Elucidating the Structure-Property Relationship and Ultrafast Exciton/Charge Carrier Dynamics of Layered Cs4CuSb2Cl12 Double-Perovskite Microcrystals

Abstract

In recent times, layered double perovskites have attracted considerable attention due to their nontoxic nature, structural stability in ambient conditions, and ability to tune optoelectronic properties through the interplay between two metal ions. To better comprehend the utility of this promising class of materials to be used as absorber materials in solar cells, it is important to understand the nature of band-gap and excited-state dynamics. In this work, we present a comprehensive study on the microcrystals of Cs4CuSb2Cl12, a relatively new class of double perovskites, which have emerged as a propitious contender. Using dispersion-corrected density functional theory, we study the nature of the band structure and identify the structural and energetic parameters that are also tested experimentally. Further, using femtosecond transient absorption spectroscopy, we show that depending on the excitation wavelength, the excited-state relaxation mechanism involves either excitons or free charge carriers. One crucial observation is the solvent dependence of the relaxation rates of carriers, opening up the possibilities of solvent control of charge carrier dynamics. © 2023 American Chemical Society.