Three-State Dielectric Switching within a Narrow Temperature Range in Isopropylammonium Lead Iodide, a...

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.