Mechanochemical Synthesis, Optical and Magnetic Properties of Pb-Free Ruddlesden–Popper-Type Layered Rb₂CuCl₂Br₂ Perovskite

Abstract

2D layered Ruddlesden–Popper (RP) perovskites gained significant attention owing to their unique optoelectronic properties and ultralow thermal conductivity; however, in comparison to the hybrid Pb-based RP phases, their Pb-free all-inorganic analogues are rarely explored. Herein, we demonstrate the optical and magnetic properties of Pb-free RP-type layered Rb2CuCl2Br2, which was synthesized by liquid-assisted mechanochemistry at ambient temperature and pressure. The dark brown colored material displayed band gap of ∼1.88 eV accompanied by a room-temperature band-edge photoluminescence (PL) at ∼1.97 eV. Moreover, Raman scattering at low-frequency region from the [CuCl4Br2]4– unit and reasonable thermal and environmental stability were manifested. The Rb2CuCl2Br2 exhibited an excitonic absorption which is characteristic of layered perovskites accompanied by a high exciton binding energy. Large Stokes-shifted PL emission, negligible self-absorption, and fast charge carrier lifetimes were evidenced for Rb2CuCl2Br2. Low-temperature (77 K) measurement revealed red-shifted and intense dual emission in contrast to the room-temperature emission. Finally, the temperature-dependent magnetization measurement indicates a paramagnetic to antiferromagnetic (AFM) transition at ∼16.1 K in Rb2CuCl2Br2, primarily related to the interlayer AFM exchange interaction. Competition between the interlayer AFM interaction and the intralayer ferromagnetic interaction determine the nature of magnetic ground state in Rb2CuCl2Br2.

Cyan Emission in Two-Dimensional Colloidal Cs2CdCl4:Sb3+Ruddlesden–Popper Phase Nanoplatelets

“…As demonstrated by the formation of bulk RP phases, this range of compositions creates ample room to adjust chemical properties and tune optoelectronic characteristics . BA 2 MA n –1 Pb n I 3 n +1 (BA = butylammonium) was, for example, used in solar cells attaining a power conversion efficiency of 16.4%, while Rb 2 CuCl 2 Br 2 was found to exhibit an antiferromagnetic behavior promising in spintronic applications . Cs 2 CdCl 4 was explored as an X-ray scintillator material that can be made luminescent through Sb 3+ or Tl + doping .…”

Slowing down the heat in thermoelectrics

“…In fact, atomic bonding in most materials is anharmonic with various strengths of anharmonicity 48–55 . Strong anharmonicity causes intrinsic phonon scattering due to Umklapp processes (U‐processes) and determines the intrinsically low κ lat in materials with multidimensional crystal structures 28,29,34,51,56–62 …”

Pressure‐Induced Phase Transition, Jahn‐Teller Suppression, Optical and Electronic Property Evolutions in Ruddlesden‐Popper Perovskites Rb2CuCl4‐xBrx

“…Powder samples of Rb 2 CuCl 4-x Br x with high purity were synthesized by direct solid-state reactions. [21,24] At ambient conditions, Rb 2 CuCl 4-x Br x (x = 1, 2) adopt the K 2 NiF 4 -type RP perovskite structure (the n = 1 endmember within A n + 1 B n X 3n + 1 RP phases), [38] as shown in Figure 1. The crystal structure of Rb 2 CuCl 2 Br 2 comprises of corner-sharing [CuCl 4 Br 2 ] layers in the bc plane, which are separated by Rb + cations with [Rb-Br] arrays in a rock-salt arrangement.…”

“…Rb 2 CuCl 2 Br 2 was previously reported to exhibit red photoluminescence (PL) around 630 nm under green light irradiation. [24] However, no obvious PL phenomenon was observed in as-synthesized Rb It is interesting to discuss the relationship between crystal structure (pressure-induced Jahn-Teller suppression) and physical properties (bandgap, resistance and photocurrent) of RP perovskites Rb 2 CuCl 4-x Br x under HP. Firstly, it is consistent with previous reports that pressure can greatly suppress Jahn-Teller distortion and may introduce dramatic structural phase transition.…”

“…[21][22][23] Recently, Kundu et al reported the successful mechanochemical synthesis of RP-type Rb 2 CuCl 2 Br 2 perovskite with reasonable thermal and environmental stability. [24] Large Stokes-shifted photoluminescence (PL) togeth-er with negligible self-absorption and fast charge carrier lifetimes were manifested.…”