Energy conjugated polymers

For a junction of a conjugated polymer, which has an energy gap of around 3 eV (around the value of the polyphenylenes) and a free carrier concentration n> 1017 cm-3, with a low workfunction metal (e.g. when [Pg.155]

The PES measurements arc performed with reference to the Fermi level of the photoclectron spectrometer, in solid specimens, as dealt with here, by the way the spectroscopy works. Thus, in cases when the Fermi level shifts due to some chemical modifications of the sample, i.e., in the intercalation of graphite or other layered compound [16] or in the doping of conjugated polymers 1171, il is necessary to account for the change in the Fermi energy level before interpreting spec-... 

The proposed scenario is mainly based on the molecular approach, which considers conjugated polymer films as an ensemble of short (molecular) segments. The main point in the model is that the nature of the electronic state is molecular, i.e. described by localized wavefunctions and discrete energy levels. In spite of the success of this model, in which disorder plays a fundamental role, the description of the basic intrachain properties remains unsatisfactory. The nature of the lowest excited state in m-LPPP is still elusive. Extrinsic dissociation mechanisms (such as charge transfer at accepting impurities) are not clearly distinguished from intrinsic ones, and the question of intrachain versus interchain charge separation is not yet answered. 

Figure 10-15 shows the output vs. input energy relation with a clear threshold at a pump pulse energy of approximately 1.5 nJ. This value is an order of magnitude lower than the threshold for the observation of ASE in simple planar waveguides, i.e. without distributed feedback but prepared with the same conjugated polymer. 

---