Two-Dimensional Lead Iodide Perovskites with Extremely Reduced Dielectric Confinement: Embedded Self-Erasing Second-Harmonic Generation Switching, Thermochromism, and Photoluminescence
Title: Two-Dimensional Lead Iodide Perovskites with Extremely Reduced Dielectric Confinement: Embedded Self-Erasing Second-Harmonic Generation Switching, Thermochromism, and Photoluminescence
Authors: M. Mączka, J. K. Zaręba, A. Nowok, N. Sokołowski, A. Sieradzki, A, Gągor, M. Ptak
Journal: Chemistry of Materials
DOI: 10.1021/acs.chemmater.4c02394
In their recent article, prof. Mączka’s group reported studies of two layered lead iodide perovskites comprising ethanolammonium and propanolammonium cations with extremely reduced dielectric confinement. The research focused on the detailed characterization of these compounds using multitechnique approach.
It has been demonstrated that the photoactive phases I transform at higher temperatures to new metastable phases II. On cooling, phases II either revert to phases I (after some time) or exhibit their own phase transitions below room temperature to metastable phases III. Linear optical and dielectric properties of these new phases have been explored, and mechanisms of the phases transitions have been explained.
The most interesting discovery concern, however, nonlinear optical (NLO) behaviour of the ethanolammonium analogue. Our studies showed that the metastable high-temperature phase II lacks second-harmonic generation (SHG) activity but the SHG response is observed in the metastable low-temperature phase III. The metastability of acentric phase III and supercooled centric phase II is harnessed to introduce a new type of NLO functionality, namely, embedded self-erasing SHG switching. The “embedded” scheme requires thermodynamically unstable crystal phases, one of which is noncentrosymmetric, and necessitates thermal activation, such as annealing followed by cooling. This unconventional route of triggering NLO responses, along with spontaneous reversion to the thermodynamically stable centrosymmetric phase I, enables self-erasing switching between the SHG-on and SHG-off states.
Highlights:
- Two 2D lead iodide perovskites have been synthesized
- Structural, linear optical, NLO, phonon and electrical properties have been described
- The molecular dynamics of organic cations has been described
- New type of self-erasing NLO switch has been proposed
