Abstract
We employ a fine-tuned theoretical framework, combining ab initio molecular dynamics (AIMD), density functional theory (DFT), and time-dependent (TD) DFT methods, to investigate the interactions and optical properties of the iodoplumbates within the low coordinative γ-butyrolactone (GBL) solvent environment, widely employed in the perovskite synthesis. We uncover the extent of GBL coordination to PbI2 investigating its relation to the solvated PbI2 optical properties. The employed approach has been further validated by comparison with the experimental UV–vis absorption spectrum of PbI2 in GBL solvent. A comparison with other solvents, commonly employed in the perovskite synthesis, such as N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is also reported. The methodology developed in this work can be reasonably extended to the investigation of similar systems.
Highlights
Coordination to PbI2 investigating its relation to the solvated PbI2 optical properties
To uncover the interactions of the PbI2 system at the atomic level, we carried out ab initio molecular dynamics (AIMD) simulation of the solvated PbI2 complexes and we evaluated the energetics and the geometries of static PbI2(GBL)n complexes by means of density functional theory (DFT) methods
Letter occupied by a single GBL molecule, and we ran a first short (∼5 ps) molecular dynamics simulation of an initial model with 4 GBL molecules
Summary
PbI2 by GBL molecules, i.e., average longer Pb−O bond lengths. Interestingly, from the experimental spectrum we can notice a small absorption shoulder at 367 nm, that was saosslvigennetds.15t,o18,3t1h−e33PbTI3h−is species feature both in is not GBL and in other detected from our calculation, since at present we are not considering other iodoplumbates than PbI2. As reported previously,[18] the formation energies of iodoplumbates in GBL are always lower than those in DMF and DMSO, confirming the lower coordinative power of GBL that, as already said, reflects on the simulated spectra We found that PbI2 is coordinated on average by three GBL molecules, that are able to anchor through pincher-type interaction, i.e., involving both the carbonyl and the alkoxy oxygen atoms These interactions are weaker than those established by higher coordinative solvents, such as DMSO or DMF, with direct consequences on many aspects, such as the solubility of precursors and solvent evaporation rate, that in turn influence the way perovskite grows, the morphology and the type of defects that will be found in the final material.
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