Solvent-Mediated Formation of Quasi-2D Dion-Jacobson Phases on 3D Perovskites for Inverted Solar Cells Over 23% Efficiency

2D-on-3D (2D/3D) perovskite heterostructures present a promising strategy to realize efficient and stable photovoltaics. However, their applicability in inverted solar cells is limited due to the quantum confinement of the 2D-layer and solvent incompatibilities that disrupt the underlying 3D layer, hampering electron transport at the 2D/3D interface. Herein, solvent-dependent formation dynamics and structural evolution of 2D/3D heterostructures are investigated via in situ X-ray scattering. It is revealed that solvent interaction with the 3D surface determines the formation sequence and spatial distribution of quasi-2D phases with n = 2-4. Isopropanol (IPA) reconstructs the perovskite into a PbI2-rich surface, forming a strata with smaller n first, followed by a thinner substratum of larger n. In contrast, 2,2,2-Trifluoroethanol (TFE) preserves the 3D surface, promoting the formation of uniformly distributed larger n domains first, and smaller n last. Leveraging these insights, Dion-Jacobson perovskites are used with superior charge transport properties and structural robustness to fabricate 2D/3D heterostructures dominated by n & GE; 3 and engineer a favorable energy landscape for electron tunneling. Inverted solar cells based on 3-Aminomethylpyridine and TFE achieve a champion efficiency of 23.60%, with Voc and FF of 1.19 V and 84.5%, respectively, and superior stabilities with t94 of 960 h under thermal stress. This study elucidates the formation dynamics and film structure of 2D-Dion-Jacobson phase on a template of 3D triple-cation perovskite films via in situ X-ray scattering. The solvent-induced surface reconstruction of the template allows the control of phase and phase distribution in 2D films. The tailored energy landscape of 2D/3D heterostructures leads to highly efficient and stable inverted perovskite solar cells.image