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 TiO2 electron 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-TiO2 layer, 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.