Opto-electronic properties of poly (fluorene) co-polymer red light-emitting devices on flexible plastic substrate

In this paper, we report on the multilayer poly (fluorene) co-polymer red light-emitting devices (PLEDs) fabricated on flexible plastic substrates. An organic hole transport layer (HTL) is inserted between PEDOT:PSS hole injection (HIL) and light-emissive layers (LEL). Since the highest occupied molecular orbital (HOMO) of the HTL is located between those of HIL and LEL, the insertion of HTL reduces the effective HOMO level offset between HIL and LEL, reducing the device operation voltage and producing comparable or better device efficiencies in comparison with the conventional PEDOT:PSS-only devices. Maximum emission efficiency, ∼0.8 cd/A, power efficiency, ∼0.7 lm/W, and external quantum efficiency, ∼1.5%, have been obtained for multilayer red PLEDs.