Quenching Resonance

Where ToWSOK. This is a very unusual form of dependence on T. Two mechanisms which may contribute to this behaviour are (i) the T-dependence of the polaron spin-lattice relaxation rate f , and (ii) the diffusivity of the trapped polarons. Yet while f i may indeed account for the observed behaviour [23,59], comparison with the weak temperature dependence of the EL- and cr-quenching resonances in PPV-based LEDs (see Section 2.2 below) suggests that the diffusivity is the major mechanism which weakens the spin-dependence of the trapped polaron population as T increases. However, spin-lattice relaxation is suspected to be nonnegligible, in order to account for the unusual dependence given by equation (7.18). 

The response of enhancing and quenching resonances in DOO-PPV to photo-oxidation is shown in Figure 7.30 While the enhancing resonance was... 

The absence of vibronic structure in the PL of CN-PPV and EL of the PPV/CN-PPV bilayer LEDs is also noteworthy, because it is entirely consistent with the foregoing speculations on the nature of the quenching resonance The absence of vibronic structure is consistent with a relatively large number of defects creating a similarly large fraction of short conjugation segments. These defects may be the same as those which induce the fusion of free polarons to bipolarons. If this is the case, a correlation between the vibronic... 

The spectral dependence of the EL-quenching resonance is shown in Figure 7.37(d). Since the resonance is quenching, i.e., negative, the observed behaviour demonstrates that the long-wavelength emission band of the EL, which is absent from the PL, does not contribute to the EL-detected resonance. 

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