Colloidal Synthesis and Photophysics of M Sb I (M=Cs and Rb) Nanocrystals: Lead-Free Perovskites.

Herein we report the colloidal synthesis of Cs Sb I and Rb Sb I perovskite nanocrystals, and explore their potential for optoelectronic applications. Different morphologies, such as nanoplatelets and nanorods of Cs Sb I , and spherical Rb Sb I nanocrystals were prepared. All these samples show band-edge emissions in the yellow-red region. Exciton many-body interactions studied by femtosecond transient absorption spectroscopy of Cs Sb I nanorods reveals characteristic second-derivative-type spectral features, suggesting red-shifted excitons by as much as 79 meV. A high absorption cross-section of ca. 10  cm was estimated. The results suggest that colloidal Cs Sb I and Rb Sb I nanocrystals are potential candidates for optical and optoelectronic applications in the visible region, though a better control of defect chemistry is required for efficient applications.