Hole Transfer Dynamics in Thin Films of Mixed-Dimensional Quasi-2D Perovskites

TL;DR

This study explores charge transfer in mixed-dimensional quasi-2D perovskite thin films, revealing rapid hole transfer between phases and highlighting the need to minimize the n=1 phase to improve solar cell efficiency.

Contribution

It provides new insights into the charge transfer dynamics across different phases in quasi-2D perovskites with a specific morphology gradient.

Findings

Efficient hole transfer occurs within tens of picoseconds between phases.

The n=1 phase acts as a hole-blocking layer, hindering charge transport.

Minimizing the n=1 phase can enhance charge carrier separation.

Abstract

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, we investigate the link between charge transport dynamics and morphology 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, we observe efficient hole transfer to the n=2 and n=3 phases occurring within few tens of picoseconds after excitation. 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.