Uniaxial plasmon coupling through longitudinal self-assembly of gold nanorods

Lead-free halide double perovskites offer an environmentallyfriendly alternative to lead halide perovskites for designing optoelectronic solarcell devices. One simple approach to synthesize such double halide perovskites isthrough metal ion exchange. CsPbBr3nanocrystals undergo exchange of Pb2+withAu(I)/Au(III) to form double perovskite Cs2Au2Br6. When excited, a majority ofthe charge carriers undergo quick recombination in contrast to long-lived chargecarries of excited CsPbBr3nanocrystals. This metal ion exchange process isreversible as one can regenerate CsPbBr3by adding excess PbBr2to thesuspension. Interestingly, when subjected to visible light irradiation, Cs2Au2Br6nanocrystals eject reduced Au from the lattice asevidenced from the formation of larger gold nanoparticles. The presence of residual Pb2+ions in the suspension restores the originalCsPbBr3composition. The results presented here provide insight into the dynamic nature of Au within the perovskite lattice underboth chemical and light stimuli.