Halide exchange and surface modification of metal halide perovskite nanocrystals with alkyltrichlorosilanes

Metal halide perovskite nanocrystals have recently emerged as promising materials for light emitting displays and lasing applications due to their narrow emission wavelengths, high photoluminescence quantum yields, and readily adjustable emission wavelengths. For these metal halide perovskite nanocrystals to be useful in commercial applications, their stability must be increased and the photoluminescence quantum yields of the iodide (red emitting) and chloride (blue emitting) containing derivatives must also be increased. The photoluminescence quantum yields of blue emitting CsPbCl₃ nanoparticles lag behind those of green emitting CsPbBr₃ nanoparticles, with maximum photoluminescence quantum yields of 1-10% previously reported for CsPbCl₃ as compared to 80-100% for CsPbBr₃. Herein, we show that alkyltrichlorosilanes (R-SiCl₃) can be used as Cl-sources for rapid anion exchange with host CsPbBr₃ nanocrystals. This anion exchange reaction is advantageous in that it can be performed at room temperature and results in highly dispersible nanoparticles coated with siloxane shells. CsPbCl₃ nanoparticles produced through Cl-exchange with R-SiCl₃ show significantly improved long-term stability and high photoluminescence quantum yields of up to 12%. These siloxane coated nanocrystals are even stable in the presence of water, whereas CsPbCl₃ nanoparticles synthesized through other routes rapidly degrade in the presence of water.