These materials combine stability and tunable optical properties, making them ideal for smart, efficient photovoltaic devices capable of harvesting energy in both indoor and outdoor environments. The understanding of charge transfer processes in mixed-dimensional quasi-2D perovskites is crucial for their application in high-performance photovoltaic devices.
In this work, the link between charge transport dynamics and morphology is investigated in a thin film of quasi-2D perovskites (PEA₂MAₙ₋₁PbₙI₃ₙ₊₁), grown with a distinct dimensionality gradient, where the n = 1 phase is concentrated near the substrate and phases with higher dimensionality progressively increase in concentration toward the surface. By selectively exciting the n = 4 phase, efficient hole transfer to the n = 2 and n = 3 phases occurring within a few tens of picoseconds after excitation is observed. In contrast, the n = 1 phase acts as a hole-blocking layer, limiting the overall charge transport efficiency.
These results emphasize the critical importance of minimizing or eliminating the n = 1 layer to enhance charge carrier separation and transport, offering valuable insights into the optimization of quasi-2D perovskite-based solar cells.