Figure 2. (a) CIE 1931 colour space chromaticity diagram, showing colour space of sRGB, DCI-P3 and Rec. 2020 standards. (b) Comparison of colour space coverage between 2019 models of Samsung QLED Q900R and LG OLED C9 televisions with DCI-P3.
However, it is clear that a considerable fraction of the observable and nature occurring colours are still missing from the DCI-P3 standard. Therefore, there is a significant demand to move towards the Rec. 2020 colour standard, which encompasses 100% of the Pointer’s gamut (natural occurring colours), bringing absolute realism to displays. Displays that can fulfill the Rec. 2020 standard are capable of producing more realistic colours, which remarkably enhances the viewing experience for televisions, computer monitors, smartphones, tablets or advanced tech gadgets such as augmented reality or virtual reality devices. There are, however, no competitive solutions available for achieving Rec. 2020 standard, not unless the light-emitters employ toxic cadmium.
A new semiconductor based on lead halide perovskites (e.g. CsPbBr3 and MAPbI3) has recently emerged as a highly-promising candidate towards fulfilling the Rec. 2020 standard in colour displays.
In 2014, Prof Tan Zhi Kuang, co-founder of Nanolumi, discovered that perovskite semiconductors are capable of exhibiting strong luminescence and successfully developed the first functional perovskite-based light-emitting diodes (Z. K. Tan et al. Nature Nanotechnology 9, 687).1 In this early work, perovskite was shown to be capable of emitting light in a variety of colours through the tailoring of its halide composition, and electroluminescence in the near-infrared, green and red were successfully demonstrated.
In early 2015, Prof Tan and coworkers further reported the formation of perovskite nanocrystals through the blending of perovskite precursors within an organic matrix, and successfully demonstrated wavelength tuning through size control2 as well as showed strong electroluminescence from the nanocrystal-based devices.3 At around the same time, the group of Kovalenko reported a convenient chemical synthesis method to produce colloidal perovskite nanocrystals that can be tuned to emit across the entire visible spectrum at remarkably high efficiencies.4 In early 2016, Prof Tan and coworkers employed colloidal nanocrystals in LEDs and reported high electroluminescence quantum efficiencies of 5.7%, which was then the champion LED efficiency amongst other reports (see Figure 3a).5 Further research efforts by several groups were successful in pushing device efficiencies in excess of 20%.6-8 Last year, Prof Tan’s group demonstrated highly-efficient large-area devices in both rigid and flexible form-factors (Figure 3b) (X. Zhao. & Z.-K. Tan et al. Nature Photonics).8