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.