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

Abstract

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)2SnI4−xClx 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.

Structure, Morphology, and Photovoltaic Implications of Halide Alloying in Lead‐Free Cs3Sb2ClxI9–x 2D‐Layered Perovskites

“…Of note, the chloride contents in the thin films are smaller compared with the respective chloride contents in precursor solutions, which implies most of the Cl ions leave the film during the fabrication process, likely during the SbI 3 vapor anneal step, consistent with other reports. [2,29] Nonetheless, each subsequent increase in SbCl 3 in the precursor solution ultimately contributed to an increase in final chloride ion content across the entire series. From here on, we will refer to the x values measured by EDXS rather than the theoretical value.…”

“…Lead‐based perovskites have benefitted immensely from compositionally tuning away from methylammonium lead iodide (MAPbI 3 ), giving rise to record‐breaking power conversion efficiencies (PCEs), impressive device stabilities, and broadly tunable optoelectronic properties suitable for a vast range of useful applications. [ 1–8 ] However, there is currently significant motivation to pursue lead‐free perovskite derivatives for a number of reasons that extend beyond the manufacturing and environmental concerns associated with Pb. [ 9–11 ] Group 15 metals, such as arsenic, bismuth, and antimony, have shown promise as alternates to Pb outside of Group 14.…”

Low‐Dimensional Hybrid Perovskites for Field‐Effect Transistors with Improved Stability: Progress and Challenges

“…Particularly, the Cl element can be successfully incorporated into the low-dimensional perovskite crystal lattice to improve the sample morphology and carrier transport mobility; while the process cannot be achieved in the conventional 3D perovskites. [118] Figure 12. Schematics of a) lateral and b) vertical devices for in-plane and out-of-plane carrier transport, respectively.…”

Two‐Dimensional Metal‐Halide Perovskite‐based Optoelectronics: Synthesis, Structure, Properties and Applications

“…In this case, Sn‐based 2D perovskites have been identified as suitable alternatives, while they are still hindered by the instability in the air environment. [ 50 ] Loh et al [ 51 ] reported a Sn‐based hybrid organic–inorganic 2D perovskite of (FSA) 2 SnI 4 with enhanced air stability, using 2‐(4‐(3‐fluoro)stilbenyl)ethanammonium (FSA + ) as the organic cations. The water instability of (FSA) 2 SnI 4 perovskite is ascribed to the water resistance of fluorinated organic chains, as a concrete effect of strongly cohesive bonding contained the H bonding, CH‐X type of H bonding, weak interlayer of F‐F interactions, and weak aspectant type of π‐π interaction.…”