Fig. 1. (a) Schematic illustration of the AJ system. (b) The PL emission spectra of QDs with emission wavelengths of 450, 535, and 630 nm.

Fig. 2. AJ red QD NCTU pattern observed by (a) optical microscopy, (b) fluorescence microscopy, and (c) the measured height of the deposited red QD by laser microscopy.

Fig. 3. (a) Optical microscopy image of PR square windows with the pixel size of 35  μm×35  μm, where the pitch is about 40 μm. (b) The laser scanner microscope image of the PR square wall, where the height of the wall is 11.46 μm.

Fig. 4. Process flow of the full-color microdisplay. (a) The structure of the micro-LED arrays. (b) Aligning the mold to the UV micro-LED array. (c)–(e) Consequently jetting the RGB QDs inside the mold window to form the full-color pixels.

Fig. 5. Alignment approach. (a) The OM image focused on the micro-LED array and the defined alignment cross in a sticking position. Parts (b) and (c) show the OM image focused on the PR mold and the location moved to align the alignment cross, respectively.

Fig. 6. (a) Microscope image of the full-color micro-LED after jetted QDs in the PR mold. (b) The RGB pixel array observed by fluorescence microscopy. (c) The fluorescence microscopy image of the jetted QD pixels without the PR mold.

Fig. 7. (a) Top-view image of the micro-LED layout with the pitch of 40.2 μm defined as the intended channel. (b) Our previous work by the QD lines without the PR mold for the microdisplay, which caused cross talk. (c) The QD droplets jetted in the PR mold to confine the size and resolve the cross-talk effect.

Fig. 8. (a) Mechanism of the coffee ring effect due to the QDs’ outward flow during evaporation. (b) Mechanism of the solution to reduce the coffee ring effect by the PR mold. (c) The OM image denoted that the coffee ring effect can be observed when the QD drops were jetted on the GaN substrate. (d)The PR square can confine the QD drops in the hole and resolve the coffee ring effect.

Fig. 9. (a) Reflectance spectrum of 17.5 pairs of the HfO2/SiO2 DBR. (b) The measured EL spectrum of jetted RGB QDs by AJ on a UV micro-LED array, where the black and red lines represent the devices with and without the DBR, respectively.

Fig. 10. (a) A row of the RGB pixel has been driven individual addressable. (b) The full-color micro-LED in full operation and with the DBR layer covered.

Fig. 11. Images of the full-color microdisplay in operation to individually drive the (a) single blue pixel, (b) single green pixel, and (c) single red pixel.