Naphthalimide side-chain polymers for organic light-emitting diodes : band-offset engineering and role of polymer thickness

TLDR: In this paper, a green light-emitting diodes using a side-chain random polymer based on a high electron affinity naphthalimide moiety (PNI) was reported.

Abstract: We report the fabrication of efficient green light-emitting diodes using a side-chain random polymer based on a high electron affinity (EA) naphthalimide moiety (PNI) The chromophore is attached to a polymethacrylate backbone through a spacer, and emits in the green with high efficiency (30% photoluminescence quantum yield) In single-layer light-emitting diodes (LEDs), we find that the electroluminescence quantum efficiency is not limited by Al cathodes as for poly(p-phenylene vinylene), PPV, and we attribute this to the increased EA We also report maximum internal quantum efficiencies of about 17% for Ca and 09% for Al in double-layer devices where PPV serves as both hole injector and emitter Compared to some oxadiazole based electron injection/transport layers, PNI gives higher efficiencies at high currents, and longer lifetimes Tuning of emission in the red is possible by dye doping (at high concentration) the PNI and causing the emission to happen in this layer We discuss the properties of the