Charge transport layers have been found to be crucial for high-performance perovskite solar cells (PSCs). SnO₂ has been extensively investigated as an alternative material for the traditional TiO₂ electron transport layer (ETL). The challenges facing the successful application of SnO₂ ETLs are degradation during the high-temperature process and voltage loss due to the lower conduction band. To achieve highly efficient PSCs using a SnO₂ ETL, low-temperature-processed mesoporous TiO₂ (LT m-TiO₂) was combined with compact SnO₂ to construct a bilayer ETL. The use of LT m-TiO₂ can prevent the degradation of SnO₂ as well as enlarge the interfacial contacts between the light-absorbing layer and the ETL. SnO₂/TiO₂ bilayer-based PSCs showed much higher power conversion efficiency than single SnO₂ ETL-based PSCs.

Wide-bandgap (WBG) perovskite solar cells (PSCs) are promising for tandem photovoltaics, but their performance is limited by substantial voltage losses from defect-mediated non-radiative recombination at perovskite/charge-transport-layer interfaces. While 3D/2D perovskite heterostructures can mitigate these losses, conventional solution-based approaches require the reconstruction of the underlying 3D perovskite surface, limiting control over the resulting 2D phase and thickness. This paper presents a hot-pressing transfer (HPT) strategy wherein a preformed n = 1 Ruddlesden–Popper 2D perovskite layer is directly transferred onto a WBG 3D perovskite. By decoupling 2D perovskite formation from the underlying 3D surface, HPT avoids direct solvent exposure and solvent-driven surface reconstruction during heterointerface assembly. The transferred 2D layer passivates surface defects, suppresses trap-assisted non-radiative recombination, and facilitates interfacial charge transport. A 3D/2D PSC incorporating a 1.73 eV WBG perovskite exhibits a power conversion efficiency of 17.49%, compared with 15.30% for the 3D control, primarily because of increases in open-circuit voltage (Voc) and fill factor. The non-radiative Voc loss decreases from 289 to 211 mV, and the 3D/2D devices exhibit greater ambient-storage stability than the 3D controls. These results establish HPT as an effective strategy for constructing controlled 3D/2D heterostructures for efficient and stable WBG perovskite photovoltaics.