Spectral Dynamics and Multiphoton Absorption Properties of All-Inorganic Perovskite Nanorods.

All-inorganic perovskite (CsPbX, X = Cl, Br, I) nanorods (NRs) not only retain their inherent advantages such as a high photoluminescence quantum yield and broad wavelength tunability but also exhibit superior photophysical properties including their extremely strong multiphoton absorption (MPA). However, the spectral dynamics and MPA properties of CsPbX NRs have not been fully investigated. Here, we report comprehensive comparison studies on the femtosecond spectral dynamical properties of CsPb(BrCl), CsPbBr, and CsPb(BrI) NRs, including their influences on their hot-carrier cooling, biexciton lifetime, and biexciton binding energy. Interestingly, although the three kinds of perovskite NRs have similar diameters and lengths, they differ significantly in their nonlinear optical properties, among which the CsPb(BrI) displayed the greatest MPA cross sections. Furthermore, the multiphoton-excited stimulated emission of CsPb(BrCl) and CsPbBr NRs is demonstrated. This work indicates that CsPbX (X = Cl, Br, I) NRs are excellent candidates for exploring their applications in different optoelectronic devices.