PNNL

Abstract

Using complementary experimental measurements and computational predictions of spectroscopic measurements (EXAFS, XANES, and UV-Vis), we have determined the identity of the most stable iodoplumbate species in dilute lead halide perovskite precursor solutions. We have determined which species are most likely to be thermodynamically stable, compared to others that are unstable or, at best, metastable. Condensed phase (b initio) models were constructed of the solution and the resulting ensembles were used to directly compare to the experimental results of the EXAFS, XANES, and UV-vis spectra of PbI2 : MAI in DMF. The results of this study suggest that that only Pb2+, PbI+, and PbI2 are present in dilute lead perovskite precursor solutions as thermodynamically stable entities. Our interpretation of the relative stability of iodoplumbate species in solution, based on an analysis of EXAFS and XANES spectra, provides critically important new insight into the species most likely to be responsible for crystal nucleation and growth in these materials. This insight will have significant consequence on the broad scientific community, which will necessitate the reinterpretation of peaks in the UV-vis spectra of lead halide perovskite precursor solutions.