Charge transport materials

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. 

The prototype DSCs used liquid electrolytes, typically L/I2 in an organic solvent such as propylene carbonate. The electron generation/collection problem in this cell has been discussed analytically with the help of intensity-modulated photocurrent and photovoltage spectroscopy [314]. A particularly challenging issue has been the replacement of the liquid electrolyte with a solid charge-transport material... 

Mobility data on bipolar charge-transport materials are still rare. Some bipolar molecules with balanced mobilities have been developed [267], but the mobilities are low (10 6—10 8 cm2/Vs). Up to now, no low molecular material is known that exhibits both high electron and hole conductivity in the amorphous state, but it is believed that it will be only a matter of time. One alternative approach, however, is to use blends of hole and electron transporting materials [268]. 

Most of the materials used as charge transport materials (CTMs) in commercial photoconductors work by a positive hole-transport mechanism, as indicated in Figure 4.10. Hole transport p-type semi-conductors are materials that are electron rich and give up their electrons readily. Because of this property they are easily oxidised by air and hght, and a balance must be obtained between environmental... 

Figure 4.13 Charge transport materials for dual layer photoconductors.

Pol y(th iophene-co-selenophcnc) derivatives, (IV), were previously prepared by the authors (6) and used as semiconductors or charge-transport materials. 

As charge transport materials, the polysilanes are unique in that the active sites are on the polymer backbone itself. In other electrophotographic materials, charged sites... 

We have a specific interest in the self-assembled structures formed by poly(ferrocenylsilane) block copolymers, such as poly(ferrocenyldimethylsilane-Z -dimethyl-siloxane) (PFS-PDMS) and (ferrocenyldimethylsilane-Z>-isoprene) (PFS-PI). The PFS block contains an iron atom in the main chain repeat unit. These polymers are particularly promising for novel applications, since they can be used as charge-transport materials and, by pyrolysis, as precursors to ferromagnetic ceramics [4-6], Moreover, they can by synthesized with a very narrow molar mass distribution, with excellent control over chain length and composition [7], An important feature of PFS is that the polymers bearing two methyl groups on the silane unit are crystalline, whereas polymers with two different substituents on each silane (methyl, ethyl methyl, phenyl) are atactic and remain amorphous. This feature of the polymer composition has a strong influence on the type of self assembled structures that these poly-... 

For efficient hole transport the materials should be constructed such as to prevent dimer formation in both the ground and excited states. Excimer forming sites, in fact, may constitute traps for charge transport materials [45-47]. More recently, it has been shown that the host polymer can also affect the transport properties of the film [48]. 

The spiro compound 61 has been prepared and evaluated as a new charge transport material <07AM4049>. It has also been demonstrated that several 3-boryl-2,2 -bithiophene systems, for instance 62, may have potential as full-color emissive materials <07AG(E)4273>. The donor-acceptor system 5-diphenylamino-5 -... 

Title Acrylic Polymer and Charge Transport Material... 

Isotactic and syndiotactic poly(9-fluorenyl methacrylate)s have been prepared that are effective as hole mobility charge transport materials and as electrical conductors of charge transport materials. 

Measurement of Hole Mobility of Charge Transport Material (TOP Method)... 

Title Polyester Having Jt-Conjugated Group in Side Chain and Charge Transporting Material Using the Same... 

Beginning with 9-fluorene carboxylic acid, high molecular weight poly(9-hydroxy methyl-9-fluorene carboxylic acid) has been prepared by the homopolymerization of 9-hydroxymethyl-9-fluorene carboxylic acid using trifluoro methanesulfonate as the catalyst. This polymeric agent readily formed donor-acceptor complexes with 1,3-dinitrobenzene and is suitable as a charge transport material. 

Polymers having a central core consisting of [2,3-b]-thienothiophene were prepared having a M > 6000 daltons and M > 9000 daltons and used as semiconductors or charge transport materials in electronic devices. By varying the aromatic or ahphatic content of this material, a X ax between 380 and 462 nm was obtained. 

Copolymers of 9-H,H-fluorene and thiophene, (1), were prepared by the author [2] and used as charge transport materials in electronic devices. 

Poly(3,3 -dialkyl-2,2 5 2-terthiophene) derivatives, (11), prepared by McCulloch [3] were also effective in electronic components as charge transport materials and semiconducters. 

Polymers and elastomers comprising at least one 9-H,H-fluorene group and at least one arylene group have been prepared. These materials are suitable for use as semiconductors or charge transport materials in optical, electrooptical, or electronic devices, including field-effect transistors, electroluminescent, photovoltaic, and sensor devices. 

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