Mobility effect charge carriers

To reach this frequency is in no way trivial, and in particular requires a minimum mobility of charge carriers within the organic field effect transistors. This important issue will be discussed below. It has to be noted, however, that in view of the technological applications, a reliable and constant device performance may be even more important than a peak performance of the individual circuits. 

Statistical fluctuations in the mobility and charge carrier concentration of the source follower transistor s channel cause an effective charge noise A Quaker described by... 

For example, the localized electronic states within the HOMO-LUMO gap impair the performance of the field-effect transistors by increasing the field-effect threshold voltage and reducing the effective mobility of charge carriers [100]. The surface density of electronic defects in high-quality single-crystal OFETs can be less than 10 ° cm ° [38], which corresponds to interdefect distances of 0.1 jm. 

Babel, A. and Jenekhe, S.A., Field-effect mobility of charge carriers in blends of regioregular poly(3-aIkylthiophene)s, J. Phys. Chem. B 107, 1749-1754, 2003. 

LEDs built from ITO substrates with 6T which is either directly covered by Al or Mg or is prepared in a sandwich device with j8-didecyL 6T and a-bis-triiso-propylsilyl- 6T as interlayer between a6T and the metal electrode were investigated by Delannoy et al [316]. The quantum yields are summarized in Table 13.10 and show that the lower workfunction metal Mg is superior over Al as an electron-injecting electrode for the simple 6T device, whereas the structures with interlayers are independent of the contact metal. In these structures, however, it is not a6T but the silyl-compound which is the light-emitting layer. A mobility of charge carriers in 6T is estimated from time-resolved electroluminescence data to be in the range of 5 x 1cm V"" s which is much lower if compared to values obtained in field-effect or SCLC measurements (compare Section 5.1). This is discussed in terms of an emptying of traps which are hence active due to the presence of two asymmetric electrodes. 

The second insight that can be obtained from the electronic band structure is the mobility of charge carriers, which is related to the width of the conduction and valence bands. For Si the bands are rather broad, spanning more than 10 eV. This is a direct consequence of the extensive overlap of the sp orbitals on neighboring atoms. More overlap between atomic wavefunctions results in broader bands and easier transport of free charge carriers through the material. This can be quantified via the curvature of the individual bands, which is directly related to the effective mass and mobility of the charge carriers ... 

Assume that either e, the bulk dielectric constant, is known or that C has been determined from CNLS fitting of the data. In either case, b can be obtained and used in Eq. (10) to obtain from the Cr estimated value an estimate of c% the bulk concentration of the mobile positive charge carriers. Then this value of Cp may be used in Eq. (9) along with the estimated value of R to obtain an estimate of /ip, the mobility of the positive charges. Finally, the Cp estimate may be used in Eq. (11) in conjunction with the Rr estimate to calculate k% the effective reaction rate for the reacting positive charges. Thus from the four macroscopic estimates C , Cr, and Rr, one obtains estimates of the four microscopic quantities e, c% /ip, and These values and their dependences on controllable variables such as ambient temperature should then finally lead to valuable insight into the electrical behavior of the mate-rial-electrode system. 

Field-effect charge carrier mobilities in MSyT films were determined to be (3.4-6.9)xlO cm V s slightly increasing with the length of the oligoth-iophene unit from y = 8 to 12, and almost not affected by the length of the silicon atom chain. 

The semiconductor insulator interface is the primary factor that determines the field-effect mobility of charge carriers in an organic field effect transistor (OFET). Vapor phase or solution based treatments with an alkyl silane or silazine group forms a self-assembled monolayer on the surface of the insulator. Such treatments prior to the deposition of the semiconductor reduces the surface energy which improves the... 

The importance of interactions between conjugated chains is illustrated by the effect of orientation of poly(3-alkylthiophene)s on the mobility of charge carriers in field-effect transistors [12, 13]. Thin films in which the polythiophene backbone of a poly(3-alkylthiophene) is oriented perpendicular to the surface of the gate electrode (see Fig. 2) yield a higher measured hole mobility than the case in which the conjugated chains are primarily oriented parallel to the surface. This is interpreted in terms of the orientation of % stacks that define a pathway for facile charge... 

D [reaction (8)]. It is known that S dissociates rapidly to give neutral species [39, 40] according to the reaction scheme shown in Table 8.11. Although these reactions are taken into account in the simulation model, it was found by Borovkov [36] that such decomposition has no effect on the mobility of charge carriers and does not change significantly the rate of TMPD radical cation formation. 

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