Compound semiconductors hole mobility

Compound 53 is also a very stable organic semiconductor with a high hole mobility of 0.31 cm. ... 

Table tr.1-20 Electron mobilities /Xn and hole mobilities /Xp of Group IV semiconductors and IV-IV compounds... 

In this chapter, we will be dealing mainly with sensitization of n-type semiconductor electrodes where oxidation of the dye takes place through transfer of an electron from the photoexcited dye to the conduction band of the semiconductor. The semiconductor is used as an anode and the charge transfer process monitored as anodic photocurrent. Though not discussed here, reduction of photoexcited dyes is also known to occur through a valence band mechanism. This can only be observed in compounds with a high hole mobility such as SiC or GaP. 

In conclusion it must be stressed that, for applications of the semiconductor properties of organic dyes and other compounds, the important factors besides the energy gap AE and the primary quantum efficiency r of the generation of electron-hole pairs are the characteristic parameters mobility and lifetime of electrons and holes. 

Among arylamine semiconductors, indolo[3,2-ib]carbazole (5) is an appealing system for studies because it has a relatively large and planar molecular structure to enable facile establishment of higher structural order for charge transport [57, 58]. Earlier, we reported the use of 5,ll-bis(l-naphthyl)indolo[3,2-jb]carbazole, a derivative of 5, as a hole transport material in OLEDs [59]. Because of its sterically encumbered naphthyl substituents, this compound forms only an amorphous film on vacuum deposition, and mobility is low in OTFTs, as expected. 

If the temperature dependence of the electronic conductivity of a semiconductor is to be accounted for, it is necessary to analyse how the density of charge carriers and their mobilities each depend upon T (see Eq. (2.25)). In the first place attention will be confined to the density n of electrons in the conduction band and the density p of holes in the valence band. When the intrinsic properties of the crystal are under consideration, rather than effects arising from impurities or, in the case of compounds, from departures from stoichiometry, the corresponding conductivity is referred to as intrinsic conductivity . The approach to the calculation of n and p in this instance is as follows. 

---