Electroluminescent polymers: Materials, physics and device engineering

Current Opinion in Solid State and Materials Science

Volumn 1, Issue 6, 1996, Pages 789-797

  Bradley, Donal ^a  

^a UNIVERSITY OF SHEFFIELD   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000903144     PISSN: 13590286     EISSN: None     Source Type: Journal    
DOI: 10.1016/S1359-0286(96)80103-3     Document Type: Article

References (68)

1. Burroughes JH, Bradley DDC, Brown AR, Marks RN, Mackay KD, Friend RH, Burn PL, Holmes AB: Light-emitting diodes based on conjugated polymers. Nature 1990, 347:539-541.
2. Greenham NC, Samuel IDW, Hayes GR, Phillips RT, Kessener YARR, Moratti SC, Holmes AB, Friend RH: Measurement of absolute photoluminescence quantum efficiencies in conjugated polymers. Chem Phys Lett 1995, 241:89-96. Describes the measurement of quantum efficiencies within an integrating sphere and reports results for a range of widely studied materials.
3. ••]).
4. Greenham NC, Bradley DDC, Friend RH: Angular dependence of the emission from a conjugated polymer light-emitting diode: implications for efficiency calculations. Adv Mater 1994, 6:491-494.
5. Yang Y, Westerweele E, Zhang C, Smith P, Heeger AJ: Enhanced performance of polymer light-emitting diodes using high-surface area polyaniline network electrodes. J Appl Phys 1995, 77:694-698. The use of conducting polyaniline as a transparent anode material enables much more ready integration of polymer EL devices onto flexible or shaped substrates (see [61]). It is also beneficial in lowering threshold voltages and enhancing brightness and stability (see also [9,11,14•,34•]).
6. Buchwald E, Meier M, Karg S, Pösch P, Schmidt H-W, Strohriegl P, Rieb W, Schwoerer M: Enhanced efficiency of polymer light emitting diodes utilizing oxadiazole polymers. Adv Mater 1995, 7:839-842.
7. Proceedings ICSM'96, Salt Lake City, Utah, USA, August 1996. Synth Met 1996, in press.
8. 2 have been achieved.
9. Karg S, Scott JC, Salem JR, Angelopoulos M: Increased brightness and lifetime of polymer light-emitting diodes with polyaniline electrodes. Synth Met 1996, 80:111-117.
10. Bradley DDC: Conjugated polymer electroluminescence. Synth Met 1993, 54:401-415.
11. Yang Y, Pei Q: Electron injection polymer for polymer light-emitting diodes. J Appl Phys 1995, 77:4807-4809.
12. Rieb W: [Habilitation Thesis] Bayreuth, Germany: University of Bayreuth; 1996.
13. Scott JC, Kaufman JH, Brock PJ, DiPietro R, Salem J, Goitia JA: Degradation and failure of MEH-PPV light-emitting diodes. J Appl Phys 1996, 79:2745-2751. Highlights the importance of oxygen diffusion from ITO as a source of oxidative degradation and formation of localized electrical shorts that coalesce and cause ultimate device failure.
14. Yang Y, Pei Q, Heeger AJ: Efficient blue polymer light-emitting diodes from a series of soluble poly(paraphenylene)s. J Appl Phys 1996, 79:934-939. Reports an external quantum efficiency of 3% in the blue.
15. Greenham NC, Moratti SC, Bradley DDC, Friend RH, Holmes AB: Efficient light-emitting diodes based on polymers with high electron affinities. Nature 1993, 365:628-631.
16. Salaneck WR, Brédas J-L: The metal-on-polymer interface in polymer light emitting diodes. Adv Mater 1996, 8:48-52. Salaneck and Brédas review the experimental and theoretical understanding of metal-on-polymer interfaces.
17. Konstadinidis K, Papadimitrakopoulos F, Galvin M, Opila RL: In-situ X-ray photoelectron spectroscopy study of aluminium/poly(p-phenylenevinylene) interfaces. J Appl Phys 1995, 77:5643-5646.
18. •]).
19. Rikken GLJA, Kessener YARR, Braun D, Staring EGJ, Demandt R: Internal photoemission studies of metal/polymer interfaces. Synth Met 1994, 67:115-119.
