The Electronic Structure of PPV

FIGURE 5.2. pz orbitals along a conjugated polymer backbone. 

FIGURE 5.3. Rearrangement of bonding geometry around a negative charge in PPY. 

FIGURE 5.4. Electronic transitions (dotted arrows) due to positive and negative polarons. Occupation of electronic energy levels is denoted by solid arrows. The ground state is shown as a reference. 

FIGURE 5.5. Absorption (circles) and emission (line) spectra of PPV. 

The radiative decay of singlet excitons is clearly an important process in the operation of polymer LEDs. This rate is denoted by kr, where for PPV, (k, rl 1200 ns.19 Radiative decay competes with various nonradiative decay processes, such as quenching of excitons by defects, exciton dissociation, and intersystem crossing to form triplet states. Assuming that both radiative and nonradiative decays are monoexponential, the photoluminescence quantum efficiency, PLeff, defined as the number of photons emitted per photon absorbed, is given by 

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Of particular interest is the electronic structure of PPV at lowest binding energy the region of 0 eV to about —8 eV in Fig. 7.18, where 0 in this case is the vacuum level energy. The similarity with the frontier occupied states of DP7 are as follows. In DP7, the electrons... 

Color Tuning by Substituents, Electronic, and Steric Effects The electronic structures of PPV and ring-substituted derivatives have been the subject of several... 

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