Barrier-free electron-hole capture in polymer blend heterojunction light-emitting diodes

A novel barrier-free mechanism for electron-hole capture at heterojunctions between two semiconductor polymers is shown to occur in highly efficient light-emitting diodes (LEDs). Electron-hole capture across the heterojunction forms an exciplex-a localized heterojunction state-and subsequent endothermic energy transfer produces highly emissive excitons. This process only requires low charge densities at the interface, enabling excellent LED performance.