Uniformity and Stability of Quantum Dot Pixels Evaluated by Microscale Fluorescence Spectroscopy

Abstract Quantum dot color conversion films (QD‐CCFs) are proposed for use in full‐color micron‐sized light‐emitting diode (micro‐LED) displays, but quickly and precisely evaluating their optical quality and identifying the bad pixels among them remain challenging. In this work, microscale fluorescence spectroscopy (MFS) is demonstrated to investigate the photoluminescence uniformity and stability of red‐emitting CdSe/CdS/ZnS QD‐CCF pixels prepared by high‐resolution inkjet printing. The photoluminescence (PL) intensity imaging, together with the PL spectrum, lifetime imaging, and time‐dependent PL intensity curve, enables accurate analysis of the luminescence uniformity and thermal and light stability of QD‐CCFs. The coffee rings in QD‐CCF pixels can be clearly identified by MFS, which are missed by a conventional fluorescence microscope. It thus provides feedback for tailoring the composition and properties of ink to eliminate coffee rings or other defects. The combination of MFS with machine learning will likely realize the “massive detection” of QD‐CCFs for micro‐LEDs.