Probe of the excitonic transitions and lifetimes in quasi-2D organic–inorganic halide perovskites

Traditional organic–inorganic halide perovskites (OIHPs), in which perovskites layers are separated by an organic spacer material, have been mainly explored for photovoltaics devices, but they also offer promises for nonlinear optics and quantum light applications. These attributes include (a) high quantum efficiency, (b) large binding energy of excitons in low-dimensional structures, (c) polarons of long coherence times at room temperature, and (d) a large spin–orbit coupling. OIHP systems can be engineered to have photoluminescence (PL) emissions from UV to IR regions, in addition to power conversion efficiencies, in excess of 24%. This class of materials offers broad tunability of its properties, through controlling the number of atomic layers in the quantum well, tuning the organic spacer thickness, or even engineering the composition with exotic dopants. In this work, we present PL and time-resolved PL measurements of quasi-2D BA2PbI4 and provide new insights on the temperature dependence of their excitonic dynamics and fine structures of their PL emissions. We observed long lifetimes, which can result from the formation of large polarons, screening the Coulomb interactions of the charge carriers and reducing the scattering of the carriers with charge defects.