Characterization of Light Emitting Devices Based on MEH‐PPV:Quantum Dot Blend Layers

A series of light emitting devices (LEDs) that consisted of a conjugated polymer poly [2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) or blend of MEH‐PPV and CdSe/ZnS quantum dot (QD) emitting layer (EML), an electron‐transporting tris‐(8‐hydro‐xyquinoline)aluminum (Alq 3 ) layer and with/without a hole‐transporting poly( N , N ′‐bis(4‐butylphenyl)‐ N , N ′‐bis(phenyl)benzidine) (poly‐TPD) layer were fabricated and their operation characteristics were investigated. All the fabricated devices showed unnoticeably effect of QDs on electroluminescence spectra that originated from MEH‐PPV. However, the operation currents of LED devices that involved QDs in MEH‐PPV EML were significantly suppressed. This can be attributed to a large amount of charge confinement in QDs which limits current flow through the devices.