Tuning Phase Stability and Band Gap in Vacancy-Ordered Double Perovskites Rb_{(2- x )}Cs_xSnI₆ Through Variations in...

Area of Science:

• Materials Science
• Solid-State Chemistry
• Crystallography

Background:

• A2SnI6 vacancy-ordered double perovskites are gaining attention for their potential applications.
• Their phase instabilities offer a route to tune structural and functional properties.
• Understanding these phase transitions is key to material design.

Purpose of the Study:

• To synthesize Rb2SnI6, Rb1.1Cs0.9SnI6, and Cs2SnI6 using solution methods.
• To investigate the phase transitions of these double perovskites under varying temperatures.
• To explore the effect of A-site cation engineering on their structure and optoelectronic properties.

Main Methods:

• Solution synthesis of targeted A2SnI6 double perovskite compounds.
• Variable temperature powder X-ray diffraction (PXRD) for structural analysis.
• Calorimetric studies to confirm phase transitions.

Main Results:

• A new cubic (Fm-3m) structure was identified for Rb2SnI6 at 320 K.
• Partial Cs+ substitution for Rb+ lowered the cubic phase transition temperature.
• Optical band gaps decreased with increasing A-site cation size, ranging from 1.28-1.33 eV.

Conclusions:

• A-site cation engineering is a viable strategy to control the phase stability and optoelectronic properties of A2SnI6 double perovskites.
• The findings provide insights into the structure-property relationships of these lead-free halide perovskites.
• This work contributes to the development of novel materials for optoelectronic applications.