N-type materials

Usually tills is not tire case and Table 5.2 shows values for Eg, jig and ptp for a number of semiconductors having the diamond structure. It will generally be observed from this table that the mobilities of electrons are greater than those of positive holes making these materials n-type semiconductors. 

One of the most promising uses of C60 involves its potential application, when mixed with 7r-conjligated polymers, in polymer solar cells. Most often the so-called bulk heterojunction configuration is used, in which the active layer consists of a blend of electron-donating materials, for example, p-type conjugated polymers, and an electron-accepting material (n-type), such as (6,6)-phenyl-Cgi -butyric acid methyl ester (PCBM, Scheme 9.6).38... 

In bulk semiconductor electrodes, the electric field at the solid-liquid interface causes the electrons and holes to move in opposite directions within the material. Then, depending on the type of material, n-type or p-type, the electrons or holes... 

A main recent application of perfluorinated rod-like molecules is in organic electronics where Ji-conjugated rods were functionalized with Rp-chains in order to produce electron transport materials (n-type semiconductors) with 2D conduction pathways [256] and enhanced stability against oxidation. Some examples (compounds 133-136) are collated in Fig. 35b, but their liquid crystalline phase behavior (if present) was in most cases not reported in detail [250-255]. 

The (rare-earth)-PSYCO compounds [12], Pb r (JtE) i Qa Qi Qb iq which RE is a rare-earth ion or Y, superconduct for all the common rare-earth ions (for which the material is p-type) except for RE=Ce, which naturally becomes Ce+4 in its crystal-held and then dopes the material n-type, and the material does not superconduct [13]. The same happens for Am+4 doping. Clearly, the PSYCO compounds superconduct when doped p-type, but not when doped n-type. 

The bulk electronic properties of extrinsic semiconductors are largely determined by the level of doping that is used to make the materials n-type or p-type. For non-degenerate semiconductors, the electron concentration in the conduction band and the hole concentration in the valence band are related to the Fermi energy EF and to the effective densities of states in the conduction and valence bands (Nc and Ny respectively) by... 

An undoped or pure semiconductor material is called an intrinsic semiconductor. Dopants (or impurities) are often added at very low concentration to modify the type and/or number of charge carriers in the material (i.e., adjust the Fermi level). There are two types of semiconductor materials, n-type in which the majority charge carriers are (negative) electrons, andp-fypein which the majority charge carriers are (positive) holes or electron deficiencies. Most (but not all) semiconducting metal oxides are of the n-type. 

Two semiconductor materials—n-type CdS and TiOi—have been the focus of much attention in such photocatalytic processes as the photocleavage of water and hydrogen sulphide, and the photooxidation of alcohols, carboxylates and various other organics. The majority of photoinduced processes on these materials are examined when they are in powder form. Enquiries into photocatalytic processes centre on the... 

Photodiode array detectors are an offshoot of semiconductor technology. In semiconductors, impurities have been added to pure silicon to create two classes of materials. The addition of arsenic, bismuth, phosphorous, or antimony creates a pentavalent material (n-type) that is able to function as a donor of electrons. The addition of trivalent elements such as aluminium, boron, gallium, indium, etc., to silicon gives rise to the p-lypc material, in which the trivalent material is able... 

NPN type An NPN-type of semiconductor consists of three layers of semiconductor material. N type semiconducton A semiconductor that has been doped with phosphorus to produce a material with extra electrons. 

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