Conjugated and electroluminescent polymers

Current Opinion in Colloid and Interface Science

Volumn 4, Issue 2, 1999, Pages 159-164

  Cacialli, Franco ^a  

^a UNIVERSITY OF CAMBRIDGE   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

POLYMER;

CHEMICAL STRUCTURE; CONJUGATION; LUMINESCENCE; PHOSPHORESCENCE; REVIEW; SEMICONDUCTOR;

EID: 0032809541     PISSN: 13590294     EISSN: None     Source Type: Journal    
DOI: 10.1016/S1359-0294(99)00020-5     Document Type: Article

References (46)

1. Baldo MA, Obrien DF, You Y, Shoustikov A, Sibley S, Thompson ME, Forrest SR: Highly efficient phosphorescent emission from organic electroluminescent devices. Nature 1998, 395:151. This is an outstanding paper, showing a clever approach to high efficiency LEDs via access to triplets photophysics, it is simple, since it uses 'trivial' doping of a phosphorescent dye into an electroactive host, yet very ingenious, in the choice of the dye and of the device structure. It also gives a number of hints and suggestions, for future experiments, aimed at further optimisation of the devices and at a better understanding of the properties of triplets in organic semiconductors.
2. Cleave V, Yahioglu G, Le Barny P, Friend RH, Tessler N: Harvesting singlet and triplet energy in polymer LEDs. Adv Mat 1998, in press. Another excellent paper are made on the triplets photophysics, which confirms the results of [1], but by making use of a polymeric host. Further suggestions on how to use LEDs and polymer/dyes blends to probe triplet energies.
3. 2 solar cells with high photon-to-electron conversion efficiencies. Nature 1998, 395:583. An elegant demonstration of how solid thin films of organic semiconductors can provide high-quality, flexible and technologically robust contributions to a variety of applications requiring charge transport. In this case a spiro-linked phenyl-amine based molecule substitutes a liquid electrolyte, improving processibility and device performance.
4. Granström M, Petritsch K, Arias AC, Lux A, Andersson MR, Friend RH: Laminated fabrication of polymeric photovoltaic diodes. Nature 1998, 395:257. This paper describes a method to extend control over the morphology of polymer mixtures without losing the benefits of a diffuse junction between heterogeneous polymers, and at the same time taking advantage of the peculiarity of the materials, such as the tendency of 2 polymer films to interpenetrate when they are pressed together at moderately high temperature. The paper highlights a theme, namely that of the importance of the control of morphology in view of electro-optical properties, which is likely to become dominant in the near future.
5. Chua BS, Cacialli F, Davies JE, Feeder N, Friend RH, Holmes AB, Marseglia EA, Moratti SC, Brédas J-L, dos Santos DA: New luminescent PPV derivatives for LED applications. Mat Res Soc Symp Proc: Symposium J 1998, 488:87.
6. Feast WJ, Cacialli F, Daik R, Friend RH, Herzog E, Heywood BR, Hobson L, Megson JL, Snowden D: Precision and control in polymer synthesis macromolecular symposia (Macromolecular Chemistry and Physics) in press.
7. Feast WJ, Cacialli F, Daik R, Friend RH: Synthesis and properties of poly(arylene vinylene)s with well defined structures ACS. Polymer Preprints 1998, 39:712.
8. Redecker N, Bradley DDC, Inbasekaran M, Woo EP: Nondispersive hole transport in an electroluminescent polyfluorene. Appl Phys Lett 1998, 73:1565. A thorough report of a classical experiment (time-of-flight) on a relatively new material, which highlights the polymer high quality, in terms of purity and low energetic and positional disorder.
9. Janietz S, Bradley DDC, Grell M, Giebeler C, Inbasekaran M, Woo EP: Electrochemical determination of the ionization potential and electron affinity of poly(9,9-dioctylfluorene). Appl Phys Lett 1998, 73:2453. Complementary to reference [8], this paper is a careful description of the often overlooked problems in the interpretation of electrochemical data (and in particular cyclic voltammetry) of conjugated polymers. The results are very valuable to the organic semiconductor community.
10. Issaris A, Vanderzande D, Adriaensens P, Gelan J: Polymerization mechanism of 1-[(butylsulfi(o)nyl)methyl]-4- (halomethyl)benzene: the effect of polariser and leaving group. Macromolecules 1998, 31:4426. This paper presents a very versatile synthesis route to poly(phenylenevinylene) (PPV) from a precursor polymer that is amenable to the conventional nonaqueous processing techniques. The technique allows discrimination of some of the factors affecting the polymerisation products.
11. Hoofman RJOM, dehaas MP, Siebbeles LDA, Warman JM: Highly mobile electrons and holes on isolated chains of the semiconducting polymer poly(phenylenevinylene). Nature 1998, 392:54. This paper is a fine example of how an old technique (microwave conductivity) can be applied to new problems and materials and yield detailed microscopic information, otherwise exceptionally difficult to obtain. The results are unexpected and call for a large and systematic screening of the charge mobilities in several groups of materials.
