Fuqian Yang1
University of Kentucky1
We have developed a green-route approach to prepare lead-free double perovskite Cs<sub>2</sub>SnI<sub>6</sub> powder and nanocrystals, using an environmentally friendly aqueous solution. The sonication of the Cs<sub>2</sub>SnI<sub>6</sub> powder in hexane under ambient conditions leads to the formation of Cs<sub>2</sub>SnI<sub>6</sub> nanocrystals. The Cs<sub>2</sub>SnI<sub>6</sub> powder and nanocrystals exhibit band gaps of 1.3 and 2.8 eV, respectively. There is a difference of 1.5 eV in the band gaps. The Cs<sub>2</sub>SnI<sub>6</sub> nanocrystals with good long-term structural and optical stabilities have a PLQY of ~7% and a PL peak wavelength of 440 nm over a span of 50 days. The dual-color emission of the perovskite Cs<sub>2</sub>SnI<sub>6</sub> is likely due to the dependence of dielectric constant on crystal size instead of the effect of quantum confinement. This work is supported by the NSF through the grant CMMI-1854554 and CBET- 2018411.