Highly efficient quantum-dot light emitting diodes with sol-gel ZnO electron contact

We demonstrated an efficient inverted CdSe/CdS/ZnS quantum dot light emitting diode (QLED) using sol-gel ZnO (s-ZnO) as the electron-injection layer (EIL). The device performance is comparable to that of a device based on the common used nanoparticle ZnO (n-ZnO) EIL. The peak efficiency (12.5 cd/A) and luminance (13000 cd/m²) for the s-ZnO based device was found to be similar to the n-ZnO based device (11.2 cd/A and 15000 cd/m²). The morphology properties of these two types of ZnO films were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM) measurements. A very smooth surface was achieved for the s-ZnO film. Moreover, the quantum dot (QD) layer on the s-ZnO also possesses high quality with a close packed structure.