12. 2 in PPV based LEDs, under pulsed operation. The main conclusion of this outstanding paper is that Laser action is currently limited by device efficiency, rather than peak current density. The paper also reports on an ingenious optical, non-invasive measurement of carrier densities under operation.
13. Köhler A, dossantos DA, Beljonne D, Shuai Z, Bredas JL, Holmes AB, Kraus A, Mullen K, Friend RH: Charge separation in localised and delocalised electronic states in polymeric semiconductors. Nature 1998, 392:903. This paper provides a deep insight into the nature of electronic states by means of a careful re-elaboration of an apparently trivial experiment: the measurement of the photocurrent in PPV at high photon energies. The study identifies the presence of localised and delocalised orbitals, the bearing of which device physics are still to be completely analysed and understood. It may possible that the very high charge mobilities reported in [11] and [12], involve transport through these delocalised states.
14. Vacar D, Dogariu A, Heeger AJ: Interaction range for photoexcitations in luminescent conjugated polymers. Adv Mater 1998, 10:669.
15. Alvarado SF, Seidler PF, Lidzey DG, Bradley DDC: Direct determination of the exciton binding energy of conjugated polymers using a scanning tunnelling microscope. Phys Rev Lett 1998, 81:1082. The high sensitivity of the STM is used in order to determine the position of electron affinity and ionisation potential in a PPV derivative and in a polyfluorene. The experiment is carried out by measuring the height of the STM tip over a polymer/Au substrate, as a function of the tip/Au potential, at constant tunnelling current and determines the onset of charge injection into the material by a step-like increase of the tip height over the substrate. It is an original method which opens the way to a systematic characterisation of the electronic structure of conjugated polymers.
16. Liess M, Jeglinski S, Vardeny ZV, Ozaki M, Yoshino K, Ding Y, Barton T: Electroabsorption spectroscopy of luminescent and nonluminescent pi-conjugated polymers. Phys Rev B - Cond Matt 1997, 56:15712. This is an interesting, detailed study of the electroabsorption response in luminescent and non-luminescent conjugated polymers with a significant effort to provide information on the nature of the exciton states (both of Bu and Ag symmetry), also with the help of Sum Over States (SOS) calculations, applied to a model which takes into account the vibrational properties and the inhomogeneity of the studied polymers.
17. Schweitzer B, Wegmann G, Giessen H, Hertel D, Bassler H, Mahrt RF, Scherf U, Mullen K: The optical gain mechanism in solid conjugated polymers. Appl Phys Lett 1998, 72:2933.
18. Mcgehee MD, Gupta R, Veenstra S, Miller EK, Diazgarcia MA, Heeger AJ: Amplified spontaneous emission from photopumped films of a conjugated polymer. Phys Rev B - Cond Matt 1998, 58:7035.
19. Frolov SV, Vardeny ZV, Yoshino K: Cooperative and stimulated emission in poly(p-phenylene-vinylene) thin films and solutions. Phys Rev B - Cond Matt 1998, 57:9141.
20. Graupner W, Cerullo G, Lanzani G, Nisoli M, List EJW, Leising G, De Silvestri S: Direct observation of ultrafast field-induced charge-generation in ladder-type poly(para-phenylene). Phys Rev Lett 1998, 81:3259-3263. Charge photogeneration upon application of an electric field is investigated in Me-LPPP LEDs, by monitoring the spectral signatures of the charged species with femtosecond pump-probe spectroscopy. It is a neat experiment which identifies polaron generation from exciton fission without intermediate states.
21. deMello JC, Tessler N, Graham SC, Friend RH: Ionic space-charge effects in polymer light-emitting diodes. Phys Rev B - Cond Matt 1998, 57:12951.
22. Manzanares JA, Reiss H, Heeger AJ: Polymer light-emitting electrochemical cells: a theoretical study of junction formation under steady-state conditions. J Phys Chem B 1998, 102:4327.
23. Blom PWM, Vissemberg MCJM: Dispersive hole-transport in poly(p-phenylene vinylene). Phys Rev Lett 1998, 80:3819.
24. Granlund T, Theander M, Berggren M, Andersson M, Ruzeckas A, Sundstrom V, Bjork G, Granstrom M, Inganas O: A polythiophene microcavity laser. Chem Phys Lett 1998, 288:879. This is another paper showing how the lamination technique may become of outstanding interest for semiconductor polymer electronics. In this case lamination is used in order to fabricate organic microcavity structures with 2 dielectric mirrors. The advantage is in the mild processing conditions required by the technology, and hence in the reduced damage to the active material.