20. Campbell IH, Hagler TW, Smith DL, Ferraris JP: Direct measurement of conjugated polymer electronic excitation energies using metal/polymer/metal structures. Phys Rev Lett 1996, 76:1900-1903. This paper describes a new technique using electroabsorption spectroscopy that has been developed to study the built-in-field in polymer diodes. Internal photoemission results are also reported.
21. Blom PWM, De Jong MJM, Vleggaar JJM: Electron and hole transport in poly(p-phenylenevinylene) devices. Appl Phys Lett 1996, 68:3308-3310. Illustrates the imbalance in electron and hole transport in a typical PPV based polymer and relates this imbalance to trap state effects.
22. Meyer H, Haarer D, Naarmann H, Hörhold H-H: Trap distribution for charge carriers in poly(paraphenylenevinylene) (PPV) and its substituted derivative DPOP-PPV. Phys Rev 1995, 852:2587-2598. Deduces information on trap states and their energetic distribution from photocurrent measurements.
23. Burrows PE, Shen Z, Bulovic V, McCarty DM, Forrest SR, Cronin JA, Thompson ME: Relationship between electroluminescence and current transport in organic light-emitting diodes. J Appl Phys 1996, 79:7991-8006. The authors describe a detailed model for the diode characteristics of devices fabricated with sublimed organic materials. They emphasize the importance of trap states in controlling device behaviour and offer an alternative explanation of device operation to the previously proposed Fowler-Nordheim tunnelling description. References are given to previous studies of this problem in polymer devices.
24. Campbell IH, Joswick MD, Parker ID: Direct measurement of the internal electric field distribution in a multilayer organic light-emitting diode. Appl Phys Lett 1995, 67:3171-3173. Experimental verification of the redistribution of field within a multilayer EL device.
25. Greenham NC, Friend RH: Semiconductor device physics of conjugated polymers. In Solid State Physics, Vol. 49. Edited by Ehrenreich H. New York: Academic Press; 1995:1-149. A recent review covering physics and operation of a variety of conjugated polymer devices.
26. 3 groups as electron-withdrawing substituents to increase electron affinity.
27. Li X-C, Cacialli F, Giles M, Grüner J, Friend RH, Holmes AB, Moratti SC, Yong TM: Charge transport polymers for light emitting diodes. Adv Mater 1995, 7:898-900.
28. Murata H, Hirano H, Yamanaka T, Ukishima S: A novel fabrication technique and new conjugated polymers for multilayer polymer light emitting diodes. Trends Polymer Science 1996, in press. This paper details the fabrication of a series of poly(oxadiazole)s via a chemical vapour deposition polymerization. Such an approach is compatible with sublimation deposition of low molecular weight organic compounds and also vapour phase deposition of the ITO anode and metal cathodes. It is well suited to sequential depositions in multi-layer devices and avoids problems faced with solution deposition (see also [37,38]).
29. Strukelj M, Papadimitrakopolous F, Miller TM, Rothberg U: Design and application of electron-transporting organic materials. Science 1995, 267:1969-1972. Describes polymer transport materials with oxadiazole and triazole functional groups.
30. Onoda M: Light-emitting didoes using n-type conducting polymer: poly(p-pyridylvinylene). J Appl Phys 1995, 78:1327-1333. Describes studies on pyridine containing polymers for EL device fabrication.
31. Tian J, Wu C-C, Thompson ME, Sturm JC, Register RA, Marsella MJ, Swager TM: Electroluminescent properties of self-assembled polymer thin films. Adv Mater 1995, 7:395-398. Reports a novel procedure for device fabrication utilizing sequential dipping in polyanion and polycation solutions.
32. Faraggi EZ, Cohen G, Neumann R, Avny Y, Davidov D: Spectral tuning of electroluminescence in conjugated copolymers by application of an external electric field. Adv Mater 1996, 8:234-237. Describes variations in colour arising at different applied voltages.
33. Weaver MS, Lidzey DG, Fisher TA, Pate MA, O'Brien D, Bleyer A, Tajbakhsh A, Bradley DDC, Skolnick MS, Hill G: Recent progress in polymers for electroluminescence: microcavity devices and electron transport polymers. Thin Solid Films 1996, 273:39-47.
34. Epstein AJ, Blatchford JW, Wang YZ, Jessen SW, Gebler DD, Lin LB, Gustafson TL, Wang H-L, Park YW, Swager TM, MacDiarmid AG: Poly(p-pyridine) and poly(p-pyridinevinylene) based polymers: their photophysics and applications to scale devices. Synth Met 1996, 78:253-261. Describes symmetric contact EL devices which are well suited to AC field driving.
