Modulating Self-Trapped Exciton Emission via Structural Phase Transitions in Lead-Free Double Perovskites

Area of Science:

• Materials Science
• Solid-State Chemistry
• Photophysics

Background:

• Metal halide perovskites are crucial for optoelectronic devices.
• Understanding their phase transitions and luminescence is key to material design.
• Lead-free perovskites offer a safer alternative for advanced applications.

Purpose of the Study:

• To synthesize and characterize lead-free double perovskites with tunable optical properties.
• To elucidate the relationship between synthesis conditions, crystal structure, and luminescence.
• To demonstrate the potential of these materials in white-light-emitting diodes (WLEDs).

Main Methods:

• Synthesis of Cs2NaInCl6 and Cs3.4Na0.6InCl7 via controlled solvent (N,N-Dimethylformamide) concentration.
• Experimental analysis including optical property measurements.
• Density Functional Theory (DFT) calculations to understand emission mechanisms.
• Fabrication of WLEDs using synthesized phosphors.

Main Results:

• Phase transition control achieved by varying N,N-Dimethylformamide concentration.
• Sb3+-doped perovskites exhibited high photoluminescence quantum yields (PLQY): 90.3% for blue-emitting Cs2NaInCl6 and 90.1% for yellow-green-emitting Cs3.4Na0.6InCl7.
• Orange-emitting Cs2InCl5·H2O:Sb3+ synthesized by incorporating water.
• Fabricated WLEDs achieved a high color rendering index (Ra) of 92.2 and a correlated color temperature (CCT) of 5119 K.

Conclusions:

• Crystal structure engineering is an effective strategy for tuning halide perovskite optical properties.
• Controlled synthesis enables precise manipulation of phase transitions and luminescence.
• These lead-free perovskites show significant promise for high-performance WLED applications.