Tunable optical and scintillation properties of two-dimensional tin mixed-halide perovskites

Abstract

The controllable doping of hybrid organic–inorganic perovskites (HOIPs) has fueled strong interest in their utilization as scintillating materials. In terms of cation engineering, tin mixed-halide perovskites (TMHPs) are considered a stronger contender than their conventional hybrid perovskite counterparts. However, their inability to undergo physicochemical alteration via simultaneous A-site and X-site substitution remains unresolved to date. In this work, we tailor the organic ligand and halide mixture of TMHPs to shed some light on their optical and scintillation properties. By introducing three organic ligands, we synthesize phenylmethylammonium (PMA), phenethylammonium (PEA) and phenylpropylammonium (PPA) and retain the Br : I ratio at 3 : 1. In terms of structural order, we show that the interlayer spacing between the inorganic layers is gradually extended from 9.88 Å for (PMA)₂SnBr₃I and 10.29 Å (PEA)₂SnBr₃I to 10.06 Å for (PPA)₂SnBr₃I. Based on geometrical order, organic chain penetration and octahedral distortion angles, we propose a rational design to modulate the absorption, photoluminescence (PL), optical bandgap, and thermal quenching of TMHPs. (PMA)₂SnBr₃I exhibits the fastest decay time (τ_avg = 1.1 ns) compared to (PEA)₂SnBr₃I (τ_avg = 2.51 ns) and (PPA)₂SnBr₃I (τ_avg = 3.54 ns), indicating that TMHPs are promising candidates for scintillator applications. This finding is corroborated by density functional theory, which outlines the weakened antibonding interaction between I 5p and Sn 5s orbitals upon tailoring the organic ligand of the perovskite. Our results demonstrate the importance of cation engineering in leveraging innovative hybrid perovskites with novel responses via a rational design.