, Org. Electron. 91, 106058 (2021).
  63. J. Benduhn, K. Tvingstedt, F. Piersimoni, S. Ullbrich, Y. Fan, M. Tropiano, K. A. McGarry, O. Zeika, M. K. Riede, C. J. Douglas, et al., Intrinsic nonradiative voltage losses in fullerene-based organic solar cells, Nat. Energy 2, 17053 (2017).

Outline

Information

Phys. Rev. Applied 24, 024064– Published 26 August, 2025
  • Received 18 March 2025
  • Revised 22 May 2025
  • Accepted 18 July 2025
Crossmark - Check for updates button
Creative Commons Logo

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Sign In to Your Journals Account

Filter

Filter

Article Lookup

Enter a citation