Preferably Oriented Growth of Methylammonium-Based Perovskite Single Crystals with Ionic Liquid Solvent

Crystalline orientation control is of great importance for the optoelectronic applications of perovskite single crystals due to their structural anisotropy. Herein, we develop an ionic liquid, named methylammonium difluoroacetate (MA2FAc), as a growth solvent to fabricate multifarious methylammonium-based perovskite single crystals. Typically, it can easily achieve preferably oriented growth of high-quality MAPbI₃ single crystals with (002) facet exposition. Benefiting from the superior charge carrier properties along the [001] direction, a bias-modulating broadband/narrowband switchable photodetector is proposed, which exhibits a broadband specific detectivity D* of 1.1 × 10¹¹ Jones under 0.1 V and a narrowband D* of 9.0 × 10⁹ Jones with a full width at half-maximum (fwhm) of 31 at 810 nm merely under 0.25 mV, respectively. Theoretical calculations and experimental analysis reveal that the difluoromethyl substitution can simultaneously regulate solvation characteristics of the acetate anion as well as crystallization kinetics of perovskite single crystals. In light of the universal solvent utilization of MA2FAc, this work provides a new perspective in the solution growth process of high-quality methylammonium based perovskite single crystals.