有机发光二极管中三重态激子的单重态转换

doi:10.7517/j.issn.1674-0475.2014.03.217

摘要/Abstract

摘要：

在OLED的研究中如何充分利用三重态激子以提高器件的电-光转换效率一直是人们关注的问题，近年来出现的经热激活逆向上转换过程获得延迟荧光的办法，使OLED的研究出现了一派崭新的前景。本文综合前人的工作对有关这一领域的研究基础，如：电子跃迁、激发态的分裂、单重态/三重态的交换能量、载流子的重合和激子的形成，以及在纯有机化合物与有机-过渡金属配合物中的电荷转移（CT）问题等，进行了较详细的讨论。

关键词: 有机发光二极管（OLED）, 热激活的延迟荧光（TADF）, 电子交换能量, 逆向的系间窜越与上转换, 电荷转移（CT）态

Abstract:

The interesting in the field of OLED study is how make the most of the application of triplet exciton for enhancing the efficiency of electro-luminescent conversion in device. Recently, the appearance of the thermo-activated delay fluorescence (TADF) which may through inverse upper conversion to obtain the delay fluorescence used in OLED, leads to a wonderful perspective in this field. In this review, several basic problems are discussed in details concluding such as the electron excitation, excited state splitting, exchange energy between singlet and triplet states, the recombination of charge carries, the formation of exciton, and the charge transfer(CT) problems in pure organic and organo-transition metal complex, etc.

Key words: organic light-emitting diode (OLED), thermo-activated delay fluorescence (TADF), exchange energy of electron, Inverse inter-system crossing and upper conversion, charge transfer (CT) state

吴世康. 有机发光二极管中三重态激子的单重态转换[J]. 影像科学与光化学, 2014, 32(3): 217-237.

WU Shikang. The Triplet State Conversion to Singlet Excited State in OLED[J]. Imaging Science and Photochemistry, 2014, 32(3): 217-237.

