Electroluminescence polyelectrolytes

Conjugated polymers like poly(l,4-phenylene-vinylene), PPV, or more generally Poly(arylene-vinylenes), PAVs have evoked considerable interest as electrically conductive and nonlinear optical materials. More recently, electroluminescence properties of PPV have attracted substantial attention, since it was first reported in 1990. Direct synthesis of PPV has been limited by its insolubility. Hence, the most commonly used routes are based on soluble polymer precursors or soluble conjugated precursors. The latter process is also commonly referred to as the sulfonium-based polyelectrolyte precursor route. PPV thin films from these solution-based routes, however, have problems related to contamination by solvents and oxidative defects in the polymer. C VP is an alternate method for the deposition of high quality thin films of PPV. Reported first by Iwatsuki et al., it was investigated for electroluminescence applications by Staring et al. ... 

Certainly one of the most interesting applications lies in the control of architecture (control of hole and electron injecting and active layers) in very thin electroluminescent devices. The existence of a precursor polyelectrolyte Pre-PPV (39,90,91) of the electroluminescent material poly(p-phenylene-vinylene) (PPV) (92) makes it possible to fabricate polyion multilayer film architectures, in which the Pre-PPV can subsequently be converted to PPV by thermal annealing (19,34-38,87,88,93). The first electroluminescent devices have been prepared and it was found that devices as thin as 13 nm emit light (88). Tum-on voltages of less than 2 V are required to generate light (35) and even an influence of the film architecture on the luminescent properties has been observed (88). However, the structural details of these films are presently not understood and it is not clear how device properties are influenced by film composition and architecture. We have recently shown that the thermal conversion of Pre-PPV to PPV can be carried out with preservation of a layered structure. These results were obtained by neutron reflectometry on... 

Water-soluble PPEs 41 (Scheme 6.20) were investigated for appHcations in electroluminescent devices by Thiinemann [76,77]. The structure and processability of this polyelectrolyte were manipulated by complexation with long-chain alkylammonium cations. 

Huang, R, L.T. Hou, H.L. Shen, J.X. Jiang, F. Wang, H.Y. Zhen, and Y. Cao. 2005. Synthesis, photophysics, and electroluminescence of high-efficiency saturated red light-emitting polyfluorene-based polyelectrolytes and their neutral precursors. J Mater Chem 15 (25) 2499-2507. 

Devices based on composites of nanocrystals with polymers or polyelectrolytes have been fabricated to exploit electroluminescent and related properties of nanocrystalline media. These devices utilize thin films of composites obtained by layer-by-layer deposition using self-assembly, drop-casting, or spin-casting methods. 

The chemical structures of a number of mainchain, highly conjugated polymers used in OLEDs are shown in Fig. 7.6. The electroluminescence of the polymer poly(l,4-phenylenevinylene) (PPV) was reported in 1990 [10], Since PPV itself is completely insoluble and thin films are only accessible by thermal conversion of a soluble polyelectrolyte precursor, a number of soluble PPV-derivatives have been developed. Among these are MeH-PPV [20] and a number of soluble PPVs... 

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