Origin of spectral broadening in rapidly rotated PbI2 nanostructures

Determine the origin of the broadened spectral features around 550 and 650 nm observed in rapidly rotated PbI2 nanostructures with a vertical pitch of approximately 8 nm.

Background

The supplementary analysis compares the optical spectra of the two limiting growth conditions: a static PbI2 film with no substrate rotation and a rapidly rotated film with a vertical pitch of approximately 8 nm. Although both samples exhibit weak chiroptical responses, the rapidly rotated sample displays additional broad spectral features near 550 and 650 nm. The authors explicitly state that the physical origin of this broadening is unresolved and offer only the hypothesis that it may be associated with crystallographic torsion induced during growth.