Exciton-Carrier Dynamics in 2D Perovskites

2D perovskites has become a major topic in the field of perovskite optoelectronics. Here, we aim to unravel the ultrafast dynamics governing the evolution of charge carriers and excitons. We use a combination of ultrabroadband time-resolved THz spectroscopy (TRTS) and fluorescence upconversion spectroscopy to observe and model this evolution. We find that sequential carrier cooling and exciton formation best explain the observed dynamics, where exciton-exciton interactions play an important role in the form of Auger heating and biexciton formation. In fact, we can show that the presence of a longer-lived population of carriers is due to these processes and not to a Mott transition. Therefore, in these materials, excitons still dominate at laser spectroscopy excitation densities. We use kinetic modeling to compare the phenethylammonium and butylammonium organic cations while investigating the stability of the resulting films. In addition, we demonstrate the capability of using ultrabroadband TRTS to study excitons in large binding energy semiconductors through spectral analysis at room temperature.