Efficient, blue light-emitting diodes using crosslinked polymer multilayers

Single-, double- and triple-layer light emitting diodes (LED) were fabricated from cross-linkable hole transporting arylamine polymer and emissive fluorene polymer, and an oxadiazole trimer using conventional solution casting techniques with the aid of cross-linking to prevent dissolution of the lower layers. Device efficiency, luminance, and color all improve as one goes from single- to double- to triple-layer devices, interpreted in terms of balanced charge injection leading to greater recombination efficiency.