Controlled Synthesis of Lead-Free and Stable Perovskite Derivative Cs₂SnI₆ Nanocrystals via a Facile Hot-Injection Process

Colloidal nanocrystals of lead halide perovskites have recently received great attention due to their remarkable performance in optoelectronic applications (e.g., light-emitting devices, flexible electronics, and photodetectors). However, the use of lead remains of great concern due to its toxicity and bioaccumulation in the ecosystem; herein we report a strategy to address this issue by using tetravalent tin (Sn4+) instead of divalent lead (Pb2+) to synthesize stable Cs2SnI6 perovskite nanocrystals. The shapes of as-synthesized Cs2SnI6 nanocrystals are tuned from spherical quantum dots, nanorods, nanowires, and nanobelts to nanoplatelets via a facile hot-injection process using inexpensive and nontoxic commercial precursors. Spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM) and simulation studies revealed a well-defined face-centered-cubic (fcc) perovskite derivative structure of Cs2SnI6 nanocrystals. The solution-processed Cs2SnI6 nanocrystal-based field effect transistors (FETs) displayed a p-type semiconductor behavior with high hole mobility (>20 cm2/(V s)) and high I-ON/I-OFF ratio (>104) under ambient conditions. We envision that this work will pave the way to produce new families of high-performance, stable, low-cost and nontoxic nanocrystals for optoelectronic applications.