Semiconductor/semiconductivity polymers

In comparison with traditional inorganic semiconductors, semiconducting polymers cannot be considered materials with ultra-high purity. As a result, although many device concepts have been demonstrated using semiconducting polymers as the active materials, there has been considerable skepticism that these novel semiconductors could be used in commercial applications. 

Bassler, H. 2000. Charge transport in random organic semiconductors. Semiconducting polymers Chemistry, physics and engineering, eds. G. Hadziioannou and P.E van Hutten. Weinheim Wiley VCH. 

Despite the scientific progress and the demonstration of novel device concepts, there was considerable skepticism that semiconducting polymers would ever reach the levels of purity required for long-lifetime commercial devices. In the context of the last 50 years of semiconductor physics, conjugated polymers were often... 

G Yu and AJ Heeger, Semiconducting polymers as materials for device applications, in The Physics of Semiconductors, M. Schleffer and R. Zimmerman, Eds., World Scientific, Singapore,... 

Note 5 A polymer that shows electric semiconductivity is called a semiconducting polymer (See [2], p. 372 for semiconductor). 

So far we have outlined the conceptual framework in which we discuss charge transfer in organic semiconductors. It is based on a molecular picture where the molecular unit is considered central, with interactions between molecular units added afterwards. For amorphous molecular solids and for molecular crystals this approach is undisputed. In the case of semiconducting polymers, a conceptually different view has been proposed that starts from a one-dimensional (ID) semiconductor band picture, and that is generally known as the Su-Schrieffer-Heeger (SSH) model [21-24]. 

In some ways, however, semiconducting polymers are more robust than their inorganic counterparts. In particular, whereas pinning of the Fermi energy by surface states is a major problem in conventional semiconductors, the Fermi... 

In the spirit of the goal of this review, we focus on those aspects of the science of conjugated polymers that make them unique as NLO materials i.e. on the role of bond relaxation in the excited state (soliton and polaron formation) in the NLO response of conjugated polymers. As emphasized in Section IV, when photoexcited, bond relaxation in the excited state leads to the formation of electronic states within the energy gap of the semiconductor. These gap states change the optical properties of the polymer (photoinduced absorption). In this sense, semiconducting polymers are inherently nonlinear in their optical response. This process is shown schematically in Fig. VE-1. 

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