Inhibiting the appearance of green emission in mixed lead halide perovskite nanocrystals for pure red emission

Journal article : Letter

Mixed halide perovskites exhibit promising optoelectronic properties for next-generation light-emitting diodes due to their tunable emission wavelength that covers the entire visible light spectrum. However, these materials suffer from severe phase segregation under continuous illumination, making long-term stability for pure red emission a significant challenge. In this study, we present a comprehensive analysis of the role of halide oxidation in unbalanced ion migration (I/Br) within CsPbI₂Br nanocrystals and thin films. We also introduce a new approach using cyclic olefin copolymer (COC) to encapsulate CsPbI₂Br perovskite nanocrystals (PNCs), effectively suppressing ion migration by increasing the corresponding activation energy. Compared with that of unencapsulated samples, we observe a substantial reduction in phase separation under intense illumination in PNCs with a COC coating. Our findings show that COC enhances phase stability by passivating uncoordinated surface defects (Pb²⁺ and I^–), increasing the formation energy of halide vacancies, improving the charge carrier lifetime, and reducing the nonradiative recombination density.

Authors: Alanazi, M; Marshall, AR; Liu, Y; Kim, J; Kar, S

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Chemical Society
• Journal: Nano Letters
• Volume: 24
• Issue: 39
• Pages: 12045-12053
• Place of publication: United States
• Publication date: 2024-09-23
• Acceptance date: 2024-09-19
• DOI: 10.1021/acs.nanolett.4c01565
• EISSN: 1530-6992
• ISSN: 1530-6984
• Pmid: 39311748
• Language: English
• Keywords: phase segregation; mixed lead halide perovskites; halide sublimation; encapsulation; thin films; nanocrystals
• Subtype: Letter