We demonstrate the use of self-assembled bionanostructures in polymer light-emitting diodes. Amyloid fibrils formed by protein misfolding were decorated with a soluble luminescent conjugated polymer. This conjugated polymer complex with amyloid fibrils was used as the active layer in a light emitting diode, resulting in a 10-fold increase in external quantum efficiency compared with pristine polymer, because of improved carrier injection. © 2008 American Chemical Society.