Colour tunability of polymeric light-emitting diodes with top emission architecture
Polymeric light-emitting diodes (PLEDs) have been fabricated with top emissive architecture and a shift of the light emission wavelength is observed for a single emitting material—phenyl-substituted poly(p-phenylenevinylene) (Ph-PPV). The device is built on a glass substrate and its structure consists of a bi-layer anode (including a high reflective metal thin film and indium tin oxide anode—ITO thin film), polymer stack and semitransparent multi-layer cathodes. Poly(styrene sulfonate)-doped poly(3,4-ethylene dioxythiophene) (PEDOT: PSS) and Ph-PPV are employed as the hole transport layer and light-emitting layer, respectively. Changes in the electroluminescence (EL) characteristics of the PLEDs are examined by adjusting the ITO thickness. The EL peaks of the devices with a single emissive layer have a wide variation in the wavelength range, from 547 to 655 nm, due to the different ITO thicknesses.