Organic-inorganic Perovskite Nanocrystals Research Articles

Blue-emitting perovskite nanocrystals with enhanced optical properties through using NaBH4

APbX3-type [A = CH3NH3 + (MA+), NH2CH=NH2 + (FA+), X = Cl–, Br–, I–] organic–inorganic perovskite nanocrystals (PeNCs) have superior optical properties, such as emission with a narrow full width at half maximum and emission color tunability over the entire visible range. However, blue-emitting PeNCs [APb(Br/Cl)3] exhibit low photoluminescence quantum yields owing to Cl defects, hindering their practical applications. The Cl defects induce nonradiative recombination caused by the trap levels formed deep in the band gap. Herein, we report the preparation of blue-emitting PeNCs that exhibit excellent optical properties by using NaBH4 to decrease the number of Cl defects.

Ultrastable, Deformable, and Stretchable Luminescent Organic-Inorganic Perovskite Nanocrystal-Polymer Composites for 3D Printing and White Light-Emitting Diodes.

Organic-inorganic perovskite nanocrystals with excellent optoelectronic properties have been utilized in various applications, despite their stability issues. The perovskite materials are sensitive to environments such as polar solvents, moisture, and heat. Thus, they are not used for extrusion three-dimensional (3D) printing, as it is usually conducted in the ambient environment and requires heating to liquefy the printed materials. In this work, 11 thermoplastic polymers conventionally used for extrusion 3D printing were investigated to test their capability as protective encapsulation materials for perovskite nanocrystals. Three of them exhibited good protective properties, and one (polycaprolactone, PCL) of these three could be blended with perovskite nanocrystals to form perovskite nanocrystal-PCL composites, which were deformable and stretchable once heated. Because of the low melting point of PCL, the perovskite nanocrystals maintained their optical properties after 3D printing, and the printed objects were still having fluorescent behavior. Moreover, fluorescent micrometer-sized fibers based on the perovskite nanocrystal-PCL composites could also be simply prepared using cotton candy makers. Perovskite nanocrystal-PCL composite films with different emission wavelengths were incorporated with blue light-emitting diodes (LEDs) to realize white LEDs with Commission Internationale de l'Éclairage chromaticity coordinates of (0.33, 0.33).

Mechanism of Photoluminescence Intermittency in Organic-Inorganic Perovskite Nanocrystals.

Lead halide perovskite nanocrystals have demonstrated their potential as active materials for optoelectronic applications over the past few years. Nevertheless, one issue that hampers their applicability has to do with the observation of photoluminescence intermittency, commonly referred to as "blinking", as in their inorganic counterparts. Such behavior, reported for structures well above the quantum confinement regime, has been discussed to be strongly related to the presence of charge carrier traps. In this work, we analyze the characteristics of this intermittency and explore the dependence on the surrounding atmosphere, showing evidence for the critical role played by the presence of oxygen. We discuss a possible mechanism in which a constant creation/annihilation of halide-related carrier traps takes place under light irradiation, with the dominant rate being determined by the atmosphere.