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1. NN-LABS Introduction In the past & 5 years, QD-LCD has been rapidly gaining market share, [1] and high performance and solution-processed QLEDs are widely accepted as the next- generation technology for display. [2] For QD-LCD, QDs are down-conversion photoluminescence emitters. For QLEDs, QDs are as electroluminescence emitters. In the information era, display is the main means for humans to communicate with computers. Invention of smart phones promotes display to the central stage of inter-personal connection. For entertainment, display is playing a more and more important role. The territory expansion of display technology in our daily life has a deep root in human nature. The CRT (Cathode Ray Tube) was introduced in the early 20th century and almost completely replaced by LCD and LED technologies. LCD initiated a new paradigm of flatpanel and portable display, [3] which is further advanced by introduction of GaN blue-LEDs and yellow phosphors as the back-lighting-unit. LEDs with organic dyes as emitters (OLEDs) brought in flexible display. [4] Both LCD and OLEDs are deeply involved with chemistry in this traditionally physics-dominating industry. From a viewpoint of materials chemistry, efficient, stable, color-accurate, and colorpure emissive materials are one of the fundamental factors driving display technology innovation. Colloidal QDs are nanometer-size fragments of bulk semiconductor single crystals with their sizes in the quantum confinement regime. [5] Because of quantum confinement, emission color of QDs with a given chemical composition can be tuned in a large optical window, which is the first key advantage of QDs for display applications. The second key advantage is their thermodynamically-stable single-crystal line lattice with thousands to millions of equivalent bonds, making their emission color exceptionally pure (narrow emission peak) and stable under intensive photo-irradiation and heating. Solution processibility is the third key advantage, implying low processing cost and compatibility with diverse chemical media. In literature, there are numerous reviews on either QDLCD or QLED display. [1,6] This article would thus not try to cover the entire ground of either of the two fields. Instead, it would concentrate on the materials chemistry of QDs as emitters in both technologies. Simply for convenience, if possible, we would mostly rely on experimental results in our own hands. NN-Labs https://nn-labs.com/ Phone: +1-479-595-0662

2. Biological basis of vision and implications to emitters for display Vision In a vision process of a normal human eye, light enters the cornea and is focused by the lens onto the retina located at the back of the eye, which is then converted into neuronal signals for the brain to produce an image. Cone cells in retina wS1F ork under normal day-light environment and are responsible for photopic vision with color perception, which is the one related to modern display technology. The color perception of the world for humans relies on three sub-classes of cones with different photoreceptive proteins. Each type of photoreceptive proteins has its own response function to light stimuli (Figure 1 a) and is thus, respectively called blue-cones, green-cones, and red-cones according to the peaks of their wavelength-resolved response curves. [7, 8] Our brain collects signals from the three channels and forms perception of color of a specific vision. An ideal display needs to work on the vision mechanism discussed above and should deliver a picture with exactly the same color information of a colorful object. Picture delivered by a visual display is required to meet the functions of normal human eye in aspects of brightness, color, contrast, resolution, etc. These metrics further expose requirements for emissive materials in display. Note: It is important to mention that the availability and nanoparticles for sale purposes may vary and would depend on the market and regulatory factors. For information on purchasing nanoparticles, it is advisable to consult with specialized suppliers or manufacturers in the field. NN-Labs https://nn-labs.com/ Phone: +1-479-595-0662