Modulation of Charge Transport from Two-Dimensional Perovskites to Industrial Charge Transport Layers by the Organic Spacer-Dependent Exciton-Phonon Interactions

In the past decade, two-dimensional (2D) perovskite surface treatment has emerged as a promising strategy to improve the performance of three-dimensional (3D) perovskite solar cells (PSCs). However, systematic studies on the impact of organic spacers of 2D perovskites on charge transport in 2D/3D PSCs are still lacking. Here, using 2D perovskite film/C₆₀ heterostructures with different organic spacers [butylamine (BA), phenylethylamine (PEA), and 3-fluorophenethylamine (m-F-PEA)], we systematically investigated the carrier diffusion and interfacial transfer process. Using a 2D perovskite film with a thickness of ∼7 nm, we observed subtle differences in electron transfer time between 2D perovskites and C₆₀ layers, which can be attributed to limited thickness and similar electron coupling strength. However, with the thickness of 2D perovskite increasing, electron transfer efficiency in the (BA)₂PbI₄/C₆₀ heterostructure exhibits the most rapid decrease due to poor carrier diffusion of (BA)₂PbI₄ caused by stronger exciton-phonon interactions compared to (PEA)₂PbI₄ and (m-F-PEA)₂PbI₄ in thickness-dependent charge transfer research. Meanwhile, the fill factor of 2D/3D PSC treated with BAI exhibits the most rapid decrease compared to PEAI- and m-F-PEAI-treated 2D/3D PSCs with the concentration increase of passivators. This study indicates that it is easier to enhance open-circuit voltages and minimize the decrease of fill factor by increasing the concentration of passivators in 2D/3D PSCs when using passivators with a rigid molecular structure.