Influence of copolymer interface orientation on the optical emission of polymeric semiconductor heterojunctions.

We have examined the Coulombic interactions at the interface in a blend of two copolymers with intramolecular charge-transfer character and optimized band offsets for photoinduced charge generation. The combination of both time-resolved measurements of photoluminescence, and quantum-chemical modeling of the heterojunction allows us to show that relative orientation across the heterojunction can lead to either a repulsive barrier ( approximately 65 meV) or an attractive interaction which can enhance the charge-transfer processes. We conclude that polymer orientation at the heterojunction can be as important as energy-band offsets in determining the dynamics of charge separation and optical emission.