35. Fukuda T, Kanbara T, Yamamoto T, Ishikawa K, Takezoe H, Fukuda A: Polyquinoxaline as an excellent electron-injecting material for electroluminescent devices. Appl Phys Lett 1996, 68:2346-2348.
36. O'Brien D, Weaver MS, Lidzey DG, Bradley DDC: Poly(phenyl quinoxaline) as an electron transport material in polymer light emitting diodes. Appl Phys Lett 1996, 69:881-883. Reports large improvements in device efficiency using a quinoxaline polymer as an electron transport layer for dialkoxyphenylenevinylene emissive devices.
37. Weaver MS, Bradley DDC: Organic electroluminescence devices fabricated wih chemical vapour deposited polyazomethine films. Synth Met 1996, in press.
38. Fischer W, Stelzer F, Meghdadi F, Leising G: Self-assembled aromatic oligoazomethines on polar surfaces. Synth Met 1996, 76:201-204.
39. Kim DU, Tsutsui T, Saito S: Design and synthesis of processable electroluminescent polymer with charge transport capability. Polymer 1995, 36:2481-2483.
40. Brown AR, Pichler K, Greenham NC, Bradley DDC, Friend RH, Holmes AB: Optical spectroscopy of triplet excitons and charged excitationsw in poly(p-phenylenevinylene) light emitting diodes. Chem Phys Lett 1993, 210:61-66.
41. Greenham NC, Shinar J, Partee J, Lane PA, Amir O, Lu F, Friend RH: Optically detected magnetic resonance study of efficient two-layer conjugated polymer light-emitting diodes. Phys Rev 1996, B53:13528-13533. Presents magnetic resonance studies of bilayer EL devices and contrasts the resonance effect upon EL emission and conductivity with that for PL emission.
42. Dyakanov V, Frankevich EL, Rösler G, Schwoerer M: Excitation energy transformations in organic LED active layer. In Inorganic and Organic Electroluminescence. Edited by Mauch RH, Gumlich H-E. Berlin: Wissenschaft & Technik Verlag; 1996:129-132. Describes studies of EL, PL and photocurrent detected magnetic resonance for PPV films and devices.
43. Arkhipov VI, Bässler H, Deussen M, Göbel EO, Kersting R, Kurz H, Lemmer U, Mahrt RF: Field-induced exciton breaking in conjugated polymers. Phys Rev 1995, B52: 4932-4940.
44. Jenekhe SA: Excited-state complexes of conjugated polymers. Adv Mater 1995, 7:309-311. This paper addresses the role of intermolecular interactions in the excited state in determining emission spectra, efficiency and rate. Excimer and exciplex formation is considered and the influence of molecular structure on interactions is discussed.
45. Yan M, Rothberg LJ, Papadimitrakopoulos F, Galvin ME, Miller TM: Defect quenching of conjugated polymer luminescence. Phys Rev Lett 1994, 73:744-747.
46. Granström M, Inganäs O: White light emission from a polymer blend light emitting diode. Appl Phys Lett 1996, 68:147-149.
47. Fujii A, Yoshimoto K, Yoshida M, Ohmori Y, Yoshino K: Ultraviolet electroluminescent diode utilizing poly(methylphenylsilane). Jpn J Appl Phys 1995, 34:L1365-L1367.
48. Andersson MR, Berggren M, Ingänas O, Gustafsson G, Gustafsson-Carlberg JC, Selse D, Hjertberg T, Wennerström O: Electroluminescence from substituted poly(thiophenes): from blue to near-infrared. Macromol 1995, 28:7525-7529. Illustrates the use of steric interactions to tune the optical gap of thiophene polymers to allow access to the visible and near infrared spectral ranges (see also [46,49]).
49. Berggren M, Granström M, Inganäs O, Andersson M: Ultraviolet electrolumienscence from an organic light emitting diode. Adv Mater 1995, 7:900-903.
50. Hamaguchi M, Yohino K: Color-variable electroluminescence from multilayer polymer films. Appl Phys Lett 1996, 69:143-145. Shows how careful device design can allow two colours of emission for forward and reverse bias operation of a multilayer EL device.
