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

ABSTRACT

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.