Fully Enclosed Composite Micro/Nano-Package for High-Quality Micro-LED Display Pixels and In Situ Nanoimprint Technology

Micro/mini-light emitting diode (LED) arrays are regarded as the most promising next generation of display devices. However, the inherent Lambertian radiation of LED chips results in a significant pixel crosstalk. To improve the display quality, high-quality micro/mini-LED display pixels with fully enclosed composite micro/nano-packages and in situ nanoimprint technology are proposed and demonstrated in this work. The nanoimprint template is designed as a composite structure comprising an intermediate sandwich cavity array and thin-bottom nanostructure layer. Contact is maintained between the template and LED chips array substrate. By vacuuming the sealed sandwich cavities, the thin-bottom nanostructure layer is deformed to drive the upward protrusion of the liquid optical polymer. Moreover, the nanocavities on the thin nanostructure layer are fully filled by the polymer, forming a composite micro/nano-package. The characteristics of the composite micro/nano-package, such as the aperture and protrusion height, can be flexibly adjusted by changing the template structure or process parameters. A 6 x 8 array LED chips display device enclosed by a composite micro/nanopackage is developed. The divergence angle of the single LED chip decreases to 72 degrees from the original 138 degrees, the light-extraction efficiency increases18.4%, and the luminescence spectrum and current-voltage characteristics changes only minimally. Pixel crosstalk resulted by the inherent Lambertian radiation of LED chips significantly hiders the quality of mini/micro-LED display devices. Fully enclosed composite micro/nano-package structure and in situ nanoimprint technology is proposed in this paper. By composite micro/nano-packaging, the divergence angle of the single pixel decreases to 72 degrees, and the light-extraction efficiency increases 18.4%.image