Poly charge-carrier generation

Fig. 23 (a) Dependence of the hole mobility in a film of poly-spiro-bifluorene-co-benzothiazole (PSF-BT) as function of the time elapsed after charge carrier generation by a 130 fs laser pulse at different applied voltages. The horizontal lines represent the electron and hole mobilities inferred from ToF experiments, (b) Momentary mobility as a function of the averaged distance that a carrier travelled after a given time. The inset depicts the chemical structure of PSF-BT. From [154] with permission. Copyright (2009) by the American Institute of Physics... 

The photoconductivity of poly[2-(N-carbazolyl)ethyl vinylether]91,92) and particularly of poly(N-acryloylcarbazole)91) is much inferior to that of PVK. In the case of the acrylic polymer the reported photocurrents are at least two orders of magnitude lower. The poor charge carrier generating efficiency is blamed for low photocurrents91 The relatively poor performance of the vinylether polymer is how ever attributed to charge carrier mobility92). 

Fig. 9.26 Temporal characteristics of photo-induced absorptions associated with charge carriers generated by short laser pulses, (a) IR absorption in MEH-PPV (reprinted from Moses et ah, 2001 copyright 2001, with permission from Elsevier) and (b) optical absorption in a poly(indenofluor-ene) (reprinted from Silva et ah, 2001 copyright 2001, with permission from Elsevier). See text for details.

Fig. 2.3 Quantum yield for charge carrier generation as a function of the electric field strength determined at 295 K for three poly-silylenes poly(biphenyl methyl silylene),...

Crystals of poly[2,4-hexadiyne-l,6-diol bis(p-toluenesulphonate)] [59, 60] are highly photoconductive, with high carrier mobilities, near 20m V s even at low electric fields. This corresponds to drift velocities of about 2.2 x 10 m s i.e. close to the velocity of sound in the material. It is interesting to note that the spectral dependence of photoconductivity (the so called action spectrum) in this and other polyacetylenes does not follow the absorption spectrum, but is shifted towards shorter wavelengths. Charge-carrier generation follows the Onsager one-dimensional model, at least for electric fields up to 10 V m [60, 61]. 

Binh, N. T., Gailberger, M., and Bassler, H., Photo-conduction in poly(3-alkylthiophene) I. Charge carrier generation, Synth. Met., 47, 77, 1992. 

Charge carrier generation and transport in poly(3-dodecylthiophene) have been recently studied in detail [446,447], The mechanism of photocarrier generation... 

Poly(phenylmethylsilane) (PMPS) was investigated by Kepler et al. (1983, 1984, 1987). Figure 32 shows the wavelength dependence of the absorption and the normalized photocurrent. The spectral dependence of the photocurrent indicates that carrier generation occurs by an extrinsic process which results primarily from an interaction of charge-transfer excitons with the surface. The argument is similar to that proposed earlier by Kepler (1976) to describe hole... 

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