Phase Transition and Luminescent Property Change Induced by Different Organic Cations in One-Dimensional Double Perovskites

Abstract

Double perovskites (DPs) have attracted attention in the field of luminescence due to their inherent broadband emission of self-trapping excitons. In this work, we choose [(CH 3 ) 3 NCH 2 CHCH 2 ] + and [CH 3 CHOHCH 2 NH 2 ] + as organic cations to synthesize two new organic−inorganic hybrid DPs, [(CH 3 ) 3 NCH 2 CHCH 2 ] 2 KInCl 6 (1) and [CH 3 CHOHCH 2 NH 2 ] 2 KInCl 6 (2).The [KCl 6 ] 3− and [InCl 6 ] 3− octahedra are interchangeably connected by sharing two opposite faces, forming a one-dimensional coordination chain. Each K atom coordinates with six chlorine atoms in 1, while it coordinates with two oxygen atoms in addition to the six chlorine atoms in 2. The coordination between ions K and O in compound 2 may have significantly reduced its luminescence. As a result, compound 1 shows bright-yellow light with a quantum yield of more than 90%, while 2 shows weak blue light with a quantum yield of only 0.98%. In addition, different from no phase transition found in 2, 1 undergoes a reversible phase transition at 324/307 K in the heating−cooling cycle. Through structural and spectral analysis and density functional theory calculation, we conclude that the larger degree of [InCl 6 ] 3− octahedral distortion and the larger anion distance (In•••In) also cause the PLQY of compound 1 to be higher than that of compound 2.

Second-Order Nonlinear Switching and Photoluminescence Properties of Cd-Based Hybrid Perovskite with High-Temperature Phase Transition

“…Under the strongest excitation at 277 nm, a pronounced emission peak is observed at 410 nm with a full width at half-maximum (fwhm) of 80 nm. Combined with the previous studies on the optical properties of hybrid perovskites, − the large Stokes shift of 133 nm and broad emission of (4-methoxypiperidinium)CdCl 3 may be associated with the structural distortion of the inorganic framework. The extent of the CdCl 6 octahedral distortion was quantitatively evaluated using the octahedral bond length distortion (Δ d ) and bond angle variance (σ 2 ) parameters, calculated by the following two equations: normalΔ d = 1 6 ∑ i = 1 6 true[ d i − d 0 d 0 true] 2 σ 2 = 1 11 falsefalse ∑ i = 1 12 false( θ i − 90 ) 2 where d i represents the individual Cd–Cl bond lengths, d 0 is the average Cd–Cl bond length, and θ i represents the individual Cl–Cd–Cl bond angles of the CdCl 6 octahedron in the structure at LTP.…”