PEDOT,

Figure 15-24. Spectral response or devices nude wilh different PEOPT polymer thicknesses Al/C ) (35 nm)/PEOPT (30 nin)/PEDOT-PSS (110 unU/lTO (120 ninj/glass (solid circles) and AI/Cm (35 nm)/PEOPT (40 iini)/Pl DOT-PS.S (110 mn)/lTO (120 ninj/glass (open circles). The absorption spectrum of the PEOPT polymer is plollcd for comparison (solid line) (reproduced by permission of Wiley-VCH from Ref. (92]).

A thin layer deposited between the electrode and the charge transport material can be used to modify the injection process. Some of these arc (relatively poor) conductors and should be viewed as electrode materials in their own right, for example the polymers polyaniline (PAni) [81-83] and polyethylenedioxythiophene (PEDT or PEDOT) [83, 841 heavily doped with anions to be intrinsically conducting. They have work functions of approximately 5.0 cV [75] and therefore are used as anode materials, typically on top of 1TO, which is present to provide lateral conductivity. Thin layers of transition metal oxide on ITO have also been shown [74J to have better injection properties than ITO itself. Again these materials (oxides of ruthenium, molybdenum or vanadium) have high work functions, but because of their low conductivity cannot be used alone as the electrode. 

Figure 15-23. Calculalcil value ol ihc square of (lie normalized electrical field i 2 at the Cw/PEOPT interface lor PEOPT thickness of 30 nm (solid line) and 40 nm (dashed line) versus thickness of the CM layer at a wavelength of 460 nin. The inset shows the calculated distribution of the square of Ihc normalized opiical field E ] inside an 1TO (120 mn)/PEDOT-PSS (110 iini)/PEOPT(30 nm)/CW) (32 nm) device at the same wavelength (reproduced by permission of Wilcy-VCH from Ref. 92 ).

Electronically conducting polymers (ECPs) such as polyaniline (PANI), polypyrrole (PPy) and po 1 y(3.4-cthy 1 cncdi oxyth iophcnc) (PEDOT) have been applied in supercapacitors, due to their excellent electrochemical properties and lower cost than other ECPs. We demonstrated that multi-walled carbon nanotubes (CNTs) prepared by catalytic decomposition of acetylene in a solid solution are very effective conductivity additives in composite materials based on ECPs. In this paper, we show that a successful application of ECPs in supercapacitor technologies could be possible only in an asymmetric configuration, i.e. with electrodes of different nature. 

M. Vazquez, J. Bobacka, M. Luostarinen, K. Rissanen, A. Lewenstam, and A. Ivaska, Potentiometric sensors based on poly(3,4-ethylenedioxythiophene) (PEDOT) doped with sulfonated calix[4]arene and calix[4]resorcarenes. J. Solid State Electrochem. 9, 312-319 (2005). 

PEDOT PSS Poly(3,4-ethylenedioxythiophene) poly(4-styrenesulphonic acid) PPV Poly[(m-phenylenevinylene)-c >-(2,5-dioctoxy-p-... 

LAJs incorporating polymer films on top of the organic SAMs showed that these junctions allow for studying the correlation between electrical properties and chemical structure. Both de Boer et al. [80] (Fig. 7) and Rampi et al. [79], by spin-coating respectively PEDOT PSS and PPV on top of alkane SAMs, extracted from the electrical measurement [i = 0.57 A-1 and [j = 0.90 A-1. Rampi et al. also showed that it is possible to measure electrical properties of polyphenyl chains with a [1 0.61 A, and that the PPV polymer layer is much more conductive that... 

Fig. 12 In situ optical switching of the current flowing through a DAE monolayer assembled in a PEDOT PSS interlayer-based LAJ. (a) Comparison of the current densities flowing through as assembled open and closed isomer and upon in-situ photoisomerization.

FIGURE 1.4 Optical transmission spectra of (a) PEDOT-PSS and (b) PANI-CSA. 

EL from tetraalkoxy-substituted PPV 20, synthesized by Gilch polymerization, was recently reported [84], A multilayer device ITO/PEDOT/20/PBD/LiF/Al with PBD as an ETL emits green-yellow light with a luminescent efficiency of 0.121m/W, a maximum brightness of 8200 cd/m2, and a turn-on voltage of 5 V. 

The same group recently reported that the TBB defects can be brought below the nuclear magnetic resonance (NMR) detection limit by employing similar polymerization conditions (i-BuOK in THF at room temperature) in the synthesis of naphthyl-substituted PPVs 51-53 [112]. Although the absorption and PL spectra of all three polymers are similar, the EL can be finely tuned between 486 nm (for 52) and 542 nm (for 53). The external QE (studied for ITO/PEDOT/polymer/Ba/Al device) is also sensitive to the substituents pattern in the naphthyl pendant group 0.08% for 51, 0.02% for 52, and 0.54% for 53. 

SCHEME 2.15 Dependence of the electroluminescence of alkoxyphenyl-PPV copolymers on the comonomers ratio (PLED configuration ITO/PEDOT or PANI/polymer/Ca or Yb/Ag). 

Likewise, copolymers 90 have higher EL efficiency than homopolymers DHF-PPV 57 or MEH-PPV 13, due to more balanced charge injection and transport properties. Copolymer 90 with 7.5 wt% loading of dialkoxyphenylene comonomer gave the highest QE. The device with an ITO/PEDOT/90/Ca configuration showed remarkably higher efficiency (2.4cd/A) than devices fabricated with other copolymers in the series (0.65-1.0cd/A) [141],... 

The diphenylamino-substituted PPV107, with solubilizing alkoxy groups, was synthesized by Shi and Zheng [150] via Wittig-Horner reaction (Chart 2.23). Its PL (555 nm) is very similar to that of diamino-PPV 64 and dialkoxy-PPV 14 homopolymers. The PLQY is rather high in solution (80%), but it drops to only 8% in films. Consequently, only a moderate EL efficiency of 0.6cd/A was obtained with this material (device ITO/PEDOT/107/Mg/Al) [150]. Almost simultaneously, Kido and coworkers [151] reported a similar diphenylamino-substituted PPV copolymer 108, which affords very efficient PLEDs. The device ITO/PEDOT/108/Ca/Al... 

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