Ultrahigh Resolution Pixelated Top‐Emitting Quantum‐Dot Light‐Emitting Diodes Enabled by Color‐Converting Cavities

Abstract

Realizing pixelated quantum‐dot light‐emitting diodes for high‐resolution displays remains a challenging task because of the difficulty of fine patterning the quantum‐dots. In this study, instead of patterning the quantum‐dots, the color‐converting cavities for realizing high‐resolution pixelated emission are developed. By defining the thicknesses of the transparent electrodes (phase tuning layers) through a photolithographic process, the resultant cavities can selectively convert the unpatterned quantum‐dot white emission as saturated red, green, and blue emission with a brightness of 22170, 51930, and 3064 cd m−2 at 5.5 V, respectively. The developed method enables the realization of ultrahigh density red, green, and blue emission for a display with a resolution of ≈1700 pixel‐per‐inch and a color gamut of 111% National Television System Committee; together with the advantages of quantum‐dot patterning‐free, color‐filter‐free and high brightness, the demonstrated architecture could find potential applications in various displays ranging from cell phone to emerging virtual reality and augmented reality displays.

Full-Color Quantum Dot Light-Emitting Diodes Based on Microcavities

“…In white organic light-emitting diodes (OLEDs), color filters, a distributed Bragg reflector (DBR), and patterned ITO cavity spacers have been used to fabricate the full-color OLEDs [23], in which there is still room to further improve the color purity for display applications. Very recently, the QD hybrid OLEDs [24] and the pixelated QLEDs [25] with cavities for highresolution displays were also realized. For most bottomemitting structures, because the ITO spacer is located between the EML and the glass, which has a low reflectance, there is a concern in the modulation of the microcavity.…”

Acid–Base Reaction-Assisted Quantum Dot Patterning via Ligand Engineering and Photolithography

“…29 Compared with other patterning methods, photolithography can form uniform high-resolution patterns. 30 However, the properties of QDs degrade when they are exposed to harsh chemicals such as photoresist (PR) and developing or lift-off solvents in the photolithography process because of the reactive and large surface area of QDs. These can induce trap sites on the surface of the QDs, which causes nonradiative decay and leads to deterioration of the optical properties.…”

“…Inkjet printing can produce devices by forming a pattern with a small amount of QD ink; however, there is a limitation with respect to resolution, and it is difficult to form a uniform pattern because of the coffee-ring effect . Compared with other patterning methods, photolithography can form uniform high-resolution patterns . However, the properties of QDs degrade when they are exposed to harsh chemicals such as photoresist (PR) and developing or lift-off solvents in the photolithography process because of the reactive and large surface area of QDs.…”

Top-Emitting Microcavity Light-Emitting Diodes Based on All-Thermally Evaporated Lead-Free Copper Halide Self-Trapped-Exciton Emitters

“…35,41 Therefore, the higher EQE and higher color purity of lead-free metal halide LEDs could be achieved with top-emitting microcavity structures. Furthermore, microcavity LEDs based on broadband emission have been noted to obtain separated color outputs with different cavity lengths, 42 suggesting a promising way for STE LEDs to achieve full-color display.…”

“…In addition to material design, a top-emitting LED (TE-LED) structure with a microcavity is another approach to enhancing EL emission by improving the light out-coupling efficiency, − because in the top-emitting microcavity structure, the emitter is sandwiched between a reflective bottom electrode and a semitransparent top electrode; when the optical length of the microcavity matches the emitting wavelength, the emitter in the resonant microcavity could produce narrowed and enhanced emission due to the microcavity effect. , Therefore, the higher EQE and higher color purity of lead-free metal halide LEDs could be achieved with top-emitting microcavity structures. Furthermore, microcavity LEDs based on broadband emission have been noted to obtain separated color outputs with different cavity lengths, suggesting a promising way for STE LEDs to achieve full-color display.…”