2D multilayered perovskites introduced by Calabrese (JACS 1991) share similarities with 3D perovskites including direct electronic band gap, sizeable optical absorption, small effective masses, Rashba-like effects. Calabrese’s Ruddlesden-Popper phases were completed more recently by "Alternative cations in the interlayer" (Soe, JACS 2017) and Dion-Jacobson (Mao, JACS 2018) phases, leading to a consistent classification of multilayered perovskites in relation with the chemistry of the compounds or the crystallographic order along the stacking axis (Blancon, Nature Nano 2020). 2D multilayered thus afford extensive chemical engineering possibilities, and exhibit other features related to tuneable quantum and dielectric confinements, strong lattice anisotropy, strong exciton interactions, more complex combinations of atomic orbitals and lattice dynamics.
Exploring the potential of 2D perovskites for PV and the association of 2D and 3D perovskites in solar cell architectures is a long-term joint project with colleagues in US (Prof. A. Mohite, LANL then Rice Univ., Prof. M. Kanatzidis Northwestern Univ.) that we started years ago including the first breakthrough on 2D perovskite for PV (Tsai Nature 2016). This approach is in line with Snaith’s recent viewpoint (Science 2024) about perovskite solar cell architecture trends: “a growing consensus is forming about the requirements for an ideal perovskite interface: the elimination or repair of surface interface defects, the design of a rational energy landscape to satisfy selective carrier collection, the minimization of strain and stress, and the improvement of physical robustness and adhesion”. 
This will be illustrated by recent combined experimental and theoretical studies on excitons, formation of edge states, hot carrier effects and carrier localization (Blancon Science 2017, Blancon Nature Comm. 2018, Li. Nature Nano 2022, Zhang Nature Phys. 2023).  2D multilayered perovskites have exhibited very early improved device stability under operation. More, combined in 2D/3D bilayer structures using new versatile growth methods, excellent solar cell device stability can be achieved (Sidhik, Science 2022). Band alignment calculations nicely explain the difference of performances for ni-p or p-i-n devices. Our lattice mismatch concept (Kepenekian, Nanoletters 2018) shall provide further guidance for the choice of the proper 2D/3D combinations, leading to enhanced stability for 3D-based solar cells (Sidhik, Science 2024).