Nat. Commun. 9, 2254 (2018)

The discovery of two-dimensional (2D) Ruddlesden–Popper halide perovskites (RPPs) has given new momentum to perovskites optoelectronics. Yet to enable a rapid technological progress towards their practical use a better understanding of many fundamental aspects, including the nature of their optical resonances, is urgently required. Now, Blancon et al. have developed and experimentally verified a model able to quantitatively describe thickness-dependent optical transitions in layered RPPs.

First, the researchers conduct low-temperature magneto-absorption measurements to extract the exciton reduced mass for 2D RPP crystals, with the number of constituting perovskite layers varying between one and five. This parameter serves as an input to build a theoretical model that accurately describes the electron–hole Coulomb interaction in thin semiconductors by taking into account the effects of dielectric confinement. The proposed model provides a theoretical solution to the binding energy of the exciton ground state and indicates the existence of a universal thickness-dependent scaling behaviour. Being of critical importance for the operation of perovskites optoelectronic devices, this fundamental parameter can be computed for any given number of perovskite layers based on the deduced scaling law.