The phenomenon of dielectric switching has garnered considerable
attention due to its potential applications in electronic and photonic
devices. Typically, hybrid organic–inorganic perovskites, HOIPs,
exhibit a binary (low–high) dielectric state transition, which,
while useful, represents only the tip of the iceberg in terms of functional
relevance. One way to boost the versatility of applications is the
discovery of materials capable of nonbinary switching schemes, such
as three-state dielectric switching. The ideal candidate for that
task would exhibit a trio of attributes: two reversible, first-order
phase transitions across three distinct crystal phases, minimal thermal
hysteresis, and pronounced, step-like variations in dielectric permittivity,
with a substantial change in its real part. Here, we demonstrate a
one-dimensional lead halide perovskite with the formula (CH3)2C(H)NH3)PbI3, abbreviated as ISOPrPbI3, that fulfills these criteria and demonstrates three-state
dielectric switching within a narrow temperature range of ca. 45 K.
Studies on ISOPrPbI3 also revealed the polar nature of
the low-temperature phase III below 266 K through pyrocurrent experiments,
and the noncentrosymmetric character of the intermediate phase II
and low-temperature phase III is confirmed via second harmonic generation
measurements. Additionally, luminescence studies of ISOPrPbI3 have demonstrated combined broadband and narrow emission properties.
The introduction of ISOPrPbI3 as a three-state dielectric
switch not only addresses the limitations posed by the wide thermal
gap between dielectric states in previous materials but also opens
new avenues for the development of nonbinary dielectric switchable
materials.