Efficient Quantum Dot Color Conversion Layer with Mixed Spherical/Rod-Shaped Scattering Particles

A quantum dot (QD) color conversion layer (CCL) with mixed-shaped scattering nanoparticles exhibits enhanced light conversion and reduced blue leakage in QD-organic light-emitting diodes (OLEDs). In this study, nontoxic bright red QDs and spherical and rod-shaped zinc oxide (ZnO) nanoparticles were mixed in an ultraviolet-curable resin without aggregation. The mixture of spherical and rod-shaped ZnO nanoparticles enhanced the blue light scattering inside the QD CCL, which results in an increase of the blue absorption by the QDs and a dramatic improvement of the color conversion. Extraction of the converted red light was also attributed to the Mie scattering of the rod-shaped scattering nanoparticles. The QD CCL with 15 wt % mixed-shaped scattering particles showed seven times increase of red intensity and four times decrease of blue intensity compared to that without scattering particles. We fabricated direct coat-type QD-OLEDs and confirmed that the color conversion and output/input efficiencies were improved and the blue leakage was decreased with increasing number of QD CCLs. This method improves the color conversion efficiency without increasing the amount of QDs and reducing the blue leakage without using a color filter.