Theoretical investigation of the spin-dependent exciton formation rates in polymeric light-emitting diodes

First, a brief review is given, of recent experimental and theoretical progress in the determination of the spin-dependent exciton formation rates in electroluminescent π-conjugated polymers. We then describe our recent development of the coupled-cluster equation of motion method, and present its application to the theoretical study of singlet and triplet exciton formation rates and polymer light-emitting diode quantum efficiency. It is found that, in general, singlet excitons can be formed with a higher yield than triplet excitons. The underlying mechanism is still a matter of debate. Here, we explore the role of inter-chain charge-bond correlation effects.