Improving the Stability of Metal Halide Perovskite Quantum Dots by Encapsulation

Abstract

Metal halide perovskite quantum dots (PQDs), with excellent optical properties and spectacular characteristics of direct and tunable bandgaps, strong light‐absorption coefficients, high defect tolerance, and low nonradiative recombination rates, are highly attractive for modern optoelectronic devices. However, the stability issue of PQDs remains a critical challenge of this newly emerged material despite the recent rapid progress. Here, the encapsulation strategies to improve the stability of PQDs are comprehensively reviewed. A special emphasis is put on the effects of encapsulation, ranging from the improvement of chemical stability, to the inhibition of light‐induced decomposition, to the enhancement of thermal stability. Particular attention is devoted to summarizing the encapsulation approaches, including the sol–gel method, the template method, physical blending, and microencapsulation. The selection principles of encapsulation materials, including the rigid lattice or porous structure of inorganic compounds, the low penetration rate of oxygen or water, as well as the swelling–deswelling process of polymers, are addressed systematically. Special interest is put on the applications of the encapsulated PQDs with improved stability in white light‐emitting diodes, lasers, and biological applications. Finally, the main challenges in encapsulating PQDs and further investigation directions are discussed for future research to promote the development of stable metal halide perovskite materials.

Enhanced Thermal Stability of Halide Perovskite CsPbX3 Nanocrystals by a Facile TPU Encapsulation

“…However, the applications of CsPbX 3 (X = Br, I, Cl) NCs have been severely hindered by the issue of the stability, mainly derived from thermal degradation and atmospheric moisture . To address this issue, various encapsulation strategies have been proposed to protect perovskite NCs from decomposition in practical applications . Efficient encapsulations can improve their resistance to temperature and/or humidity by introducing an additional matrix to form an isolation between the perovskite materials and atmospheric moisture …”

“…Thermal degradation of perovskite materials is a major bottleneck, which hinders its development especially in areas with high annual average temperatures . Therefore, various encapsulation materials have been studied to alleviate the effects of thermal degradation in recent years.…”

“…CsPbBr 3 QDs were encapsulated using polydimethylsiloxane and were found to be effective in improving the thermal stability of materials . Especially, organic polymers such as polymethyl methacrylate (PMMA)/polycarbonate (PC)/polystyrene (PS) have attracted wide attentions due to their easy processing ability, lighter density, and high flexibility . Another issue in the applications of perovskite materials stems from instability in atmospheric moisture, which greatly limits the actual applications …”

Recent Progress and Development in Inorganic Halide Perovskite Quantum Dots for Photoelectrochemical Applications

“…Inspired by this work, more and more attention has been paid to the IHPQDs with respect to their special structure and unique physicochemical properties for potential applications. Analogous to oxide perovskites, the crystal structure of the IHPQDs has 3D framework, where divalent metal cations (e.g., Pb 2+ , Sn 2+ ) and halide ion (e.g., Cl − , Br − , I −, or mixed halides) form the corner‐sharing (BX 6 4− ) octahedra and the vertexes of the octahedral cavity are occupied by monovalent inorganic cations (e.g., Cs + ) . The framework of IHPQDs no matter in the cubic structure or in the orthorhombic structure formed after partial distortion can make the charge carriers move in the limited 3D grid, thus leading to the relatively high carrier mobility .…”

Optimizing the Atomic Layer Deposition of Alumina on Perovskite Nanocrystal Films by Using O2 As a Molecular Probe

“…Amidst captivating photophysical properties and facile synthetic and processing requirements, perovskite NCs have an additional key feature, which can be regarded as high reactivity or instability, depending on the ultimate goal . Their structure is sensitive to its environment, rapidly destabilizing under conditions that include the presence of air and water, irradiation, and high temperatures.…”