Pivotal Role of A‑Site Cations in Tailoring the Band-Edge States, Optical Properties, and Stability of 0D Hybrid Indium Chlorides

Optoelectronic
properties of organic–inorganic hybrid perovskites
(ABX3) or metal halides are governed primarily by the B
and X-site ions due to their electronic contribution to the band edge.
The A-site cations do not directly participate in the band edge; instead,
they stabilize the crystal structures. Facilitating these A-site cations
to contribute to the band edge can enable an additional degree of
tunability to properties and expand the opportunities beyond B and
X ions. Here, we rationally employ different A-site cations based
on anilinium cations in Sb3+-doped zero-dimensional (0D)
indium chlorides and illustrate their contribution to the band-edge
states using experimental data and theoretical calculations. We demonstrate
that a change in the A-site cation results in a change in the octahedral
distance in the crystal structure. In addition to this, we show that
the frontier orbitals of hybrid indium chlorides are delocalized across
the inorganic and organic moieties, leading to significant changes
in their optical properties. Consequently, Sb3+-doped hybrid
indium chlorides show a broadband emission with a PLQY over 93% and
remarkable spectral and structural stability in five different solvents,
including water, for 21 days.