Halide Perovskite Crystallization Processes and Methods in Nanocrystals, Single Crystals, and Thin Films

Abstract

Halide perovskite semiconductors with extraordinary optoelectronic properties have been fascinatedly studied. Halide perovskite nanocrystals, single crystals, and thin films have been prepared for various fields, such as light emission, light detection, and light harvesting. High‐performance devices rely on high crystal quality determined by the nucleation and crystal growth process. Here, the fundamental understanding of the crystallization process driven by supersaturation of the solution is discussed and the methods for halide perovskite crystals are summarized. Supersaturation determines the proportion and the average Gibbs free energy changes for surface and volume molecular units involved in the spontaneous aggregation, which could be stable in the solution and induce homogeneous nucleation only when the solution exceeds a required minimum critical concentration (Cmin). Crystal growth and heterogeneous nucleation are thermodynamically easier than homogeneous nucleation due to the existent surfaces. Nanocrystals are mainly prepared via the nucleation‐dominated process by rapidly increasing the concentration over Cmin, single crystals are mainly prepared via the growth‐dominated process by keeping the concentration between solubility and Cmin, while thin films are mainly prepared by compromising the nucleation and growth processes to ensure compactness and grain sizes. Typical strategies for preparing these three forms of halide perovskites are also reviewed.

Shape‐Controlled Solution‐Epitaxial Perovskite Micro‐Crystal Lasers Rivaling Vapor Deposited Ones

“…On the other hand, for metal-halide perovskites, solution processing offers facile and low-cost ways to fabricate optoelectronic devices (solar cells, [7] photodetectors, [8] light emitting diodes, and lasers [9][10][11] ) mostly in polycrystalline form, [12,13] but also in the form of macroscopic, [14][15][16] micrometer sized or nanocrystalline single crystals. [17][18][19][20][21][22][23][24][25][26][27] Due to the outstanding results from solution processed metal-halide perovskites, we consider them also to be as attractive candidates for epitaxial growth from solutions, providing obvious advantages in comparison to vapor phase epitaxy: almost no costs for growth equipment, energy efficiency due to low temperature processing, and simple applicability also to organic-inorganic hybrid perovskites. In vapor phase epitaxy, the hybrid perovskites cause severe problems, because their decomposition during evaporation unavoidably provides hydrogen-halide acids, [28] which are strongly corrosive and ruin the used vacuum-chamber and pump systems.…”

Self‐Assembly of 2D Hybrid Double Perovskites on 3D Cs2AgBiBr6 Crystals towards Ultrasensitive Detection of Weak Polarized Light

“…In our case, we used HBr aqueous solution to grow the HCs because it can simultaneously provide Branions and serve as the solvent. [26] The cation sources including BLA + , Cs 2 CO 3 , Ag 2 O, and Bi 2 O 3 , were easily dissolved in HBr aqueous solution at high temperature (see the Experimental Section in the Supporting Information for more details); and the solubility curves of the resulting (BLA) 2 CsAgBiBr 7 and Cs 2 AgBiBr 6 in HBr solution are displayed in Figure S1a. At the initial stage of reaction, the solvent evaporation triggers the crystallization of 3D double perovskite Cs 2 AgBiBr 6 owing to the fact that its solubility is much lower than that of the 2D (BLA) 2 CsAgBiBr 7 (Figure 1a (1)).…”

“…High‐quality (BLA) 2 CsAgBiBr 7 /Cs 2 AgBiBr 6 heterocrystals (HCs) were obtained by self‐assembling 2D (BLA) 2 CsAgBiBr 7 single crystals atop the 3D Cs 2 AgBiBr 6 single crystals as shown in Figure 1a. In our case, we used HBr aqueous solution to grow the HCs because it can simultaneously provide Br ‐ anions and serve as the solvent [26] . The cation sources including BLA + , Cs 2 CO 3 , Ag 2 O, and Bi 2 O 3 , were easily dissolved in HBr aqueous solution at high temperature (see the Experimental Section in the Supporting Information for more details); and the solubility curves of the resulting (BLA) 2 CsAgBiBr 7 and Cs 2 AgBiBr 6 in HBr solution are displayed in Figure S1a.…”

Lead-free all-inorganic halide double perovskite materials for optoelectronic applications: progress, performance and design

“…They can be prepared by balancing different thermodynamic processes, such as crystal growth, homogeneous and heterogeneous nucleation. 35,125 For instance, the minimum critical concentration should be rapidly increased in the nucleation-dominated process for the synthesis of nanocrystals. In contrast, the concentration should be maintained between solubility and minimum critical concentration through a growth-dominated process to synthesize single crystals.…”