All inorganic quantum dot light emitting devices with solution processed
transport layers are investigated. The device consists of an anode, a hole
transport layer, a quantum dot emissive layer, an electron transport layer and a
cathode. Indium tin oxide coated glass slides are used as substrates with the
indium tin oxide acting as the transparent anode electrode. The transport layers
are both inorganic, which are relatively insensitive to moisture and other
environmental factors as compared to their organic counterparts. Nickel oxide
acts as the hole transport layer, while zinc oxide nanocrystals act as the
electron transport layer. The nickel oxide hole transport layer is formed by
annealing a spin coated layer of nickel hydroxide sol-gel. On top of the hole
transport layer, CdSe/ZnS quantum dots synthesized by hot injection method is
spin coated. Finally, zinc oxide nanocrystals, dispersed in methanol, are spin
coated over the quantum dot emissive layer as the electron transport layer. The
material characterization of different layers is performed by using absorbance,
Raman scattering, XRD, and photoluminescence measurements. The completed device
performance is evaluated by measuring the IV characteristics,
electroluminescence and quantum efficiency measurements. The device turn on is
around 4V with a maximum current density of ∼200 mA/cm2 at
9 V.