High-quality bulk hybrid perovskite single crystals within minutes by inverse temperature crystallization

Abstract

Single crystals of methylammonium lead trihalide perovskites (MAPbX3; MA = CH3NH3(+), X = Br(-) or I(-)) have shown remarkably low trap density and charge transport properties; however, growth of such high-quality semiconductors is a time-consuming process. Here we present a rapid crystal growth process to obtain MAPbX3 single crystals, an order of magnitude faster than previous reports. The process is based on our observation of the substantial decrease of MAPbX3 solubility, in certain solvents, at elevated temperatures. The crystals can be both size- and shape-controlled by manipulating the different crystallization parameters. Despite the rapidity of the method, the grown crystals exhibit transport properties and trap densities comparable to the highest quality MAPbX3 reported to date. The phenomenon of inverse or retrograde solubility and its correlated inverse temperature crystallization strategy present a major step forward for advancing the field on perovskite crystallization.

Figure 1. Crystal growth process and powder X-ray diffraction.

(a) Schematic representation of the ITC apparatus in which the crystallization vial is immersed within a heating bath. The solution is heated from room temperature and kept at an elevated temperature (80 °C for MAPbBr₃ and 110 °C for MAPbI₃) to initiate the crystallization. (b,c) MAPbI₃ and MAPbBr₃ crystal growth at different time intervals. (d,e) Powder X-ray diffraction of ground MAPbBr₃ and MAPbI₃ crystals. Insets: pictures of the corresponding crystals grown within a non-constraining vessel geometry.

Figure 2. Continuous growth and crystal shape control.

(a) Continuous growth of an MAPbBr₃ crystal by moving the crystal into a larger vial with a fresh growth solution. (b) Shape-controlled crystals of MAPbBr₃ (orange) and MAPbI₃ (black) by varying the geometry of the confining vessel. From left to right—crystals grown in a round-bottom test tube and a 2-mm cuvette.

Figure 3. Steady-state absorption and photoluminescence.

(a) MAPbBr₃ single crystal. (b) MAPbI₃ single crystal. Insets: corresponding Tauc plots displaying the extrapolated optical band gaps.

Figure 4. Carrier lifetime measurements and I–V traces.

(a,b) Transient absorption of (a) MAPbBr₃ and (b) MAPbI₃ crystals. (c,d) I–V of perovskite crystals exhibiting different regions obtained from the log I versus log V plots. The regions are marked for Ohmic (IαVⁿ⁼¹), TFL (IαV^n>3) and Child's regime (IαVⁿ⁼²). The trap densities were calculated from the Child's regime shown in (c,d).