Poly work function

As a function of the surface potential the electron work function for a given material depends on the state of the surface of that material (adsorption, the presence of surface compounds, etc.). For crystalline substances (see Table 3.1), various crystal faces have various electron work function values, which can be measured for single crystals. For poly crystalline substances, the final value of the electron work function depends on the contribution of the individual crystal faces to the entire area of the phase and the corresponding electron work functions the final value of the work function, however, is strongly dependent on the experimental method used for the measurement. 

Platinum electrodes are made usually from poly crystalline metal the crystal planes at the surface include both the (111) and (100) faces in approximately equal proportions. The electrochemical properties of Pt(lll) and Pt(100) faces are not identical. (Generally, the physical properties of individual metal crystal faces, such as work function, catalytic activity, etc., are different.)... 

Although the exact mechanism of the fluorenone formation is not known, it is believed that the monoalkylated fluorene moieties, present as impurities in poly(dialkylfluorenes), are the sites most sensitive to oxidation. The deprotonation of rather acidic C(9)—H protons by residue on Ni(0) catalyst, routinely used in polymerization or by metal (e.g., calcium) cathode in LED devices form a very reactive anion, which can easily react with oxygen to form peroxides (Scheme 2.26) [293], The latter are unstable species and can decompose to give the fluorenone moiety. It should also be noted that the interaction of low work-function metals with films of conjugated polymers in PLED is a more complex phenomenon and the mechanisms of the quenching of PF luminescence by a calcium cathode was studied by Stoessel et al. [300],... 

Fig. 17 Schematic representation of the device structures described in Refs. 107 and III a single-layer EHO-OPPE, b two-layer EHO-OPPE/poly-TPD, c single-layer EHO-OPPE poly-TPD blend, and d two-layer EHO-OPPE poly-TPDblend with additional spiro-Qux holeblocking layer, and their corresponding energy-level diagrams. The working functions of Ca (2.9 eV) and Cr (4.5 eV) were omitted. Reproduced with permission from [111]...

Fig. 7.145. Underpotential shift AEp, in different S(poly)/Mez+ systems as a function of the difference of electron work functions of polycrystalline S and Me, AO = Os - OMe. (Reprinted from E. Budevski, G. Staikov, and W. J. Lorenz, Electrochemical Phase Formation and Growth, p. 50, copyright 1996 John Wiley Sons. Reproduced by permission of John Wiley Sons, Ltd.)...

Since the electron work functions and the specific surface energies of different planes of the same crystal may have different values, it would be interesting to study the electronic interaction during adsorption of foreign molecules on monocrystals. Investigations of monocrystals, however, encounter many difficulties therefore, one has to restrict oneself in general to poly crystalline surfaces, which also give remarkable results because the force of interaction essentially depends on the nature of the metal and differs for the same metal from one species of adsorbed molecules to the other. 

Bias corrections determined from analysis of standards are applied to the samples under test. Use of such an average bias correction can be viewed only as an approximation to the truth so many factors contribute to bias that it is impossible to control them all. For example, as previously stated, the work function of a rhenium filament is determined by which crystal face is involved One way of loading samples on filaments is through use of single resin beads [56,57]. The beads are 100-200 xm in diameter, which is about the size of rhenium crystallites in a poly crystalline filament [17]. Clearly the work function applicable to the analysis in question may or may not be that operative when instrument calibration was carried out. Another parameter difficult to control in real-world conditions is sample purity, which also affects bias. It is impossible to purify all samples to the same degree, and contaminants adversely affect ionization efficiency low efficiency means higher filament temperatures, which in turn mean a different bias correction. These are only two of sundry variables that can affect ionization efficiency. 

Mihailetchi [134] investigated the open circuit voltage of the bulk heterojunction organic solar cells based on methanol-fullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as electron acceptor and poly[2-methoxy-5(3 ,7 -dimethyloctyloxy)-p-phenylene vinylene] (OC1C10-PPV) as an electron donor. It is known that a single layer device follows the MIM model [166] and the open circuit voltage V0c is equal to the difference in the work functions of the metal electrodes [134], If charges accumulate in the... 

Figure 106 Experimental j—U characteristics of polymer films for various temperatures (a) and two different thickness (o,A) samples at room temperature (b). (a) Steady-state currents in poly(dialkoxy-p-phenylene vinylene) (PPV) (the layer thickness d = 125 nm). After Ref. 471. (b) Response current to 10 ps rectangular voltage pulses in poly[2-5-dimethoxy-l,4-phenylene-l,2-ethenylene-2methoxy-5-(2-ethylhexyloxy)-l,4-phenylene-l,2-ethenylene (M3EH-PPV) AU = U-Ubi, where U is the applied voltage and f/bi is the built-in potential due to a difference in the work functions of the electrodes. After Ref. 472. Copyright 2000 American Institute of Physics.

Huang J. S., Miller P. F., Wilson J. S., de Mello A. J., de Mello J. C. and Bradley D. D. C. (2005), Investigation of the effects of doping and post-deposition treatments on the conductivity, morphology, and work function of poly (3,4-ethylene-dioxythiophene)/poly(styrenesulfonate) films , Adv. Funct. Mat. 15, 290-296. 

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