The development of broadband emitters based on metal
halide perovskites
(MHPs) requires the elucidation of structure–emission property
correlations. Herein, we report a combined experimental and theoretical
study on a series of novel low-dimensional lead chloride perovskites,
including ditopic aromatic cations. Synthesized lead chloride perovskites
and their bromide analogues show both narrow and broad photoluminescence
emission properties as a function of their cation and halide nature.
Structural analysis shows a correlation between the rigidity of the
ditopic cations and the lead halide octahedral distortions. Density
functional theory calculations reveal, in turn, the pivotal role of
octahedral distortions in the formation of self-trapped excitons,
which are responsible for the insurgence of broad emission and large
Stokes shifts together with a contribution of halide vacancies. For
the considered MHP series, the use of conventional octahedral distortion
parameters allows us to nicely describe the trend of emission properties,
thus providing a solid guide for further materials design.