Successes and Challenges of Core/Shell Lead Halide Perovskite Nanocrystals

Abstract

Newly emerging perovskite nanocrystals (NCs) have shown a huge potential to be utilized in a gamut of optoelectronic devices due to their superior photoluminescence quantum yield (PLQY), tunable emission wavelength, and facile synthesis protocols at low cost. Despite the enormous progress made in synthetic protocol development, their poor stability against environmental stressors remains a major shortcoming that significantly restricts their practical applications and future commercialization. Of particular interest, core/shell NC engineering has fueled significant progress not only to improve the luminescent properties, reduce exciton recombination, suppress non-radiative recombination, and enhance the charge carrier transport but also, perhaps more importantly, to improve the semiconductor materials' stability under harsh environmental conditions. Accordingly, this architecture represents a promising avenue to alleviate the stability issue and, therefore, could push the devices' operational stability and performance forward. In this Focus Review, we explore the successes and challenges of recently reported perovskite core/shell heterostructures and summarize the synthesis methods, the photophysics after shelling, the theoretical approaches, and the applications. Finally, we conclude with a discussion of new opportunities and suggestions to push this research area a step forward.

All‐Inorganic Perovskite Polymer–Ceramics for Flexible and Refreshable X‐Ray Imaging

“…[16,27] Moreover, agglomeration and Ostwald ripening of the perovskite nanocrystals obviously increase the light scattering of the scintillator film, and it also limits the loading concentration of the perovskite nanocrystal scintillators, leading to low scintillation output. [28,29] Although many capping agents, surfactants, ionic liquids, and complicated synthesis techniques are proposed to prevent aggregation, it is still a key problem preventing the growth of uniform distributed inorganic PNCs inside the polymer matrix. [30][31][32][33][34][35] This may attribute to the low viscosity environment (5 × 10 4 cP) [36,37] which provides insufficient resistance for the rapid migration of atoms and PNCs before the solidification of the film.…”

The making of a reconfigurable semiconductor with a soft ionic lattice

“…Even though there has been a growing number of reports on the heterogeneous, core/shell structures of halide perovskites, an atomically defined, epitaxially grown core/shell interface between halide perovskite and another covalent semiconductor has not been realized. [75][76][77] The core/shell geometry, compared with other hetero-structures such as the Janus geometry, has the advantage of protecting the halide perovskite from the attack of polar solvents or humid environments. Resolving the atomic structure of the interface is key to proving whether the heterogeneous interface is coherent or not and demonstrating how interfacial defects, such as dis-locations, are distributed (Figures 4E and 4F).…”

“…The difficulties associated with properly interfacing halide perovskites with other materials have a deep origin in the structural uniqueness of halide perovskites. 8,76,77 The drastic difference in the bonding types between halide perovskites and typical covalent semiconductors results in challenging interfacial engineering. The apparent lattice match is no longer a good criterion for selecting shell material candidates; coordination environments, molecular orbital hybridization, turning terminating halides at the perovskite surface into bridging halide, etc., are all factors to be considered.…”

Suppressing thermal quenching of lead halide perovskite nanocrystals by constructing a wide-bandgap surface layer for achieving thermally stable white light-emitting diodes

“…[8] Despite the recent rapid progress, one critical bottleneck to the practical applications of perovskite LED is the instability of perovskite NCs, which derives from their intrinsically moisture/light/oxygen/heat sensitive ionic structures and low formation energy. [9][10] So far, many great efforts have been made to enhance the stability of perovskite NCs against moisture/light/oxygen, and substantial progresses have been obtained, including compact barrier matrixes encapsulation (SiO2 [11] , Al2O3 [12] , TiO2 [13] , polymeric matrices [14] , etc) and surface engineering strategies [15][16] . However, another often overlooked problem of perovskite NCs is the severe drop in luminescence intensity with increasing temperature (so-called fluorescence thermal quenching), leading to a very adverse impact on practical display application.…”

“…and surface engineering strategies. 15,16 However, another oen overlooked problem of perovskite NCs is the severe drop in luminescence intensity with increasing temperature (so-called uorescence thermal quenching), leading to a very adverse impact on practical display application. [17][18][19][20] Actually, LED devices inevitably generate heat during operation, and their temperature can easily reach 373 K or even higher, 21 which causes the PL emission thermal quenching behaviors of perovskite NCs and leads to color deviation and brightness weakening of the display screen.…”