The Effect of Nonsolvent Post-Processing Induced Structural and Morphological Changes on the Optoelectronic Properties of CsPbBr 3 Nanocrystals

Significant efforts have been devoted to optimizing the postsynthesis processing of all-inorganic colloidal CsPbBr₃ nanocrystals (NCs) to achieve stable and ultrapure green emission. However, these NCs harbor a variety of compositional, structural, and surface defects, which undergo dynamic changes during nonsolvent purification. Despite recent advances, the mechanisms underlying degradation during purification and their effects on the photophysical properties of CsPbBr₃ NCs remain unclear. In this study, we examine how the polarity of nonsolvents influences the structural integrity, packing behavior, defects formation, as well as optical properties of the resultant NCs, i.e., photoluminescence (PL) blinking, and charge-carrier recombination dynamics. Using synchrotron-based in situ small-angle X-ray scattering, we show that ligand-shell removal during purification induces NC aggregation through a hierarchical, turbostratically stacked assembly process. Ex situ grazing-incidence X-ray scattering further reveals the atomic and nanoscale orientational ordering in NC thin films. Transmission electron microscopy demonstrates that ketone-based washing results in rapid, disordered aggregation and planar defect formation, whereas ester-based washing leads to slower aggregation without stacking faults. Moreover, single-particle PL microscopy indicates pronounced blinking in ketone-treated NCs, attributed to nonradiative structural defect formation. Finally, our findings suggest that ketone-processed NCs exhibit poor electroluminescence performance, whereas ester-processed NCs retain structural integrity and achieve external quantum efficiencies of up to ∼17.6% in light-emitting diodes.