Exploring Nanoscale Structure in Perovskite Precursor Solutions Using Neutron and Light Scattering

Tailoring the solution chemistry of metal halide perovskites requires a detailed understanding of precursor aggregation and coordination. In this work, we use various scattering techniques, including dynamic light scattering (DLS), small angle neutron scattering (SANS), and spin-echo SANS (SESANS) to probe the nanostructures from 1 nm to 10 mu m within two different lead-halide perovskite solution inks (MAPbI(3) and a triplecation mixed-halide perovskite). We find that DLS can misrepresent the size distribution of the colloidal dispersion and use SANS/SESANS to confirm that these perovskite solutions are mostly comprised of 1-2 nm-sized particles. We further conclude that if there are larger colloids present, their concentration must be <0.005% of the total dispersion volume. With SANS, we apply a simple fitting model for two component microemulsions (Teubner-Strey), demonstrating this as a potential method to investigate the structure, chemical composition, and colloidal stability of perovskite solutions, and we here show that MAPbI(3) solutions age more drastically than triple cation solutions.

Automated summary

Tailoring the solution chemistry of metal halide perovskites requires understanding precursor aggregation and coordination. In this study, various scattering techniques were used to investigate the nanostructures in two different lead-halide perovskite solution inks. It was found that DLS can misrepresent the size distribution of the colloidal dispersion, while SANS/SESANS confirmed that these solutions mainly consist of 1-2 nm-sized particles.