A theoretical study of photoluminescence quenching in cis-polyacetylene

The non-radiative decay of photoinduced bond-alternation defects in cis-polyacetylene is considered within the SSH model [18]. The charge-conjugation symmetry of the simplest model Hamiltonian must be violated to explain the low photoluminescent yield (˜ 10-3 %) found experimentally. The simplest such route, that of electron-phonon coupling via second nearest-neighbour hopping is considered. It is found that a multiphonon process is required, the resulting decay rate being very sensitive to the parameters chosen. If this is the dominant non-radiative process, then it gives a potentially highly accurate method of determining the value of α, the nearest-neighbour electron-phonon coupling constant. The results for cis-polyacetylene can be generalized to give a qualitative understanding of photoluminescent properties of more complex conjugated molecules.