参考文献

[1] Tang C W,VanSlyke S A. Organic electroluminescent diodes[J]. Applied Physics Letters, 1987, 51:913.
[2] Tandon K, Ramasesha S, Mazumdar S. Electron correlation effects in electron-hole recombination in organic light emitting diodes[J]. Physical Review B, 2003, 67(4), Article ID 045109.
[3] Kondakov D Y. Role of triplet-triplet annihilation in highly efficient fluorescent devices[J]. Journal of Society for Information Display, 2009, 17(2):137.
[4] King S M, Cass M, Pintani M, Coward C, Dias F B, Monkman A P, Roberts M. The contribution of triplet-triplet annihilation to the lifetime and efficiency of fluorescent polymer organic light emitting diodes[J]. Journal of Applied Physics, 2011,109(7):Article ID 074502.
[5] Zhang Y,Forrest S R.Triplets contribute to both an increase and loss in fluorescent yield in organic light emitting diodes[J]. Physical Review Letters, 2012, 108: Article ID 267404.
[6] Yersin H, Finkenzeller W J. Triplet Emitters for Organic Light- Emitting Diodes: Basic Properties", in "Highly Efficient OLEDs with Phosphorescent Materials[M]. Edited by Hartmut Yersin, 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
[7] McGlynn S P, Azumi T , Kinoshita M. Molecular Spectroscopy of the Triplet State[M].Prentice - Hall , Englewood Cliffs, New Jersey , 1969.
[8] Turro N J. Modern MolecularPhotochemistry[M].Benjamin-Cummings, Menlo Park, Calif .,1978.31.
[9] Mataga N, Kubota T. MolecularInteractions and Electronic Spectra[M] . Marcel Dekker, New York,1970.187.
[10] Maestri M, Sandrini D,Balzani V, Chassot L, Jolliet P, von Zelewsky A. Luminescence of ortho-metallated platinum(II) complexes[J]. Chemical Physics Letters, 1985, 122(4):375.
[11] Yersin H, Donges D.Transition metal and rare earth compounds. excited states, transitions, and interactions[J]. Topics in Current Chemistry, 2001, 214:81.
[12] Glasbeek M.Excited state spectroscopy and excited state dynamics of Rh(III)and Pd(II)chelates as studied byoptically detected magnetic resonance techniques[J]. Topics in Current Chemistry, 2001, 213:96.
[13] Komada Y, Yamauchi S , Hirota N. Phosphorescence and zero-field optically detected magnetic resonance studies of the lowest excited triplet states of organometallic diimine complexes.1.Rhodium bipyridine and rhodiumphenanthroline complexes [Rh(bpy)₃]³⁺ and [Rh(phen)₃]³⁺[J]. Journal of Physical Chemistry, 1986, 90:6425.
[14] Yersin H. Triplet emitters for OLED applications. mechanisms of exciton trapping and control of emission properties[J]. Topics in Current Chemistry, 2004, 241:1-26.
[15] Yersin H,Humbs W. Spatial extensions of excited states of metal complexes. tunability by chemical variation[J]. Inorganic Chemistry, 1999, 38(25): 5820.
[16] Kondakov D Y.Role of triplet-triplet annihilation in highly efficient fluorescent devices[J]. Journal of The Society for Information Display, 17(2):137-144.
[17] Kondakov D Y.Characterization of triplet-triplet annihilation in organic light- emitting diodes based on anthracene derivatives[J]. Journal of Applied Physics, 2007, 102(11): Article ID114504.
[18] Tandon K, Ramasesha S, Mazumdar S. Electron correlation effects in electron-hole recombination in organic light emitting diodes[J]. Physical Review B, 2003, 67(4): Article ID 045109.
[19] Karabunarliev S, Bittner E R. Spin-dependent electronhole capture kinetics in luminescent conjugated polymers[J]. Physical Review Letters, 2003, 90(5): Article ID057402.
[20] Karabunarliev S,Bittner E R.Dissipative dynamics of spin-dependent electron- hole capture in conjugated polymers[J]. Journal of Chemical Physics, 2003, 119(7):3988-3995.
[21] Yin S, Chen L,Xuan P, Chen K Q, Shuai Z. Field effect on the singlet and triplet exciton formation in organic/polymeric light-emitting diodes[J]. Journal of Physical Chemistry B, 2004, 108(28):9608-9613.
[22] Barford W.Theory of singlet exciton yield in light-emitting polymers[J]. Physical Review B, 2004, 70(20):Article ID 205204.
[23] Das M, Ramasesha S, Mazumdar S. Role of electronelectron interactions on spin effects in electron-hole recombination in organic light emitting diodes[J]. Synthetic Metals, 2005, 155(2):270-273.
[24] Difley S, Beljonne D, Voorhis T V. On the singlet-triplet splitting of geminate electron-hole pairs in organic semiconductors[J]. Journal of the American Chemical Society, 2008, 130(11):3420-3427.
[25] Chen L, Zhu L, Shuai Z. Singlet-triplet splittings and their relevance to the spin-dependent exciton formation in light-emitting polymers: an EOM/CCSD study[J]. Journal of Physical Chemistry A, 2006, 110(50):13349-13354.
[26] Parker C A, Hatchard C G. Delayed fluorescence of pyrene in ethanol[J]. Transactions of the Faraday Society,1963, 59:284-295.
[27] Kepler R G, Caris J C, Avakian P,Abramson E.Triplet excitons and delayed fluorescence in anthracene crystals[J]. Physical Review Letters, 1963,10(9):400-402.
[28] Jortner J, Rice S A, Katz J L,Choi S I L.Triplet excitons in crystals of aromatic molecules[J]. Journal of Chemical Physics, 1965,42(1) :309-323.
[29] Birks J B.On the delayed fluorescence of pyrene solutions[J]. Journal of Physical Chemistry, 1963, 67(10): 2199-2200.
[30] Birks J B.The quintet state of the pyrene excimer[J]. Physics Letters A, 1967, 24(9):479-480.
