Dynamic Symmetry Conversion in Mixed-Halide Hybrid Perovskite upon Illumination

• Published in: ACS energy letters 2021-11, Vol.6 (11), p.3858-3863
• Main Authors: Tominaka, Satoshi, Karimata, Izuru, Matsuoka, Takahide, Sakamoto, Moeri, Nakajima, Takahito, Ohara, Koji, Tachikawa, Takashi
• Format: Article
• Language: English
• ISSN: 2380-8195; 2380-8195
• DOI: 10.1021/acsenergylett.1c01798

Organic–inorganic hybrid halide perovskites (ABX3, where A = CH3NH3 + (methylammonium ion, MA); B = Pb2+; and X = Br–, I–, or Cl–) have excellent optoelectronic properties and are highly efficient photovoltaic materials, but their chemical instability impedes their development for use in next-generation solar cells, wherein they serve as the light-harvesting material. Here, we propose a mechanism of photoluminescence red-shift, a performance-loss phenomenon known as light-induced halide segregation, in mixed-halide perovskites upon illumination using in situ single-particle spectroscopy and synchrotron-based X-ray techniques. Our experimental analyses suggest a defect-assisted photoinduced transition from ordinary nonpolar phases to polar phases at the local scale within seconds is coupled with organic cation reorientation, which in turn narrows the bandgap; first-principles calculations quantitatively supported this result. Our findings provide deeper insights into the nature of local polar domains in hybrid perovskite materials and help improve device stability and efficiency.