Exploring the Impedance Spectroscopy in Hole-Conductor-Free Mesoscopic Perovskite Solar Cells

Abstract

This study focuses on the hole-conductor-free printable mesoscopic perovskite solar cells (p-MPSCs), which employ carbon electrodes and mesoporous scaffold structures, offering advantages of low cost and high stability with significant commercial potential. Although progress has been made in structural and performance optimization, the carrier dynamics under operational conditions remain insufficiently understood. In this work, we introduced 5-ammonium valeric acid iodide (5-AVAI) as an additive, significantly enhancing device stability and enabling consistent performance during prolonged impedance spectroscopy (IS) measurements. For the first time, we established a dedicated equivalent circuit model for p-MPSCs. Through thickness-dependent IS analysis, we elucidated the physical significance of each circuit element and its correlation with the functional layer thickness. In addition, the influence of light intensity under working conditions was systematically studied: Within the range of < 800 W/cm², enhanced light can slow down recombination and charge accumulation, but excessive light intensity (> 800 W/cm²) can lead to a decrease in low-frequency lifetime. Notably, we observed for the first time that carrier extraction and transport time scales remain insensitive to bias voltage variations. These findings provide fundamental insights into the charge extraction and recombination mechanisms in p-MPSCs under operational conditions, offering critical theoretical guidance for their industrial development.