Antisolvent-Assisted Growth of Centimeter-Scale CsPbBr$_3$ Perovskite Single Crystals: A Theory-Guided Approach

TL;DR

The paper tackles the challenge of producing large, high‑quality all‑inorganic CsPbBr$_3$ single crystals by integrating a theory‑guided AVC framework. It rationally selects a binary solvent ($9:1$ DMSO/DMF) to balance solubility and kinetics via Gutmann's Donor Number and uses Hansen Solubility Parameters to choose ethanol as the antisolvent, establishing a defined growth window. Through systematic experimentation—varying precursor concentration, pre‑titration to metastability, and selective seeding—the authors identify optimal conditions ($0.35~ ext{M}$ precursor, ethanol as antisolvent, and a pre‑titration step) that yield phase‑pure orthorhombic CsPbBr$_3$ single crystals up to $1$ cm in size within one week at room temperature, with robust thermal stability up to $550^{ frac{ ext{C}}{ ext{C}}}$. Comprehensive XRD, EDX, TGA, and UV–Vis analyses confirm near‑stoichiometric composition, high crystallinity, and a band gap around $2.20$ eV, highlighting the method's potential for scalable, high‑quality perovskite crystals in optoelectronics.

Abstract

The fabrication of large, high-quality single crystals (SCs) of all-inorganic cesium lead bromide (CsPbBr$_3$) via accessible methods remains a significant challenge. This work presents a systematic approach to optimize the antisolvent vapor-assisted crystallization (AVC) method, where the experimental design is guided by a theoretical methods at each step. A synergistic 9:1 (v/v) DMSO/DMF binary solvent was selected to balance solubility and kinetics, a choice rationalized by an analysis of Gutmann's donor numbers. Subsequently, ethanol was selected as a promising antisolvent by evaluating its properties against key criteria of miscibility and diffusion rate using Hansen Solubility Parameters (HSP) and Fick's law expressed in terms of saturated vapor pressure. Within this rationally-defined chemical system, the "growth window" was experimentally mapped, identifying an optimal precursor concentration of 0.35 M and a preliminary titration step to induce a controlled metastable state. The optimized protocol consistently yields phase-pure, orthorhombic CsPbBr$_3$ SCs up to 1 cm in size within one week at room temperature. The resulting crystals exhibit high crystallinity and thermal stability up to \SI{550}{\celsius}

Figures (8)

• Figure 1: Schematic illustration of the experimental procedure for the synthesis of CsPbBr$_3$ SCs. (a) Preparation of the precursor solution from CsBr and PbBr$_2$ powders in a DMSO/DMF solvent mixture. (b) Crystal growth from the as-prepared solution using the AVC method (Group (a)). (c) Pre-treatment of the precursor solution via titration with ethanol and re-filtration to create a metastable state. (d) Crystal growth from the pre-treated solution using the AVC method (Group (b)). (e) Seeded crystal growth from the pre-treated solution using the AVC method (Group (c)).
• Figure 2: Theoretical framework for controlled crystallization. (a) Classical Nucleation Theory (CNT) plot showing the change in Gibbs free energy ($\Delta G$) as a function of nucleus radius ($r$). The energy barrier for nucleation ($\Delta G^*$) at the critical radius ($r_c$) must be overcome for stable growth. (b) The LaMer diagram illustrating the evolution of solute concentration ($C$) over time. Stage I is the induction period, Stage II is the burst nucleation event, and Stage III is the diffusion-limited growth of existing nuclei. Successful growth of high-quality SCs requires maintaining the system within the metastable zone between the saturation concentration ($C_{\text{sat}}$) and the minimum concentration for nucleation ($C_{\text{min}}$).
• Figure 3: Photographs of CsPbBr$_3$ SCs grown from precursor solutions of varying concentrations: (a) 0.2 M, (b) 0.3 M, (c) 0.4 M, and (d) 0.5 M. The solvent used was a 9:1 DMSO/DMF mixture, and the antisolvent was pure ethanol.
• Figure 4: Solubility curve and schematic phase diagram of the CsPbBr$_3$ synthesis derived from experimental solubility data. The zoning interpretation follows the LaMer model. The "Stable Zone" (green) represents the undersaturated solution. The "Growth Window" (pink) corresponds to the metastable region ($C_{sat} < C < C_{min}$), ideal for growth of high-quality SCs. The "Nucleation Zone" (orange) indicates the region of labile supersaturation where spontaneous nucleation occurs. The red point marks the starting condition for the as-prepared solution (Group (a)), which is prone to kinetic overshoot into the nucleation zone (red arrow). The blue point marks the starting condition for the pre-treated solution (Groups (b) and (c)) after titration to $\approx$38% ethanol fraction, positioned at the solubility boundary ($C_{sat}$), allowing for controlled entry into the metastable growth window (blue arrow). The solid black line represents the experimentally determined solubility curve, while the red dashed line shows the best fit using the empirical model presented in the inset. The equation and high R$^2$ = 0.9617 value confirm the model's accuracy.
• Figure 5: Photographs of CsPbBr$_3$ SCs obtained under 18 distinct experimental conditions. Rows (a-c) correspond to different precursor solution treatments: (a) as-prepared solution, (b) solution pre-treated by titration and re-filtration, (c) pre-treated solution with added seed crystals. Columns (1-6) correspond to different antisolvent compositions, with the volume percentage of DMSO in the ethanol/DMSO mixture increasing from 0% in column 1 to 50% in column 6, in 10% increments.