In/Bi-based Direct- and Indirect-Gap Hybrid Double-Perovskite-Derived 1D Halides with Near-Unity Quantum Yield via Sb³⁺ Doping

The hybrid halide double-perovskite family is a highly diverse system that allows a wide range of property tunings via structural variations. Using organic components instead of small A-site cations to reduce the dimensionality of the structure and doping metal cations can modulate their structure and improve the optoelectronic performance. Here, by introducing an organic cationic ligand morpholine (Mor), we report on a new family of double-perovskite-derived halides (Mor)₂ABX₆ (A = Na, K; B = In, Bi; X = Cl, Br) with several unique types of one-dimensional (1D) structures constituted by [AX₄O₂] and [BX₆] octahedron units. These materials are nonemissive at room temperature, while with an Sb³⁺-doping strategy, the photoluminescence can be drastically enhanced. For (Mor)₂KInX₆, their quantum efficiencies are improved to near unity via Sb³⁺ doping. Meanwhile, for (Mor)₂KBiX₆, the photoluminescence improvement from Sb³⁺ doping is negligible. With density functional theory calculations, (Mor)₂KInBr₆ and (Mor)₂KBiBr₆ have been identified to have direct- and indirect- band gap, respectively. This work expands a new material space for organic-inorganic hybrid double-perovskite-derived materials and provides insights into tuning their optical properties.