Pentacene electric field

Fig. 17 Temperature dependence of the hole mobility measured in an FET with (a) pentacene and (b) P3HT as active layers. Parameter Is the gate voltage. Data fitting using the Fishchuk et al. theory in [102] yields values for the mobility and the disorder potential extrapolated to zero electric field and zero carrier concentration. To is the Meyer-Nedel temperature (see text). From [102] with permission. Copyright (2010) by the American Institute of Physics...

Minari T, Nemoto T, Isoda S (2006) Temperature and electric-field dependence of the mobility of a single-grain pentacene field-effect transistor. J Appl Phys 99 034506... 

Mottaghi and Horowitz [164] have investigated the degradation of carrier mobility in pentacene TFTs due to effect of electric field. They fabricated pentacene-based OTFTs with bottom-gate, top-contact architecture. Alumina was used as substrate. In one set of devices pentacene was deposited directly on alumina. In the second set of devices a fatty... 

Figure 178 The EL QE and overall recombination probability (PR) (a), and the recombination zone width (b) vs. electric field applied to the EL devices ITO/TPD/% DPP Alq3/Alq3/Mg Ag with different mol% concentration of 6,13-diphenlyl pentacene (DPP) in Alq3 as emitter. After Ref. 68. Copyright 2001 American Institute of Physics, with permission.

Fig. 2.2. (A) Illustration of the source of statistical fine structure (SFS) using simulated absorption spectra with different total numbers of absorbers N, where a Gaussian random variable provides center frequencies for the inhomogeneous distribution. Traces (a) through (d) correspond to N values of 10, 100, 1,000, and 10,000, respectively, and the traces have been divided by the factors shown. For clarity, yjj = Fi/10. Inset several guest impurity molecules are sketched as rectangles with different local environments produced by strains, local electric fields, and other imperfections in the host matrix. (B) SFS detected by FM spectroscopy for pentacene in p-terphenyl at 1.4K, with a spectral hole at zero relative frequency for one of the two scans. Note the repeatable fine structure...

Fig. 2.8. Left (A) Optical configuration for exciting a single molecule with a nearfield fight source, an Al-coated pulled optical fiber. Application of a potential V to the A1 coating produces a highly anisotropic DC local electric field. (B) Spectra of pentacene in p-terphenyl molecules at various applied potentials, (a-b) saturation method to identify molecules close to the tip, (c-1) transverse dithering with Stark shift. For details, see [63]...

Figure 20.4 (a) Results of a two-dimensional simulation of a pentacene OFET with geometric parameters close to the bottom-contacted device investigated with potentiometry, for // = 0.014 cm V s and an effective injection barrier of 0.42 eV, and (b) construction of an injection barrier of 0.73 eV out of the effective barrier of 0.42 eV and the electric field close to the source contact, as obtained in the simulation for a gate voltage of Uq = -30 V. 

Figure 20.9 (a) Comparison of electric field distribution with (sobd bnes) and without (dashed) OTS treatment of the gate oxide, (b) AFM picture of a pentacene OFET with untreated gate oxide, revealing a channel length of about 17 pm. 

Abstract. Pentacene organic field effect transistors (OFETs) electrical and structural properties have already been analysed from the point of view of different gate dielectric and growth conditions utilization. The AFM and micro Raman investigations show that the first organic monolayer at the pentacene/dielectric interface are essential determinants of carrier transport phenomena and achievable drain current of pentacene OFETs. 

Table 1. Spin-coated CPB thin film (<20 nm) deposition condition and pentacene-based TFT device performance (mobility and on/off ratio) - polymer/crosslinker concentration ratio (mg/ml mg/ml), solvent, film thickness (D, nm), RMS roughness (p, nm), leakage current density at an electric field of 2 MV/cm (J, A/cm2), mobility (ji, cm2/Vs), and Current On/off Ratio (/<, /< ) ...

FIGURE 1.1.8 Evolution of the hole mobility as a function of the magnitude of the electric field in a one-dimensional array of pentacene molecules separated by 4 A. 

We determine the molecular orientation of pentacene by comparing the angular variation of peaks in Figure 4.2.5(a) with their respective orbital orientations in Figure 4.2.6. The 7T -orbital resonance is most intense near normal incidence, where the electric field vector is in the substrate plane. Thus, the 7T -orbital is preferentially oriented in the substrate plane, and pentacene is oriented edge-on in the thin film. The 7T -variation indicates only the conjugated plane tilt we cannot determine the long-axis tilt from this resonance. 

In two different investigations of single pentacene molecules in -terphenyl [10, 36] it was found that calculated values for 1 were all much smaller than the experimental values. In these calculations, however, the triplet state was treated as a single level. By using the correct expression (Eq. 8) and approximate corrections for the local field, the saturation intensities of [36] were recalculated by the authors of this chapter and much better agreement between experiment and theory than in [36] was found. The experimental values of Is did still show quite a large scatter which did not follow the variations in the ISC parameters 23 and which were found to be different up to a factor of three from molecule to molecule [36] (see also 1.2.4.3). Therefore, this distribution of saturation intensities may arise due to differences in local fields and variations in the orientation of the molecular transition dipole moments with respect to the electric field of the exciting laser. 

Pentacene in p-terphenyl was the first system where single molecules were detected by optical excitation spectroscopy and was also the first system in which the effect of external electric fields on single molecules [20] was studied. 

Figure 15. Stark shift of individual pentacene molecules [20]. The molecular resonances are shifted towards smaller frequencies, independent from the sign of the electrical field (U = 0.87kV). The magnitude of the frequency shift varies from molecule to molecule and depends for molecule C additionally on the sign of the electrical field.

Figure 16. Experimental (circles) and fitted (lines) Stark shifts of four individual pentacene molecules as a function of the applied electrical field [20]. Clearly a quadratic dependence of varying magnitude dominates. In case of molecule C an additional linear term results in an asymmetric behavior and a shifted Stark parabola.

In a similar manner to how the quadrupole of pentacene can induce changes in the HOMO and LUMO levels at the organic/organic interface, other molecular multipole moments can create a static electric field at the interface. A recent study... 

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