Capping ligands controlled structural and optoelectronic properties of CsPbBr3 nanocrystals

The relative amount of capping ligands plays an integral role in stability of CsPbBr3 perovskite nanocrystal. The hot-injection approach is implemented for synthesis of CsPbBr3 nanocrystals by changing the concentrations of Oleic acid:Oleylamine. Lower oleic acid concentration with respect to oleylamine concentration resulted in formation of orthorhombic CsPbBr3, along with slight blue shift in absorbance spectra with better size control of nanocrystals. However, the higher oleic acid concentration with respect to oleylamine lead to formation of tetragonal CsPb2Br5, red shift in absorbance spectra, aggregation of perovskite nanocrystals. The concentration ratio of 0.4:0.6 of capping ligands i.e., oleic acid to oleylamine is found to be the optimized for attaining stable CsPbBr3 perovskite nanocrystals, rendering improved photoresponse of CsPbBr3 perovskite nanocrystals film. The photocurrent density of CsPbBr3 perovskite nanocrystals film with oleic acid to oleylamine ratio of 0.4:0.6 is observed to be similar to 1.9 x 10(-9) A/cm(2) at 1 V bias. The investigations confirm that by tuning the concentration of capping ligands the structural, optoelectronics properties of CsPbBr3 perovskite nanocrystals can be effectively controlled as per the application.