Bright and dark excitons in two-dimensional hybrid perovskites film*

Recently 2D hybrid organic-inorganic perovskites (2D-HOIP) with Ruddlesden-Popper structure have been studied extensively. Due to dielectric confinement and quantum confinement, excitons in 2D-HOIP have much larger binding energy and smaller radius compared with their 3D HOIP counterparts; consequently, excitonic effects are more pronounced in these systems. In this work, we present a comprehensive study of the exciton fine structure utilizing magnetic field induced polarization of photoluminescence in a model 2D-HOIP, 2D-phenethylammonium lead iodide (2D-PEPI), both in Faraday and Voigt configurations with fields up to 25 Tesla. From the exciton field induced circular and linear polarizations we have identified two pairs of exciton states: the ‘bright’ exciton pair (X/Y) and the ‘dark’ exciton pair D/Z. Their related zero-field splitting (fine structure) and g-values have been determined.