In Situ Exploration of the Structural Transition during Morphology‐ and Efficiency‐Conserving Halide Exchange on a Single Perovskite Nanocrystal

• Published in: Angewandte Chemie International Edition 2021-02, Vol.60 (5), p.2548-2553
• Main Authors: Karimata, Izuru, Tachikawa, Takashi
• Format: Article
• Language: English
• Subjects: Exchanging; Fabrication; ion exchange; metal halide perovskite; Metal halides; Miscibility; Morphology; Nanocrystals; Perovskites; Photoluminescence; Photons; Physicochemical properties; single-particle spectroscopy
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202013386

Controlled fabrication of semiconductor nanostructures with unique physicochemical properties is vital for future technologies. In this study, transformation from red‐emitting metal halide perovskite CH3NH3PbI3 nanocrystals (NCs) to green‐emitting CH3NH3PbBr3 NCs was achieved without significant morphological changes and loss of photoluminescence (PL) efficiency via a controlled halide exchange reaction. In situ single‐particle PL imaging along with detailed structural and elemental characterizations revealed that sudden cooperative transitions between two light‐emitting states via intermediate dark states with >100 s durations during halide exchange originate from two distinct defect‐mediated reconstruction processes with different activation energies (0.072 and 0.40 eV), leading to an isokinetic temperature of ca. 314 K, across a solid‐state miscibility gap between the I‐ and Br‐rich phases inside a single NC. In situ single‐particle photoluminescence imaging revealed that sudden cooperative transition from green‐emitting CH3NH3PbI3 perovskite nanocrystals to red‐emitting CH3NH3PbBr3 while maintaining their morphology and emission efficiency during halide exchange. The transformation proceeds via intermediate dark states with >100 s durations and originates from two distinct defect‐mediated processes with different activation energies.