Highly efficient emission in lead-free inorganic vacancy-ordered Sb-Bi-alloyed halide quadruple perovskites

Lead-free vacancy-ordered quadruple perovskites have received extensive attention in optoelectronic applications. We study the optical properties and charge-carrier dynamics of Cs 4 Mn(Bi 1-x Sb x ) 2 Cl 12 (0 ≤  x  ≤ 1) quadruple perovskite single crystals (SCs), which exhibit excellent stability and Mn 2+ -based photoluminescence (PL) emission. The ratio of Bi:Sb has a great influence on PL intensity. As the Bi 3+ content increases, the PL quantum yield (PLQY) shows a monotonically increasing trend and enhances by more than 40 times, attributed to larger energy difference between conduction band minimum and 4 T 1 state of Mn 2+ ions, weaker Mn-Mn coupling interaction due to longer Mn···Mn distance and smaller Jahn-Teller distortion, and lower carrier-phonon coupling. Moreover, Cs 4 Mn(Bi 1-x Sb x ) 2 Cl 12 nanocrystals were synthesized through top-down ultrasonic crushing method. The PL quenching of Cs 4 MnBi 2 Cl 12 nanocrystals compared to corresponding SCs arises from surface defect trapping. Our work provides an in-depth understanding of Mn 2+ -based PL mechanism.