Working Mechanisms of Triple-Oxide Mesoporous Hole-Transport-Layer-Free Printable Perovskite Solar Cells via Impedance Spectroscopy

All-printed mesoporous perovskite solar cells (PSCs) show great potential for scalable photovoltaic technologies, yet direct identification of their key working mechanisms by impedance spectroscopy (IS) is not well-established. IS response of printable hole transport layer (HTL)-free triple mesoporous (mp) TiO₂/ZrO₂/ITO PSCs with varying TiO₂electron transport layer (ETL) thicknesses (500–1200 nm) reveals strong interplay between the mesoporous scaffold architecture and charge carrier dynamics, significantly impacting resistive and capacitive features of the devices. The emergence of an intermediate-frequency feature can be related to chemical capacitance of the mp-TiO₂layer, a phenomenon commonly associated with dye-sensitized solar cells, decoupling recombination, and key transport phenomena for both charge carriers. An updated equivalent circuit model, incorporating chemical capacitance and associated transport/recombination resistances can capture these effects. These findings provide valuable insights into the role of mesoporous scaffold engineering in printable PSCs and offer a robust characterization tool for optimizing scalable photovoltaic architectures.