How Exciton Interactions Control Spin-Depolarization in Layered Hybrid Perovskites
Sean A. Bourelle, Ravichandran Shivanna, Franco V. A. Camargo, Soumen Ghosh, Alexander J. Gillett, Satyaprasad P. Senanayak, Sascha Feldmann, Lissa Eyre, Arjun Ashoka, Tim W. J. van de Goor, Haralds Āboliņš, Thomas Winkler, Giulio Cerullo, Richard H. Friend, Felix Deschler
Abstract
Using circularly polarized broadband transient absorption, time-resolved circular photoluminescence, and transient Faraday rotation spectroscopy, we report that spin-dependent interactions have a significant impact on exciton energies and spin depolarization times in layered Ruddlesden–Popper hybrid metal-halide perovskites. In BA2FAPb2I7, we report that room-temperature spin lifetimes are largest (3.2 ps) at a carrier density of ∼1017 cm–3 with increasing depolarization rates at higher exciton densities. This indicates that many-body interactions reduce spin-lifetimes and outcompete the effect of D’yakonov-Perel precessional relaxation that has been previously reported at lower carrier densities. We further observe a dynamic circular dichroism that arises from a photoinduced polarization in the exciton distribution between total angular momentum states. Our findings provide fundamental and application relevant insights into the spin-dependent exciton–exciton interactions in layered hybrid perovskites.