M. Yan et al., LIMITS TO QUANTUM EFFICIENCY IN ELECTROLUMINESCENT DEVICES BASED ON CONJUGATED POLYMERS, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 256, 1994, pp. 17-25
Excited state dynamics in poly(p-phenylenevinylene) (PPV) have been st
udied by transient absorption and photoluminescence measurements. The
quantum yield of emissive singlet exciton photogeneration is estimated
not to exceed 20 %. This is mostly limited by efficient formation of
non-emissive interchain ''spatially indirect'' singlet excitons analog
ous to those in type II semiconductor heterostructures which decay non
radiatively. We also show that exciton quenching by oxidation defects
is an additional process which can dramatically reduce photoluminescen
ce quantum yield.