Evidence for Increased Exciton Binding Energy at High Temperature in 2D Ruddlesden-Popper Lead Halide Perovskites

Cryogenic measurements of exciton binding energies are extremely common and, in the usual circumstances, are good analogs for a material’s room-temperature behavior. When studying the role of excitons in materials integrated into room-temperature devices like solar cells, it occasionally happens that the behavior observed in situ does not correspond to those cryogenic measurements. Such is the case in materials like methylammonium lead iodide, where the exciton[JK1] binding energy decreases with increasing temperature. In the least convenient case, a potential solar cell material will have a higher exciton binding energy than expected, impeding free carrier generation and requiring additional exciton dissociation mechanisms. Using temperature-dependent measurements of the excitonic diamagnetic shift coefficient conducted using the Rice Advanced Magnet with Broadband Optics (RAMBO) in pulsed magnetic fields up to 45 T, we present data for a methylammonium lead iodide-based Ruddlesden-Popper 2D perovskite. Our results provide evidence for a room-temperature exciton binding energy exceeding previous cryogenic measurements.