B-Site Columnar-Ordered Halide Double Perovskites: Theoretical Design and Experimental Verification

Area of Science:

• Materials Science
• Solid-State Chemistry
• Optoelectronics

Background:

• Halide double perovskites (A₂B(I)B(III)X₆) are promising for optoelectronics.
• Rock-salt ordering in B-sites limits electronic dimensionality, leading to large bandgaps and carrier masses.

Purpose of the Study:

• To explore novel halide double perovskite structures with modulated electronic properties.
• To investigate the effect of B-site cation arrangement on electronic dimensionality.

Main Methods:

• Density functional theory (DFT) calculations were employed to analyze electronic structures.
• Symmetry analysis guided the proposal of new crystal structures.
• Experimental synthesis and characterization of proposed compounds.

Main Results:

• A new family of halide double perovskites (A₂B(I)B(II)X₅) with columnar-ordered B-site cations was proposed.
• Cs₂AgPdCl₅, Cs₂AgPdBr₅, and Cs₂AgPtCl₅ were successfully synthesized.
• These compounds show small bandgaps (1.33-1.77 eV), suitable for visible light absorption.
• Small carrier effective masses along octahedra chains and good stability were observed.

Conclusions:

• Manipulating B-site cation arrangement effectively modulates electronic properties of halide double perovskites.
• The new columnar-ordered structure provides a platform for developing advanced optoelectronic semiconductors.
• This work expands the scope of halide double perovskites with +1 and +2 oxidation state cations.