25. Dodabalapur A, Berggren M, Slusher RE, Bao Z, Timko A, Schiortino P, Laskowski E, Katz HE, Nalamasu O: Resonators and materials for organic lasers based on energy transfer. IEEE J Selected Topics Quantum Electr 1998, 4:67. This is an account on the use of energy transfer for the fabrication of optically pumped lasers with organic/polymeric materials capable of charge transport. The active materials are doped films with small molecule hosts and dye, oligomer, and conjugated polymer emitters. The authors also demonstrate a number of novel patterning and fabrication procedures developed specifically for organic-based lasers.
26. Rogers JA, Meier M, Dodabalapur A: Using printing and molding techniques to produce distributed feedback and Bragg reflector resonators for plastic lasers. Appl Phys Lett 1998, 73:1766.
27. Berggren M, Dodabalapur A, Slusher RE, Bao Z, Timko A, Nalamasu O: Organic lasers based on lithographically defined photonic-bandgap resonators. Electron Lett 1998, 34:90.
28. Berggren M, Dodabalapur A, Slusher RE, Bao Z: Organic lasers based on Förster transfer. Synth Met 1997, 91:65.
29. Berggren M, Dodabalapur A, Slusher RE, Timko A, Nalamasu O: Organic solid-state lasers with imprinted gratings on plastic substrates. Appl Phys Lett 1998, 72:410.
30. Frolov SV, Vardeny ZV, Yoshino K: Plastic microring lasers on fibers and wires. Appl Phys Lett 1998, 72:1802.
31. Frolov SV, Fujii A, Chinn D, Hirohata M, Hidayat R, Taraguchi M, Masuda T, Yoshino K, Vardeny ZV: Microlasers and micro-LEDs from disubstituted polyacetylene. Adv Mater 1998, 10:869.
32. Lidzey DG, Bradley DDC, Skolnick MS, Virgili T, Walker S, Whittaker DM: Strong exciton-photon coupling in an organic semiconductor microcavity. Nature 1998, 395:53. This is an interesting report of how the peculiar physics of organics may allow exploration of the solid state properties beyond the range observable with inorganic structures. An outstanding example of conjugated polymer physics, with many hints to possible further developments.
33. Becker H, Friend RH, Wilkinson TD: Light emission from wavelength-tunable microcavities. Appl Phys Lett 1998, 72:1266. This paper is a concise yet complete report of the fabrication of organic microcavity structures whose emission is tunable on a very broad range (56 nm), thanks to the incorporation of a liquid crystal layer in the device structure.
34. Dodabalapur A, Bao Z, Makhija A, Laquindanum JG, Raju VR, Feng Y, Katz HE, Rogers J: Organic smart pixels. Appl Phys Lett 1998, 73:142.
35. Sirringhaus H, Tessler N, Friend RH: Integrated optoelectronic devices based on conjugated polymers. Science 1998, 280:1741.
36. Bharathan J, Yang Y: Polymer electroluminescent devices processed by inkjet printing: i. polymer light-emitting logo. Appl Phys Lett 1998, 72:2660.
37. Pede D, Serra G, Derossi D: Microfabrication of conducting polymer devices by ink-jet stereolithography. Mater Sci Eng C - Biomimet Mater Sens Syst 1998, 5:289.
38. Hebner TR, Wu CC, Marcy D, Lu MH, Sturm JC: Ink-jet printing of doped polymers for organic light emitting devices. Appl Phys Lett 1998, 72:519.
39. Chang SC, Bharathan J, Yang Y, Helgeson R, Wudl F, Ramey MB, Reynolds JR: Dual-color polymer light-emitting pixels processed by hybrid inkjet printing. Appl Phys Lett 1998, 73:2561.
40. Andersson A, Johansson N, Bröms P, Yu N, Lupo D, Salaneck WR: Fluorine tin oxide as an alternative to indium tin oxide in polymer LEDs. Adv Mater 1998, 10:859.
41. Ho PKH, Granstrom M, Friend RH, Greenham NC: Ultrathin self-assembled layers at the ITO interface to control charge injection and electroluminescence efficiency in polymer light-emitting diodes. Adv Mater 1998, 10:769.
42. Osada T, Kugler T, Bröms P, Salaneck WR: Polymer-based light-emitting devices: investigations on the role of the indium-tin oxide (ITO) electrode. Synth Met 1998, 96:77.
43. Parente V, Pourtois G, Lazzaroni R, Bredas JL, Ruani G, Murgia M, Zamboni R: The vibrational signature of the aluminium/polythiophene interface. Adv Mater 1998, 10:319.
44. Parthasarathy G, Burrows PE, Khalfin V, Kozlov VG, Forrest SR: A metal-free cathode for organic semiconductor devices. Appl Phys Lett 1998, 72:2138. A good report on the progresses in cathode engineering for organic LEDs which uses a conjugated molecule in conjunction with sputtered indium-tin oxide in order to increase the cathode transparency and the electron-injection efficiency. Interestingly it is argued that sputtering induced damage plays a beneficial role in determining the injection properties.
45. Glebeler C, Antoniadis H, Bradley DDC, Shirota Y: Space-charge-limited charge injection from indium tin oxide into a starburst amine and its implications for organic light-emitting diodes. Appl Phys Lett 1998, 72:2448.
46. Kim JS, Granström M, Friend RH, Johansson N, Salaneck WJ, Daik R, Feast WJ, Cacialli F: Indium-tin oxide treatments for single and double-layer polymeric light-emitting diodes: The relation between the anode physical, chemical and morphological properties and the device performance. J Appl Phys, 1998, 84:6859.