logo

SCIENTIA SINICA Informationis, Volume 50 , Issue 1 : 151-162(2020) https://doi.org/10.1360/N112019-00027

Study of the microscopic mechanism of Ir(ppy)$_{3}$ regulating exciton splitting and luminescence process in Rubrene

More info
  • ReceivedJan 29, 2019
  • AcceptedMay 5, 2019
  • PublishedJan 9, 2020

Abstract

To explore the microscopic mechanism of singlet exciton splitting (${\rm~S}_{1}+{\rm~S}_{0}\to~{\rm~T}_{1}+~{\rm~T}_{1}$, STT) and luminescence in Rubrene, a phosphorescent material Ir(ppy)$_{3}$ with strong spin-orbit coupling (SOC) and green emission was selected and mixed into Rubrene thin films with different proportions to fabricate a series of luminescent devices. By measuring the magneto-electroluminescence (MEL) and current-luminescence ($I$-$B$) curves of the devices under different temperatures and currents, we found that the MEL profiles of light-emitting devices with different mixing ratios at room temperature show an STT fingerprint characteristic curve of magnetic field modulation. MEL amplitude first increases and then decreases with increased mixing ratio, whereas luminescence intensity increases monotonously. This is different from conventional Rubrene doped devices (such as mCP: $y$%Rubrene) which show STT increases with increasing concentration but with decreasing luminescence . By analyzing the singlet and triplet energy levels and emission spectra of Ir(ppy)$_{3}$ and absorption spectra of Rubrene, it can be seen that aside from Rubrene's molecular space's influence on the STT process, intersystem crossing (ISC) caused by the strong SOC of Ir(ppy)$_{3}$ and energy transfer processes between the T$_{1}$ exciton of Ir(ppy)$_{3}$ and the S$_{1}$ exciton of Rubrene are also included in the devices. The combined action of these three micro-mechanisms leads complex MEL and luminescence changes in the device, and the device's current density and working temperature also have a good regulatory effect on them. Obviously, this study helps with understanding of the microscopic process and its evolution mechanism based on Rubrene optoelectronic devices.


Funded by

国家自然科学基金(11874305)


References

[1] Podzorov V, Menard E, Borissov A. Intrinsic Charge Transport on the Surface of Organic Semiconductors. Phys Rev Lett, 2004, 93: 086602 CrossRef PubMed ADS Google Scholar

[2] Ma L, Zhang K, Kloc C. Singlet fission in Rubrene single crystal: direct observation by femtosecond pump-probe spectroscopy. Phys Chem Chem Phys, 2012, 14: 8307-8312 CrossRef PubMed ADS Google Scholar

[3] Chen Q S. Investigation of magnetic filed effects in organic light emitting devices based on Rubrebe. Dissertation for Master Degree. Chongqing: Southwest University, 2016. Google Scholar

[4] Zhang Y, Forrest S R. Triplets Contribute to Both an Increase and Loss in Fluorescent Yield in Organic Light Emitting Diodes. Phys Rev Lett, 2012, 108: 267404 CrossRef PubMed ADS Google Scholar

[5] Liu Y L, Lei Y L, Jiao Y, et al. Influence of the singlet exciton fission process at different temperatures on the magneto-electroluminescence in the Rubrene-based organic light emitting device. Sci Sin Phys Mech Astron, 2013, 43: 54--60. Google Scholar

[6] Briseno A L, Tseng R J, Ling M M. High-Performance Organic Single-Crystal Transistors on Flexible Substrates. Adv Mater, 2006, 18: 2320-2324 CrossRef Google Scholar

[7] Bai J W, Chen P, Lei Y L. Studying singlet fission and triplet fusion by magneto-electroluminescence method in singlet-triplet energy-resonant organic light-emitting diodes. Org Electron, 2014, 15: 169-174 CrossRef Google Scholar

[8] Jia W, Chen Q, Chen Y. Magneto-conductance characteristics of trapped triplet-polaron and triplet-trapped polaron interactions in anthracene-based organic light emitting diodes. Phys Chem Chem Phys, 2016, 18: 30733-30739 CrossRef PubMed ADS Google Scholar

[9] Chen Y B. Study on microscopic processes of triplet excitons in Rubrene-based organic light emitting diodes by utilizing organic magnetic field effects. Dissertation for Master Degree. Chongqing: Southwest University, 2017. Google Scholar

[10] Tang X, Hu Y, Jia W. Intersystem Crossing and Triplet Fusion in Singlet-Fission-Dominated Rubrene-Based OLEDs Under High Bias Current. ACS Appl Mater Interfaces, 2018, 10: 1948-1956 CrossRef Google Scholar

[11] Piland G B, Burdett J J, Kurunthu D. Magnetic Field Effects on Singlet Fission and Fluorescence Decay Dynamics in Amorphous Rubrene. J Phys Chem C, 2013, 117: 1224-1236 CrossRef Google Scholar

[12] Smith M B, Michl J. Singlet fission.. Chem Rev, 2010, 110: 6891-6936 CrossRef PubMed Google Scholar

