Low-Cost Multilayer MXene Doped Carbon Electrode for High-Performance Hole-Transport-Layer-Free Perovskite Solar Cells

Hole-transport-layer (HTL)-free carbon-based PSCs (C-PSCs) show attractive commercial potential due to low production costs, simplifying manufacturing process, and relatively high stability. The defect passivation of perovskite and energy-level modification of the carbon electrode are crucial to further improve the PCE and stability of C-PSCs. Herein, a low-cost multilayer Ti₃C₂T_x MXene is doped into carbon paste to construct MXene@carbon electrode for C-PSCs. The preparation of multilayer MXene is simple and cost-effective due to only requiring the etching of the MAX phase. The incorporation of MXene appropriately increases the work function, providing a suitable energy level alignment between perovskite and MXene@carbon. The surface T_x groups of MXene can form favorable interaction with the oxygen-containing functional groups of graphite, facilitating the good dispersion of MXene in the carbon paste, which improve the interface contact between perovskite and MXene@carbon and the conductivity and morphology of MXene@carbon electrode. Therefore, the MXene@carbon C-PSCs show enhanced charge transport and extraction and reduced defects and charge recombination and thus achieve significantly improved photovoltaic performance and operational stability. Compared with the conrtol MAPbI₃ device with pristine carbon electrode (PCE of 12.69%), the MXene@carbon device exhibits obviously higher PCE of 16.00%, which is top-level for HTL-free MAPbI₃ C-PSCs without perovskite passivators. Moreover, the average PCE (14.68%) of the MXene@carbon devices was also significantly higher than that (12.37%) of the control devices. The impressive results indicate the great potential of the MXene doped carbon electrode for high-performance C-PSCs.