Temporally Resolved Three Perovskite Structures in One Pot

Chatterjee, Tathagata (2023) Temporally Resolved Three Perovskite Structures in One Pot. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS dissertation of Tathagata Chatterjee (18MS158),) Thesis_18MS158.pdf - Submitted Version Restricted to Repository staff only Download (5MB)

Abstract

Throughout the last decade, lead halide perovskites have emerged as a new exciting, and promising class of semiconducting materials showing various tunable properties leading to a wide range of applications. Confining the perovskite particles at the nanosize domain has also brought up a new avenue of research concerning various induced phase transitions and their structure-property correlations. This is especially interesting due to the challenges faced during synthesizing the nanocrystals, maintaining their stability, and exerting precise control over the phase and morphology. From the synthesis perspective, numerous stoichiometric methods can be employed to obtain the desired phases, but the synthesis of phases based on temporal resolution still needs to be explored. This work shows that the black-colored three-dimensional (3D) α-FAPbI₃ nanocrystals (NCs) can be transformed to two new lower-dimensional phases (Red and Yellow) by a facile single-pot synthesis technique. This post-modification is a facile solvent-interface technique developed with two immiscible layers and has been resolved with respect to time and temperature. Detailed crystal structure analysis and study of optical properties reveals the 2D Ruddlesden-Popper (RP) structure of the Red phase showing multilayer diffraction and a lower dimensional Yellow phase. A series of control experiments also demonstrate the iodide anion to be the actual phase-transforming agent, which induces facet opening and internal rearrangement of the structures with time. Furthermore, applying heat to the Red and Yellow phases show thermochromic properties with the origin of a new red phase having a higher periodicity value.

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