Patterning perovskite colour converters for AR/VR microdisplays

TL;DR

We address the challenge of achieving vibrant RGB color at ultra-high resolutions for AR/VR microdisplays via colour-conversion on microLEDs using perovskite nanocrystals. The authors demonstrate three patterning approaches—lift-off, negative photoresist, and dry etching—to define perovskite CC pixels, achieving high optical density $OD/\mu m > 1.0$, narrow emission bands, and red emission peaking at $623$ nm. The results show that perovskite CCs can be patterned in thin ($2$–$3~\mu m$) or thicker pixels, with trade-offs in adhesion, processing compatibility, and cross-talk mitigation, including a metal matrix patterning strategy. These findings support the robustness and manufacturing compatibility of perovskite CC materials for high-resolution AR/VR microdisplays, enabling integrable patterning in standard semiconductor fabs.

Abstract

Colour conversion offers the clearest path to achieve RGB colours in high resolution microdisplays for AR/VR. With resolutions beyond 5000 ppi (i.e. RGB pitch of 5 um), the thickness of the conversion layers is critical for efficiency and manufacturing. Perovskites outperform other conversion materials (quantum dots or phosphors) with their high absorption coefficients for blue light. In this contribution, we show how perovskite materials, engineered for high optical density and colour purity, can be patterned to produce colour converting pixels. We demonstrate patterning using three approaches (lift-off, negative photoresist and dry etch), and discuss their advantages and disadvantages. The results consolidate the choice of perovskites for AR/VR applications by demonstrating their robustness and compatibility with multiple patterning strategies suitable for high resolution microdisplays.

Figures (5)

• Figure 1: Absorption and photoluminescence spectra of typical green (left) and red (right) perovskite thin films.
• Figure 2: Patterning methods for perovskites colour converters (grey: substrate, green: perovskite material, blue: photoresist). See text for details.
• Figure 3: Photoluminescence (a-b, e-f) and SEM images (d) of green perovskites CC pixels patterned via (a, b) lift-off process (pixel diameter 10 µm), (c, d) negative photoresist (pixel diameter 5 µm) and (e, f) dry etching (pixel diameter 10 µm).
• Figure 4: Transmittance and OD at 450 nm for films obtained from green neat and photoresist materials at 450 nm.
• Figure 5: a) Optical profiler image of wells in an aluminium matrix (depth 2.6 µm) and b) photoluminescence micrograph of wells filled with a green perovskite photoresist (position of unfilled wells revealed by white overlay).