  The low ionization energy of an $A$ site molecule is a very important factor,
which determines the thermodynamical stability of $A$PbI$_3$ hybrid halide
perovskites, while the size of the molecule governs the stable phase at room
temperature and, eventually, the bandgap. It is challenging to achieve both a
low ionization energy and the reasonable size for the PbI$_3$ cage to
circumvent the stability issue inherent to hybrid halide perovskites. Here we
propose a new three-membered charged ring radical, which demonstrates a low
ionization energy that renders a good stability for its corresponding
perovskite and a reasonable cation size that translates into a suitable bandgap
for the photovoltaic application. We use ab initio calculations to evaluate a
polymorphism of the crystal structure of the proposed halide hybrid perovskite,
its stability and electronic properties in comparison to the mainstream
perovskites, such as the methylammonium and formamidinium lead iodide. Our
results highlight the importance of van der Waals interactions for predicting a
correct polymorphism of the perovskite vs hexagonal crystal structure.
