The Role of Chloride Incorporation in Lead-Free 2D Perovskite (BA)₂SnI₄: Morphology, Photoluminescence, Phase Transition, and Charge Transport

The incorporation of chloride (Cl) into methylammonium lead iodide (MAPbI₃) perovskites has attracted much attention because of the significantly improved performance of the MAPbI₃-based optoelectronic devices with a negligible small amount of Cl incorporation. It is expected that the Cl incorporation in 2D perovskites with layered nature would be much more efficient and thus can greatly alter the morphology, optical properties, phase transition, and charge transport; however, studies on those aspects in 2D perovskites remain elusive up to date. Here, a one-pot solution method to synthesize the Cl-doped lead-free 2D perovskite (BA)₂SnI₄ with various Cl incorporation concentrations is reported and how the Cl incorporation affects the morphology change, photoluminescence, phase transition, and charge transport is investigated. The Cl element is successfully incorporated into the crystal lattice in the solution-processed perovskite materials, confirmed by X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy measurements. The temperature-dependent photoluminescence studies indicate that the emission properties and phase transition behavior in (BA)₂SnI_{4- x} Cl _x can be tuned by varying the Cl incorporation concentration. Electrical measurement suggests that the charge transport behavior can also be greatly altered by the Cl doping concentration and the electrical conductivity can be significantly improved under a higher Cl incorporation concentration.