All-Inorganic Metal Halide Perovskite Nanocrystals: Opportunities and Challenges

Abstract

The past decade has witnessed the growing interest in metal halide perovskites as driven by their promising applications in diverse fields. The low intrinsic stability of the early developed organic versions has however hampered their widespread applications. Very recently, all-inorganic perovskite nanocrystals have emerged as a new class of materials that hold great promise for the practical applications in solar cells, photodetectors, light-emitting diodes, and lasers, among others. In this Outlook, we first discuss the recent developments in the preparation, properties, and applications of all-inorganic metal halide perovskite nanocrystals, with a particular focus on CsPbX₃, and then provide our view of current challenges and future directions in this emerging area. Our goal is to introduce the current status of this type of new materials to researchers from different areas and motivate them to explore all the potentials.

Figure 1

Schematic illustration of the methods for the synthesis of colloidal perovskite nanocrystals: (a) hot-injection method, (b) supersaturated recrystallization method, (c) ultrasonication-assisted method, (d) solvothermal method, and (e) microwave-assisted method. The images were modified with permission from refs (a) (14), (b), (18), (c) (19), (d) (21), and (e) (22).

Figure 2

(a) Schematic illustration of the anion-exchange process within the cubic CsPbCl₃ NCs. (b) The XRD patterns indicate similar crystallite size before and after anion exchange. (c) Bright emission covering the entire visible spectral region can be realized with the anion-exchange approach. Images were modified with permission from ref (47). (d) Schematic illustration of partial replacement of Pb²⁺ with divalent cations. Images were modified with permission from ref (49). (e) Digital image and (f) PL spectra showing bright yellow emission of Mn²⁺-doped CsPbCl₃ nanocrystals. Images were modified with permission from ref (51). (g, h) PLQY of CsPbBr₃ can be improved to near 100% by postsynthetic surface treatment using thiocyanate. Images were modified with permission from ref (53).

Figure 3

(a) Schematic illustration and (b) SEM image of the cross-section of a solar cell device. (c) NREL-certified J–V characteristics from forward bias to reverse bias. (d) NREL-certified stabilized current at a constant voltage of 0.95 V. Images were modified with permission from ref (56). (e) Schematic illustration and (f) cross-sectional TEM image of an LED device. Images were modified with permission from ref (27). (g) Schematic illustration of the first CsPbI₃ NCs photodetector. Images were modified with permission from ref (61).

Figure 4

(a) Schematic structure of OPA-capped CsPbBr₃ NCs. (b) J–V–L curve of devices based on different ligands (blue line for OA/OLA-capped CsPbBr₃ NCs, and red line for OPA-capped CsPbBr₃ NCs). Images were modified with permission from ref (68). (c) Schematic structure of CsPbBr₃ NCs capped by long-chain zwitterionic molecules. Images were modified with permission from ref (70).

Figure 5

(a) TEM images of CsPbBr₃ NCs-silica/alumina monolith (SAM). Photostability of the CsPbBr₃ QDs-SAM powder (b) under illumination with a 470 nm LED light and (c) sealed with PDMS on the LED chip (5 mA, 2.7 V). The images were modified with permission from ref (81). (d) TEM image of the obtained CsPbBr₃/SiO₂ Janus NCs. (e) HRTEM image of a single CsPbBr₃/SiO₂ NC. (f) HAADF-STEM image and elemental mapping images. (g) Photographs of (I) CsPbBr₃/SiO₂ NCs, (II) WT-CsPbBr₃ NCs, and (III) HI-CsPbBr₃ NCs thin film stored in humid air (40 °C and humidity of 75%). The images were modified with permission from ref (82).

Figure 6

Schematic illustration of the design of sandwich-like structures with possible shell materials and promising applications.

Figure 7

(a) Cs₃Bi₂Br₉ unit cell, XRD patterns of Cs₃Bi₂Br₉ NCs, and TEM image of Cs₃Bi₂Br₉ NCs. (b) Photographs of as-obtained colloidal Cs₃Bi₂X₉ and XRD patterns of NCs containing pure and mixed halides. (c) Steady-state absorption and PL spectra of NCs containing pure and mixed halides. The images were modified with permission from ref (88). (d) Structure of Cs₂AgBiBr₆. (e) TEM image of Cs₂AgBiCl₆ NCs. (f) TEM image of Cs₂AgBiBr₆ NCs. The images were modified with permission from ref (93).

Figure 8

(a) Schematic illustration of CO₂ photoreduction over the CsPbBr₃ QD/GO photocatalyst. (b) Catalytic performance of CsPbBr₃ QD and CsPbBr₃ QD/GO. The images were modified with permission from ref (95). (c) Catalytic performance of Cs₂AgBiBr₆ NCs in CO₂ reduction. (d) Schematic illustration of the photoreduction of CO₂ over Cs₂AgBiBr₆ NCs. The images were modified with permission from ref (92).