Photoinduced iodide repulsion and halides-demixing in layered perovskites

• Published in: Materials today. Nano Vol. 18; p. 100197
• Main Authors: Liu, Y., Wang, M., Ievlev, A.V., Ahmadi, A., Keum, J.K., Ahmadi, M., Hu, B., Ovchinnikova, O.S.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Ltd 01.06.2022; Elsevier
• Subjects: Chemical distribution; MATERIALS SCIENCE; Metal halide perovskites; Phase segregation; Spacer cation effect; Metal halide perovskites; Phase segregation; Chemical distribution; Spacer cation effect
• ISSN: 2588-8420; 2588-8420
• DOI: 10.1016/j.mtnano.2022.100197

Mixing halides in metal halide perovskites (MHPs) is an effective approach for adjusting the MHPs bandgap for applications in tandem solar cells. However, mixed-halide (MH-) MHPs undergo light-induced phase segregation (LIPS) under continuous illumination. Therefore, understanding the mechanism of LIPS is necessary for developing stable MH-MHPs. In this work, we investigated LIPS in layered (L) MHPs and discovered a critical role of spacer cations in LIPS. Through probing chemical changes of LIPS, we unveil light-induced iodide repulsion and the formation of Br-rich-phase in illuminated regions during LIPS. This discovery also gives insight into the LIPS process in three-dimensional (3D) MHPs. By further investigating LIPS in 3D MHPs, we reveal that LIPS induces not only the formation of Br-rich and I-rich domains but also an overall change of halide distribution along the film thickness direction. Moreover, LIPS is more significant in bulk due to a larger population of photogenerated charge carriers. Overall, this study reveals the chemical mechanism of LIPS in MHPs and its potential effect on device performance, offering insight into understanding the LIPS mechanism and improving the stability of MHPs. [Display omitted] •2D space cation has a significant effect on the photoinduced phase segregation in 2D metal halide perovskites (MHPs).•Oxygen influences the chemical distribution in 2D MHPs that is resulted from photoinduced phase segregation.•Photoinduced phase segregation not only leads to the formation of Br- and I- rich domains but also induces chemical distribution change in the vertical direction of MHPs film.•Photoinduced phase segregation is more significant in the bulk of MHPs thin film than surface and interface.