Understanding perovskite nanocrystal growth and halide segregation using in situ spectroscopies

In this work, we use in situ absorbance and photoluminescence (PL) measurements to study how the polarity of the surface of a reaction vessel alters the nucleation and growth of MAPbBr₃ nanocrystals synthesized in a nonpolar solvent. By comparing syntheses performed in polar glass vials and nonpolar Teflon vials, we find that throughout the duration of a synthesis, reactions performed in glass have higher optical density, while PL peak positions and intensities remain relatively similar. This suggests that the availability of polar glass surfaces increases nanocrystal population through heterogeneous nucleation but does not alter the nanocrystal size. By varying the surface area available to the synthesis using 2 mm glass or Teflon beads, we show that only glass beads cause an increase in optical density, further confirming the role that surface polarity plays in the reaction. This work gives insight into how the surface chemistry of the reaction vessel can help in the understanding of heterogenous nucleation and perovskite nanocrystal growth.