Coupled-cluster approach for studying the singlet and triplet exciton formation rates in conjugated polymer LED’s

The coupled-cluster equation of motion approach is applied to describe positively and negatively charged states as well as exciton states in conjugated polymers. The formation rates for singlet and triplet excitons associated with intermolecular charge-transfer processes are calculated. It is found that the interchain bond-charge correlation has a strong influence on the singlet/triplet ratio, since the charge-transfer configuration contributes differently to the singlet and triplet excitons. In addition, we find that the range of electron interaction potential has a strong influence on the formation rates. The ratio between the electroluminescence and photoluminescence quantum yields can exceed the 25% spin-degeneracy statistical limit.