Polymer bilayer structures prepared by evaporative spray deposition from ultradilute solution technique and those characteristics in polymer light-emitting diodes

We prepared polymer bilayer structures, which are consisted of two π-conjugated polymers soluble in tetrahydrofuran, by Evaporative Spray Deposition from Ultradilute Solution (ESDUS) in two temperature conditions (80°C or 65°C) of substrates during the top-layer (CN-PDHFV) deposition. The polymer light-emitting diodes (PLEDs) were fabricated with them. The external quantum efficiency of device A (80°C) tends to be constant throughout a wide current region, whereas that of device B (65°C) increases gradually as current density is getting higher. These observations indicate that ESDUS in 80°C of the top of a substrate enables to form a polymer heterojunction without dissolving in a preceding PFO leyer.