Enhanced Charge Carrier Transport in Lead-Free Double-Perovskite Cs2AgBiCl6 Nanocrystals Grown In Situ on Reduced Graphene Oxides

Double perovskites have shown great potential in addressing the toxicity and instability issues of lead halide perovskites toward practical applications. High-quality Cs2AgBiCl6 double-perovskite nanocrystals (NCs) with balanced stoichiometric ratios, excellent morphology, and highly oriented crystallinity with an indirect band gap of 2.35 eV were prepared using the thermal injection method. The Cs2AgBiCl6 NCs have an emission line width of 12-105 nm and a photoluminescence (PL) lifetime of 5.7-20.8 ns. Heterostructures grown in situ are rarely reported compared to common doping with different metal cations or rare-earth elements, such as Sn, Sb, In, TI, Mn, Yb, Er, etc. In an effort to improve the charge separation and transfer following exciton generation in such NCs, novel functional nanocomposites were synthesized by in situ growth of Cs2AgBiCl6 perovskite NCs on two-dimensional graphene nanosheets. The Cs2AgBiCl6 NC and graphene nanosheet composites have significant PL bursts and shorter PL decay lifetimes compared to pure Cs2AgBiCl6 NCs. This suggests that an effective excited-state charge transfer occurs between Cs2AgBiCl6 NCs and graphene nanosheets. This composite material has good potential for applications such as absorber layers for photovoltaic devices and photocatalysts.