Synergistic Effects of Surface Ligand Engineering and Double Matrices Protecting Enable Ultrastable and Highly Emissive Blue/Cyan Perovskite Nanocrystal Films for Multifunctional Applications

Abstract

Perovskite nanocrystals (NCs) have attracted considerable attention because of the extraordinary optoelectronic properties, making them promising candidates for lighting and display applications. However, the emissive efficiency and stability of blue/cyan-emitting NCs lag far behind other color emissive perovskites, which greatly restrict their practical application. Herein, a feasible strategy is proposed for synthesizing highly luminescent and stable CsPbCl x Br 3−x NCs by the didodecyldimethylammonium bromide (DDAB) ligand-assisted post-treatment. The prepared DDAB-CsPbCl 0.8 Br 2.2 and DDAB-CsPbCl 2.0 Br 1.0 NCs exhibit bright cyan and blue emission, respectively, and their quantum yields are significantly enhanced from 12.2% and 7.5% to 83.1% and 75.3% owing to the obvious decrease of surface defects by the ligand-exchange and halogen-compensation mechanisms. The outstanding fluorescence properties are almost remained by grafting perovskite NCs onto the surface of SiO 2 nanospheres. Notably, the ultrahigh water-stability is realized after encapsulating the composite nanospheres into polystyrene-polyisoprene-polystyrene (SIS) film, which is benefit from the triple protection of DDA + cations, SiO 2 nanospheres and SIS copolymers. The fabricated SiO 2 @DDAB-CsPbCl 2.0 Br 1.0 /SIS film is assembled into an white light emitting diode with high color rendering index of 83.4. Importantly, the blue/cyan-emitting films display superb temperature-sensitivity (30-160 °C) and favorable elasticity (1200% stretch rate), indicating their promising application prospect in flexible multifunctional photoelectric devices.

Polymer‐Encapsulated Halide Perovskite Color Converters to Overcome Blue Overshoot and Cyan Gap of White Light‐Emitting Diodes

“…[20] Very recently, Hu et al prepared DDAB-CsPbCl 0.8 Br 2.2 PNCs exhibit bright cyan emission, and the PL QYs are enhanced from 12.2% to 83.1% owing to the decrease of surface defects by the ligand-exchange and halogen-compensation mechanisms. [19] Nevertheless, the progress of application of the above cyan PNCs as a solid state component in WLED lighting devices is still limited. Moreover, the long-term working stability that needs to be addressed in the practical applications remains a huge challenge.…”

“…At present, the most popular WLEDs utilized the blue‐emitting InGaN LED chips (440–460 nm) and YAG:Ce 3+ yellow‐emitting phosphors (520–700 nm) to produce white light lighting, resulting the “blue overshoot” in the ≈440–460 nm range and the “cyan gap” in the ≈470–520 nm range, as shown in Figure . [ 3–5,7–21 ] Recently, many studies have shown that excessive exposure to intense 440–460 nm blue light may increase optical damage to the human eye, leading to depression and psychological problems. [ 22,23 ] In the meantime, “full‐visible‐spectrum lighting” has been proposed to obtain a high‐CRI light source that can mimic natural sunlight.…”