Highly Emissive and Stable Ge(II)- and Sn(II)-Based Vacancy-Ordered Iodide Double Perovskites.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Photophysics

Background:

• Lead-free self-trapped exciton (STE) emitters are crucial for sustainable optoelectronics.
• Vacancy-ordered double perovskites (VODPs) show potential but stable iodide VODPs with ns² metals are scarce.

Purpose of the Study:

• To develop novel, stable, and efficient lead-free iodide VODPs incorporating ns² metals.
• To investigate the structure-photophysics relationships governing STE emission in these materials.

Main Methods:

• Synthesis of VODPs using N-alkylated 1,4-diazabicyclo[2.2.2]octane (dabco) cations with Ge(II) or Sn(II).
• Characterization of crystal structures and photoluminescence properties (PLQY).
• Correlation analysis between structural parameters and photophysical performance.

Main Results:

• Developed six iodide VODPs with formula (Rdabco)₂B□I₆ (B=Ge(II), Sn(II)), demonstrating tunable steric hindrance and lattice strain.
• Achieved bright room-temperature STE emission with high PLQYs up to 35.0% (Ge) and 36.8% (Sn).
• Observed superior ambient stability (up to two months) compared to 3D perovskite analogs.

Conclusions:

• N-alkylated dabco cations enable the creation of stable and efficient lead-free VODP materials.
• Ge and Sn VODPs exhibit distinct structure-property relationships influencing their luminescence efficiency.
• These VODPs represent a significant advancement in lead-free STE emitters for optoelectronic applications.