51. Tasch S, Niko A, Leising G, Scherf U: Highly efficient electroluminescence of new wide band gap ladder-type poly(para-phenylenes). Appl Phys Lett 1996, 68:1090-1092. Reports highly efficient emission from a phenylene based polymer.
52. Grüner J, Friend RH, Huber J, Scherf U: A blue-luminescent ladder-type poly(para-phenylene) copolymer containing oxadiazole groups. Chem Phys Lett 1996, 251:204-210.
53. Fisher TA, Lidzey DG, Pate MA, Weaver MS, Whittaker DM, Skolnick MS, Bradley DDC: Electroluminescence from a conjugated polymer microcavity structure. Appl Phys Lett 1995, 67:1353-1357. Describes the control of emission line width and directionality within a planar optical microcavity.
54. Cimrová V, Neher D: Anomalous electrical characteristics, memory phenomena and microcavity effects in polymeric light-emitting diodes. Synth Met 1996, 76:125-128. Presents studies of the anomalous current feature seen in may devices and reports results for microcavity device structures.
55. Grüner J, Cacialli F, Friend RH: Emission enhancement in single-layer conjugated polymer microcavities. J Appl Phys 1996, 80:207-215. Reports studies of two-metal-mirror microcavity devices and analyses in detail the microcavity modification of emission.
56. Lidzey DG, Pate MA, Whittaker DM, Bradley DDC, Weaver MS, Fisher TA, Skolnick MS: Control of photoluminescence emission from a conjugated polymer using an optimised microcavity structure. Chem Phys Lett 1996, in press. The use of carefully designed cavities allows ready demonstration of enhancement and suppression of forward directed emission according to location of the emissive layer at an antinode or node in the cavity field.
57. 2 nanocrystals.
58. Holzer W, Penzkofer A, Gong S-H, Bleyer A, Bradley DDC: Laser action in poly(m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinytene). Adv Mater 1996, in press. A detailed study of the lasing properties of a conjugated polymer in solution.
59. ••].
60. Dyreklev P, Berggren M, Inganäs O, Andersson MR, Wennerström O, Hjertberg T: Polarized electroluminescence from an oriented substituted polythiophene in a light emitting diode. Adv Mater 1995, 7:43-45.
61. Cimrová V, Remmers M, Neher D, Wegner G: Polarized light emission from LEDs prepared by the Langmuir-Blodgett technique. Adv Mater 1996, 8:146-149.
62. Wu A, Kakimoto M: LEDs based on poly(p-phenylenevinylene) and polyamide LB films. Adv Mater 1995, 7:812-814. Describes fabrication of multilayer EL devices using Langmuir-Blodgett techniques.
63. Lemmer U, Vacar D, Moses D, Heeger AJ, Ohnishi T, Noguchi T: Electroluminescence from polytphenylene vinylene) in a planar metal-polymer-metal structure. Appl Phys Lett 1996, 68:3007-3009. The authors demonstrate that EL diodes can be made with in-plane electrodes and that such devices operate even when the device has an electrode spacing of 20 μm. The large electrode spacing allows ready imaging of the spatial distribution of the EL emission and confirms the imbalance in electron and hole carrier mobilities in PPV. Using stretch oriented films allows an anisotropy of eight to one to be obtained in the EL emission.
64. Lidzey DG, Pate MA, Weaver MS, Fisher TA, Bradley DDC: Photoprocessed and micropatterned conjugated polymer LEDs. Synth Met 1996, in press. Describes the influence of standard photolithographic patterning on the emissive properties of a dialoxyphenylenevinylene polymer and presents a simple method for fabrication of arrays of micron-size LEDs.
65. Westerweele E, Smith P, Heeger AJ: 'Inverted' polymer light-emitting diodes on cylindrical metal substrates. Adv Mater 1995, 7:788-790. This paper illustrates the flexibility for device fabrication afforded by conjugated polymers. A cylindrical EL device is readily constructed on a metal rod.
66. Cacialli F, Friend RH, Moratti SC, Holmes AB: Characterization of properties of polymeric light-emitting diodes over extended periods. Synth Met 1994, 67:157-160.
67. Cumpston BH, Jensen KF: Photo-oxidation of polymers used in electroluminescent devices. Synth Met 1995, 73:195-199. Describes the processes of photochemical degradation for two prototypical polymer types, namely a poly(phenylene vinylene) and a poly(thiophene).
68. 2 initial brightness.