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Two-dimensional (2D) and three-dimensional (3D) perovskite heterostructures have played a key role in advancing the performance of perovskite solar cells1,2. However, the migration of cations between 2D and 3D layers results in the disruption of octahedral networks, leading to degradation in performance over time3,4. We hypothesized that perovskitoids, with robust organic–inorganic networks enabled by edge- and face-sharing, could impede ion migration. We explored a set of perovskitoids of varying dimensionality and found that cation migration within perovskitoid–perovskite heterostructures was suppressed compared with the 2D–3D perovskite case. Increasing the dimensionality of perovskitoids improves charge transport when they are interfaced with 3D perovskite surfaces—this is the result of enhanced octahedral connectivity and out-of-plane orientation. The 2D perovskitoid (A6BfP)8Pb7I22 (A6BfP: N-aminohexyl-benz[f]-phthalimide) provides efficient passivation of perovskite surfaces and enables uniform large-area perovskite films. Devices based on perovskitoid–perovskite heterostructures achieve a certified quasi-steady-state power conversion efficiency of 24.6% for centimetre-area perovskite solar cells. We removed the fragile hole transport layers and showed stable operation of the underlying perovskitoid–perovskite heterostructure at 85 °C for 1,250 h for encapsulated large-area devices in ambient air.We find that 2D–3D perovskitoid passivation applied to perovskite solar cells impedes cation migration and decreases carrier recombination at the interface, providing enhanced operating stability at elevated temperatures and increased power conversion efficiencies. [ABSTRACT FROM AUTHOR]

The open-circuit voltage (VOC) deficit in perovskite solar cells is greater in wide-bandgap (over 1.7 eV) cells than in perovskites of roughly 1.5 eV (refs. 1,2). Quasi-Fermi-level-splitting measurements show VOC-limiting recombination at the electron-transport-layer contact3–5. This, we find, stems from inhomogeneous surface potential and poor perovskite–electron transport layer energetic alignment. Common monoammonium surface treatments fail to address this; as an alternative, we introduce diammonium molecules to modify perovskite surface states and achieve a more uniform spatial distribution of surface potential. Using 1,3-propane diammonium, quasi-Fermi-level splitting increases by 90 meV, enabling 1.79 eV perovskite solar cells with a certified 1.33 V VOC and over 19% power conversion efficiency (PCE). Incorporating this layer into a monolithic all-perovskite tandem, we report a record VOC of 2.19 V (89% of the detailed balance VOC limit) and over 27% PCE (26.3% certified quasi-steady state). These tandems retained more than 86% of their initial PCE after 500 h of operation.Because open-circuit voltage deficit is greater in wide-bandgap perovskite solar cells, the authors introduce diammonium molecules to modify perovskite surface states and achieve a more uniform spatial distribution of surface potential, enabling record voltage all-perovskite tandem solar cells. [ABSTRACT FROM AUTHOR]