Optical Fingerprints of Polynuclear Complexes in Lead-Halide Perovskite Precursor Solutions

TL;DR

This study combines theoretical and experimental approaches to identify optical signatures of polynuclear lead-iodide complexes in precursor solutions, emphasizing their importance in understanding solution chemistry for lead-halide perovskite fabrication.

Contribution

It provides the first combined ab initio and experimental evidence of specific polynuclear complexes in lead-iodide solutions, clarifying their spectral fingerprints.

Findings

Optical spectra of specific iodoplumbate complexes match high-concentration solutions.

Polynuclear complexes significantly influence the optical properties of precursor solutions.

Understanding these complexes aids in better interpretation of solution chemistry for perovskite synthesis.

Abstract

Solvent-solute interactions in precursor solutions of lead halide perovskites (LHP) critically impact the quality of solution-processed materials, as they lead to the formation of a variety of poly-iodoplumbates that act as building blocks for LHP. The formation of [PbI$_{2+n}$]$^{n-}$ complexes is often expected in diluted solutions while coordination occurring at high concentrations is not well understood yet. In a combined \textit{ab initio} and experimental work, we demonstrate that the optical spectra of the quasi-one-dimensional iodoplumbate complexes PbI$_2$(DMSO)$_4$, Pb$_2$I$_4$(DMSO)$_6$, and Pb$_3$I$_6$(DMSO)$_8$ formed in dimethyl sulfoxide solutions are compatible with the spectral fingerprints measured at high concentrations of lead iodide. This finding suggests that the formation of polynuclear lead-halide complexes should be accounted for in the interpretation of optical spectra of LHP precursor solutions.