[13] Chen Y B, Yuan D, Xiang J, et al. Analysis of triplet dissociation and electron scattering in the Rubrene-based devices by utilizing magneto-conductance. Sci Sin Tech, 2016, 46: 61--67. Google Scholar

[14] Baldo M A, Thompson M E, Forrest S R. High-efficiency fluorescent organic light-emitting devices using a phosphorescent sensitizer. Nature, 2000, 403: 750-753 CrossRef PubMed Google Scholar

[15] Zhang T, Xu Z, Qian L, et al. Optical and morphological investigation in interaction of dual dopants in poly (N-vinylcarzole). J Lumin, 2007, 122: 275--278. Google Scholar

[16] Kanno H, Sun Y, Forrest S R. White organic light-emitting device based on a compound fluorescent-phosphor-sensitized-fluorescent emission layer. Appl Phys Lett, 2006, 89: 143516 CrossRef Google Scholar

[17] Song D D, Zhao S L, Xu Z, et al. Study on the sensitizing effect of fac-tris(2-phenylpyridinato-N,C$^{2'}$)iridium(III) on two different fluorescent materials. Spectrosc Spectr Anal, 2009, 29: 2626--2629. Google Scholar

[18] Zhao Y, Zhu L, Chen J. Improving color stability of blue/orange complementary white OLEDs by using single-host double-emissive layer structure: Comprehensive experimental investigation into the device working mechanism. Org Electron, 2012, 13: 1340-1348 CrossRef Google Scholar

[19] Chen P, Lei Y L, Song Q L. Control of magnetoconductance through modifying the amount of dissociated excited states in tris-(8-hydroxyquinoline) aluminum-based organic light-emitting diodes. Appl Phys Lett, 2010, 96: 203303 CrossRef ADS Google Scholar

[20] Huang W, Mi B X, Gao Z Q. Organic Electronics. Beijing: Science Press, 2011. Google Scholar

[21] Xu H H, Xu Z, Zhang F J, et al. Phosphorescent effect of Ir(ppy)$_{3~}$on the luminescent characteristic of Rubrene. Spectrosc Spec Anal, 2008, 28: 1608--1611. Google Scholar

[22] Li Y R, Zhao S L, Yang S P, et al. Properties of energy transfer in two host materials doped with Ir(ppy)$_{3}$ and Rubrene. Spectrosc Spec Anal, 2009, 29: 1--5. Google Scholar

[23] Jiang W L, Ding G Y, Wang J, et al. Highly efficient white phosphorescent organic light-emitting devices using an electron/exciton blocker. J Optoelectron Laser, 2008, 19: 595--598. Google Scholar

  • Figure 1

    (Color online) The device optical and electronic properties. (a) The diagram of device structure; (b) the $I$-$V$ curves of devices, the inset is the molecular structures; (c) the normalized PL spectra of Ir(ppy)$_3$ and Rubrene films;protect łinebreak (d) the brightness intensity of devices with different concentrations under various injection currents at room temperature

  • Figure 2

    (Color online)The MEL response curves of the reference device and the Rubrene: 10%Ir(ppy)$_3$device at different temperatures and injection currents. (a)–(d) Rubrene: 10%Ir(ppy)$_3$ devices; (e)–(h) reference devices

  • Figure 3

    (Color online) (a) Temperature-dependent MEL curves of the Rubrene:10%Ir(ppy)$_{3}$ device at 10 $\mu~$A;protect łinebreak (b) temperature-dependentMEL$_{\rm~HFE}$ values of the reference device and the Rubrene:10%Ir(ppy)$_{3}$ device

  • Figure 4

    (Color online) (a) Mixing concentrations-dependent MEL curves ofdevice Rubrene: $x$%Ir(ppy)$_{3}$ at room temperature when the current is 10$\mu~$A; (b) mixing concentrations-dependent MEL$_{\rm~HFE}$ value underdifferent currents at room temperature; (c) mixing concentrations-dependentMEL curves of device Rubrene: $x$%Ir(ppy)$_{3}$ at 20 K when the current is10 $\mu~$A; (d) mixing concentrations-dependent MEL$_{\rm~HFE}$ value underdifferent temperature at 10 $\mu~$A

  • Figure 5

    (Color online) (a) The microscopic processes of devices; (b) theschematic of microscopic process of exciton and polaron betweenIr(ppy)$_{3}$ and Rubrene at low concentration mixing; (c) the MEL$_{B~=~300}$ values and brightness intensity of devices with various differentconcentrations at room temperature and the injection current of 10 $\mu~$A;(d) the schematic of microscopic process of exciton and polaron betweenIr(ppy)$_{3}$ and Rubrene at high concentration mixing. The circlesrepresent Rubrene, and the triangles represent Ir(ppy)$_{3~}$ in (b) and (d)

Copyright 2020  CHINA SCIENCE PUBLISHING & MEDIA LTD.  中国科技出版传媒股份有限公司  版权所有

京ICP备14028887号-23       京公网安备11010102003388号