High-entropy halide perovskite single crystals stabilized by mild chemistry

Area of Science:

• Materials Science
• Solid-State Chemistry
• Semiconductor Physics

Background:

• High-entropy materials (HEMs) show promise for functional applications but typically require high-temperature synthesis (>1000°C) and complex processing.
• Developing low-temperature synthesis routes for HEMs is crucial for broader accessibility and reduced manufacturing costs.
• Designing crystal structures with ionic bonding and low cohesive energies is a key strategy for enabling low-temperature HEM formation.

Purpose of the Study:

• To develop room-temperature (20°C) and low-temperature (80°C) solution-based synthesis methods for high-entropy semiconductor (HES) single crystals.
• To explore the formation of HES single crystals based on the cubic Cs2MCl6 vacancy-ordered double-perovskite structure.
• To investigate the structural and electronic properties arising from the incorporation of multiple metal elements in the M-site.

Main Methods:

• Solution-based synthesis at 20°C and 80°C using multi-element inks containing Cs+ cations and isolated [MCl6]2- anions (M=Zr, Sn, Te, Hf, Re, Os, Ir, Pt).
• Self-assembly of stabilized complexes in hydrochloric acid to form single-phase single crystals.
• Characterization of the crystal structure, stoichiometry, and electronic properties of the resulting HES single crystals.

Main Results:

• Successful synthesis of single-phase, single-crystal high-entropy semiconductors with the Cs2MCl6 double-perovskite structure at low temperatures.
• Formation of two families of HES: five-element and six-element compositions occupying the M-site as a random alloy in near-equimolar ratios.
• Observation of complex vibrational and electronic structures due to disordered [MCl6]2- octahedral molecular orbitals and exciton interactions.

Conclusions:

• A novel, low-temperature solution synthesis route for high-entropy semiconductor single crystals has been established.
• The developed metal halide perovskite HES single crystals exhibit unique structural and electronic properties driven by high entropy.
• This work opens new avenues for designing and fabricating advanced functional materials under milder conditions.