Lead-Free Small-Bandgap Cs2CuSbCl6 Double Perovskite Nanocrystals

Lead-free halide double perovskites (DPs) have attracted great attention due to their stability, nontoxicity and good photophysical property. In this work, we report a new, small-bandgap Cs 2 CuSbCl 6 DP nanocrystals (NCs) with a bandgap of 1.66 eV, which is the smallest bandgap in reported lead-free three-dimensional DP NCs. Density functional theory calculations confirm that Cs 2 CuSbCl 6 DP has an indirect bandgap of 1.70 eV, in good agreement with the experimental result. The photophysical property of Cs 2 CuSbCl 6 NCs is studied by the combination of femtosecond transient absorption (TA) and nanosecond TA techniques. In addition, the Cs 2 CuSbCl 6 NCs exhibit good stability exposed in the air. These results show that these NCs will have great potential to be used as a light-absorbing material for photovoltaic applications.