Organic semiconductor ionization potential

It has been shown [80] that organic semiconductors with the lowest redox potentials (which reflect the ionization potentials) of —0.2 V and 0.2 V vs SSCE for PPy and PANI, respectively, interact reversibly with ammonia. However, other polymers, such as PT (0.7 V), PA (0.7 V) and poly(para-phenylene) (PPP) (1.6 V) [81], all have higher redox potentials and their interaction is reported to be irreversible. The reversible changes of the transitions in the optical spectra correspond to the doping/undoping process. The results obtained on PT films, upon exposure to NO2, SO2 [82], or on PPy films during their exposure to NH3 [83], or on PPy and PPP films... 

The interface between the quasi-metal PEDOT PSS and organic semiconductors has been investigated in numerous experiments. As illustrated in Figure 14.16, the energy barrier for hole injection (AE) is not simply determined by the difference between the PEDOT PSS work function (4>) and the ionization potential (/ ) of the semiconductor as predicted by the Schottky-Mott model dipole layer formation at the interface will lead to a vacuum level shift A [158-161]. 

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