Stability of Sn based inorganic perovskite quantum dots

Abstract

Metal halide perovskite crystal structures have emerged as a class of optoelectronic materials, which combine the ease of solution processability with excellent optical absorption and emission qualities. However, the most promising perovskite structures rely on lead as a cationic species, thereby hindering commercial application. The replacement of lead with non-toxic alternatives such as tin has been studied in bulk but not in nanocrystals. In this work, we synthesize Sn and Pb based alloy perovskite nanocrystals by direct synthesis method, taking mixture of Pb and Sn precursors in the desired ratio leading to quantum dots (QDs) of CsPb1-xSnxBryI3-y with successful Sn incorporation into the host lattice. As colloidal stability of these QDs is a crucial factor for device applications, we have studied the stability of the QDs under different conditions for these Sn based QDs and have found them to degrade faster upon using anti-solvents during washing process. In order to stabilize them, we have devised a purification method that is also discussed. Further, even though the optical and crystal structure stability in some of the inorganic perovskites leaves much room for improvement, so far there have been no studies on the structure property correlation. Here we study their structural purity and their optical stability after understanding the structure property correlation in CsPbI3 and CsPbBr3 perovskite structures. The stability of Sn doped perovskites obtained from a logical understanding of structure property correlation is found to be extremely stable across the series of compounds for upto three months.