52.2: Invited Paper: Application of Quantum‐dot Patterned Film with Scattering Nanoparticles for the High Efficiency Displays

Abstract

Quantum dot (QD) as a color converting material in the form of patterned film can effectively improve the optical efficiency of displays. Since all of the light passing through the QD film cannot be fully down‐converted, however, novel structure or materials are required to improve the light down‐converting efficiency in the QD film. TiO2 and wrinkled silica particles are respectively applied as scattering nanoparticles which can increase optical path of light in this study. From experimental results, it was confirmed that optical efficiencies of red and green light in white OLED prepared with QD and TiO2 were enhanced further by 57.3% and 17.5%, respectively. In addition, the QD‐converting efficiency to green light from blue µ‐LED was increased using wrinkled silica‐QD hybrid particles, resulting in the enhanced luminous efficacy of 13.1lm/W with 15wt% QD concentration.

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

“…When 1−3 layers of QD CCL-M were applied, the color conversion efficiencies were 40.7%, 41.3%, and 47.7%, respectively, which are high level when compared with those obtained in previous studies. 17,18,30,32 In the color conversion efficiency expression, because the amount of absorbed light is the denominator, similar values were obtained regardless of the number of layers. When the output/input value was calculated as the ratio of the converted red PL intensity to the incident blue EL intensity, the efficiency increased as the number of QD CCLs increased (SI Table S3).…”

“…This phenomenon has also been revealed in other QD CCL studies on scattering particles, and it is known that the color conversion improvement does not occur well when scattering particles above a certain concentration are included. 30,33,34 Excessive scattering occurs when the ZnO concentration is extremely high which may decrease the blue absorption by the QDs, and thus, decrease the converted red intensities. In addition, as the concentration of the scattering particles increases, the possibility of QD aggregation increases.…”

“…Materials used as scattering particles, such as titanium dioxide (TiO 2 ), silicon dioxide, barium titanium oxide, tin oxide, and zinc oxide (ZnO), should have wide band gaps and should not absorb the OLED and QD light. Thus far, studies on the enhancement in the color conversion efficiency by introducing scattering particles have mainly focused on TiO 2 nanoparticles. − Nanoparticles with sizes smaller than the OLED wavelength have been used to scatter the OLED light by Rayleigh scattering and facilitate their dispersion. − Few studies have been conducted on improving the light conversion efficiency by introducing other light scattering materials. Sun et al.…”

“…QD-OLEDs have all of the advantages of OLEDs, such as small thickness due to self-emission, high brightness, high contrast ratios, and high refresh rates, as well as those of QDs, with excellent color expression. − Thus, far, most studies in the field of QD CCLs have focused on improving the QD synthesis method to enhance the absorption and emission properties of QDs, formulating QD CCL resins, and fabricating QD CCLs. − In particular, to enhance the color conversion efficiency, research has been conducted to increase QD concentration and improve the thickness of QD CCLs. Another approach to increase the color conversion efficiency is to introduce scattering particles, which are considered essential for QD CCLs. − Scattering particles can improve the extraction of the converted color light by increasing the optical path of blue light, resulting in improved absorption of QDs, and finally, enhancing the emission of QDs. Materials used as scattering particles, such as titanium dioxide (TiO 2 ), silicon dioxide, barium titanium oxide, tin oxide, and zinc oxide (ZnO), should have wide band gaps and should not absorb the OLED and QD light.…”

Flexible micro-LED display and its application in Gbps multi-channel visible light communication

“…However, a high concentration of QD in PR solution can hinder the development of the PR film, and polymer residues can remain on the substrate after the process. This issue can be resolved by blending the scattering nanoparticles into the QD-PR solution 28 . TiO 2 nanoparticles exhibit a high refractive index of 2.8 and can be utilized as scattering enhancers in the QD color conversion layers.…”