Effect of ethanolamine passivation for ZnO nanoparticles in quantum dot light emitting diode structure

摘要： Aging effect of ZnO nanoparticles in quantum dot light-emitting diode (QD-LED) structure is studied. Coarsening of as-synthesized ZnO nanoparticles is observed in both solution and thin film structure, which potentially deteriorates device performance of QD-LED over time. Firstly, temperature effect on ZnO coarsening is investigated, and it reveals that ripening of ZnO nanoparticles is faster at higher temperature due to its diffusion controlled mechanism of nanoparticle coarsening. To observe aggregation of the ZnO in the film state, electron transporting part (ZnO/Al) of QD-LED structure was prepared. Current densities of the ZnO film and electron only device (QD/ZnO between two electrodes) are also measured. Resistance of the film increased as a function of aging time, which corresponds to optical microscopy observation of ZnO film. Aggregation of ZnO nanoparticles was directly measured by root-mean-square value in atomic force microscopy. Ethanolamine (EA) stabilizer is added in the ZnO solution to disperse the ZnO nanoparticles without aggregation. The effect of EA on the surface passivation of the ZnO was revealed by scanning electron micriscopy observation directly by suppressed pinhole formation. Finally, device lifetime was measured for QD-LED with EA stabilized ZnO to understand the effect of ZnO aging on long term QD-LED device operation.