Designing the next generation of high-resolution displays requires high pixel density per area and small pixel sizes without compromising the optical quality. Quantum dots (QDs) have been demonstrated as a promising material system for down-conversion of blue emission as they provide pure colors on the wide color gamut. However, for high color-conversion efficiency, the required QD film thickness has not been compatible with small pixel sizes. In this work, we develop a new type of freestanding QD-based color converter for efficient optical down-conversion from inorganic blue light-emitting diodes (LEDs) in a color-by-blue configuration. CdSe/ZnS core-shell QDs in a UV-curable polymer matrix are encapsulated within cavities formed by patterning and bonding a pair of patterned quartz substrates. By controlling the required QD thickness and the pixel size independently, we demonstrate freestanding monochrome red and green converters with small pixel sizes down to 5 × 5 μm2 and a high resolution of >3600 ppi. The optical studies show that the QD film thickness required for efficient color conversion can be successfully realized even for the small pixel sizes. We further combine green and red pixels in a single converter to achieve white emission when combined with blue LED emission. The QD color converter design and processing are decoupled from the LED fabrication and can be easily scaled to wafer-size integration with arbitrary pixel sizes for QD-based RGB displays with ultrahigh resolution.
Keywords: CdSe/ZnS core−shell; color converters; freestanding; light-emitting diodes; quantum dots; small pixel size.