[31] Perrin F.La fluorescence des solutions[J]. Annals of Physics, 1929, 12:169-275.
[32] Lewis G N, Kasha M. Phosphorescence and the triplet state[J]. Journal of the American Chemical Society, 1944, 66(12):2100-2116.
[33] Deaton J C, Switalski S C, Kondakov D Y, Young R H, Pawlik T D, Giesen D J, Harkins S B, Miller A J M, Mickenberg S F,Peters J C.E-type delayed fluorescence of a phosphine-supported Cu₂(μ-NAr₂)₂diamond core: harvesting singlet and triplet excitons in OLEDs[J]. Journal of the American Chemical Society , 2010, 132(27): 9499-9508.
[34] Endo A, Sato K, Yoshimura K, Kai T, Kawada A, Miyazaki H, Adachi C. Efficient up-conversion of triplet excitons into a singlet state and its application for organic light emitting diodes[J]. Applied Physics Letters, 2011, 98 (8): Article ID 083302.
[35] Endo A, Ogasawara M, Takahashi A, Yokoyama D, Kato Y, Adachi C.Thermally activated delayed fluorescence from Sn⁴⁺-porphyrin complexes and their application to organic light-emitting diodes -A novel mechanism for electroluminescence[J]. Advanced Materials, 2009, 21(47):4802-4806.
[36] Jenekhe S A,Osaheni J A. Excimers and exciplexes of conjugated polymers[J]. Science, 1994, 265(5173): 765-768.
[37] Itano K, Ogawa H, Shirota Y. Exciplex formation at the organic solid-state interface: yellow emission in organic light-emitting diodes using green- fluorescent tris(8-quinolinolato) aluminum and hole-transporting molecular materials with low ionization potentials[J]. Applied Physics Letters, 1998, 72(6):636-638.
[38] Cocchi M, Virgili D, Giro G , Fattori V, Marco P D, Kalinowski J,Shirota. Efficient exciplex emitting organic electroluminescent devices[J]. Applied Physics Letters, 2002, 80(13):2401-2403.
[39] Palilis L C, Makinen A J, Uchida M, Kafafi Z H.Highly efficient molecular organic light-emitting diodes based on exciplex emission[J]. Applied Physics Letters, 2003, 82(14):2209-2211.
[40] Frederichs B, Staerk H. Energy splitting between triplet and singlet exciplex states determined with E-type delayed fluorescence[J]. Chemical Physics Letters, 2008, 460(1-3):116-118.
[41] Beens H, Weller A. Application of the tyablikov-bogolyubov diagonalization method to magnetic thin films[J]. Acta Physica Polonica, 1968, 34:539-541.
[42] Wellar A. The Exciplex[M]. New York:Academic Press, 1975.
[43] Cocchi M, Virgili D, Sabatini C, Kalinowski J. Organic electroluminescence from singlet and triplet exciplexes: exciplex electrophosphorescent diode[J]. Chemical Physics Letters, 2006, 421(4-6):351-355.
[44] Morteani A C, Dhoot A S, Kim J S,Silva C, Greenham N C, Murphy C, Moons E, Cin S, Burroughes J H, Friend R H. Barrier-free electron-hole capture in polymer blend heterojunction light-emitting diodes[J]. Advanced Materials, 2003, 15(20):1708-1712.
[45] Goushi K, Yoshida K, Sato K, Adachi C.Organic lightemitting diodes employing efficient reverse intersystem crossing for triplet-to-singlet state conversion[J]. Nature Photonics, 2012, 6:253-258.
[46] Goushi K,Adachi C.Efficient organic light-emitting diodes through up-conversion from triplet to singlet excited states of exciplexes[J]. Applied Physics Letters, 2012,101:Article ID 023306.
[47] Dey R K,Chowdhury A M H, Chawdhury N,Monkman A P.Report on optical absorption, steady-state emission and time-resolved emission spectroscopy of carbazole-based conjugated polymers[J].Journal of Scientific Research, 2011, 3(1):13-24.
[48] Dias F B, Bourdakos K N, Jankus V, Moss K C , Kamtekar K T, Bhalla V, Santos J, Bryce M R,Monkman A P. Triplet harvesting with 100% efficiency by way of thermally activated delayed fluorescence in charge transfer OLED emitters[J]. Advanced Materials, 2013, doi: 10.1002/adma.201300753.
[49] Jankus V, Chiang C J, Dias F, Monkman A P. Deep blue exciplex organic light-emitting diodes with enhanced efficiency; P-type or E-type triplet conversion to singlet excitons[J]. Advanced Materials, 2013, DOI: 10.1002/adma.201203615.
[50] Su W M, Li W L, Xin Q, Su Z S, Chu B, Bi D F, He H, Niu J H. Effect of acceptor on efficiencies of exciplex-type organic light emitting diodes[J]. Applied Physics Letters, 2007, 91:043508.
[51] Endo A, Sato K, Yoshimura K, Kai T, Kawada A, Miyazaki H, Adachi C. Efficient up-conversion of triplet excitons into a singlet state and it application for organic light emitting diodes[J]. Applied Physics Letters, 2011, 98:083302.
[52] Zhang Q, Li J, Shizu K, Huang S, Hirata S, Miyazaki H, Adachi C. Design of efficient thermally activated delayed fluorescence materials for pure blue organic light emitting diodes[J]. Journal of the American Chemical Society, 2012, 134(36):14706-14709.
[53] Grabowski Z R, Rotkiewicz K, Siemiarezuk A, Cowley D J, Baumann W.Twisted intramolecular charge transfer states (TICT). A new class of excited states with a full charge separation[J]. Nouveau Journal de Chimie,1979, 3:443.
[54] Rettig W.Charge separation in excited states of decoupled systems-TICT compounds and implications regarding the development of new laser dyes and the primary process of vision and photosynthesis[J]. Angewandte Chemie International Edition,1986, 25:971.
[55] Zhang Q S, Li B, Huang S P, Nomura H, Tanaka H, Adachi C. Efficient blue organic light-emitting diodes employing thermally activated delayed fluorescence[J]. Nature, Photonics, 2014, doi:10.1038/nphoton.