Critical Roles of Octahedron Bilayer Surface/Interior Bromide Defects in Photodynamics of Multi-Quantum-Well-Structured Cesium Bismuth Bromide

We investigate theoretically the roles of the intrinsicpoint defectsin the photophysics of wide-bandgap multi-quantum-well-structuredCs(3)Bi(2)Br(9) based on the Shockley-Read-Hallstatistics and multiphonon recombination theory. The GW plus Bethe-Salpeter equation calculation reveals that thereis a prominent exciton peak below the interband absorption edge, andit clarifies the experimental debate. The most energetically favorablenative defects possess deep thermodynamic transition levels. The bromideself-interstitials within the octahedron bilayers exhibit as efficientcarrier trapping centers through the non-radiative multiphonon recombination,with a lifetime of 184 ns being on the same order of magnitude asthe experimental value. The octahedron bilayer surface bromide self-interstitialsaccount for the experimentally observed dominant blue luminescencein Cs3Bi2Br9. These results revealthat the intrinsic point defects at different sites of the multi-quantum-well-likeoctahedron bilayers play different roles in the photodynamics of suchunique layer-structured semiconductors.