Perovskite Nanocrystals Protected by Hermetically Sealing for Highly Bright and Stable Deep‐Blue Light‐Emitting Diodes

Abstract

Metal–halide perovskite nanocrystals (NCs) have emerged as suitable light‐emitting materials for light‐emitting diodes (LEDs) and other practical applications. However, LEDs with perovskite NCs undergo environment‐induced and ion‐migration‐induced structural degradation during operation; therefore, novel NC design concepts, such as hermetic sealing of the perovskite NCs, are required. Thus far, viable synthetic conditions to form a robust and hermetic semiconducting shell on perovskite NCs have been rarely reported for LED applications because of the difficulties in the delicate engineering of encapsulation techniques. Herein, a highly bright and durable deep‐blue perovskite LED (PeLED) formed by hermetically sealing perovskite NCs with epitaxial ZnS shells is reported. This shell protects the perovskite NCs from the environment, facilitates charge injection/transport, and effectively suppresses interparticle ion migration during the LED operation, resulting in exceptional brightness (2916 cd m−2) at 451 nm and a high external quantum efficiency of 1.32%. Furthermore, even in the unencapsulated state, the LED shows a long operational lifetime (T50) of 1192 s (≈20 min) in the air. These results demonstrate that the epitaxial and hermetic encapsulation of perovskite NCs is a powerful strategy for fabricating high‐performance deep‐blue‐emitting PeLEDs.

Surface and Interface Engineering for Highly Stable CsPbBr3/ZnS Core/Shell Nanocrystals

“…In addition, the diffraction peak of the ZnS phase is absent in the XRD pattern of d-CsPbBr 3 /ZnS core/shell NCs, which suggests the formation of an extremely thin ZnS shell layer and the absence of other crystalline impurities. 42,60,61 The TEM image of d-CsPbBr 3 /ZnS NCs illustrated in Figure 2b suggests their uniform morphologies consisting of cubic shapes with a narrow size distribution (average size: 11.9 nm). The HRTEM image of a single NC from Figure 2b is presented in Figure 2c, and the clear lattice fringes indicate its well-defined crystallinity.…”

Making and Breaking of Exciton Cooling Bottlenecks in Halide Perovskite Nanocrystals

“…70 The realization of epitaxially grown shells for PNCs is hindered by the perovskites' ionic nature, highly labile surfaces, and stringent lattice mismatch requirements that make epitaxial shell growth challenging. 96,97 However, recent efforts have paid off in realizing PNCs with epitaxially grown ZnS shells, 98 showing promise for further development of stable core−shell PNCs. Furthermore, investigations of interexciton state intraband relaxation, which is a common theme in HC studies of conventional semiconductor QDs, 58,[68][69][70]99 are still relatively unexplored in PNCs.…”

“…Lastly, the presently reported HCC lifetimes are <1 ps, which still need to be decelerated further (at least to hundreds of picoseconds) to be usable in HCSCs. , One promising strategy that could be adopted is in the engineering of core–shelled PNCs with inorganic epitaxial protective shells, which has been shown to reduce the HCC rate dramatically in a pioneering work on CdSe NCs . The realization of epitaxially grown shells for PNCs is hindered by the perovskites’ ionic nature, highly labile surfaces, and stringent lattice mismatch requirements that make epitaxial shell growth challenging. , However, recent efforts have paid off in realizing PNCs with epitaxially grown ZnS shells, showing promise for further development of stable core–shell PNCs. Furthermore, investigations of interexciton state intraband relaxation, which is a common theme in HC studies of conventional semiconductor QDs, ,− , are still relatively unexplored in PNCs.…”

Metal Halide Perovskite: A Promising Materials for Light Emitting Diodes

“…Compared with the organic cap layer, the inorganic shells have more advantages, for example, good conductivity and stability [111]. Lee et al [122] utilized CsPbBr3 PeQD as seed, through blended the seed with ZnCl2, ZnBr2 and S-ODE, the CsPb(Br1-xClx)3 PeQD covered with a ZnS shell was obtained due to low lattice mismatch (Figure 7d). The ZnS shell protected the CsPb(Br1-xClx)3 core from the external effect, accelerated the carrier injection and restricted the ion migration of mixed-halide.…”