MXene-Enhanced Nanoscale Photoconduction in Perovskite Solar Cells Revealed by Conductive Atomic Force Microscopy

The use of MXene materials in perovskite solar cells (PSCs) has received significant interest due to their distinct features that result from the termination of functional groups and the oxidation of MXene. Herein, we have used photoconductive atomic force microscopy (pcAFM) to map the local (nanoscale) photovoltaic performances of the Ti₃C₂T MXene nanosheet-integrated TiO₂ (MXene@TiO₂) electron transport layer-based PSCs to determine the influence of the treatment on the microscopic charge flow inside the devices. At different applied voltages, the morphology and current have been simultaneously measured with nanoscale resolution from the top surfaces of the solar cells without back contacts. The PSCs based on MXene@TiO₂ exhibit more enhanced current flow across the grains than the only TiO₂-based PSCs. At zero applied bias, the average local photocurrent for MXene-integrated PSCs is several times higher than the reference PSCs and decreases gradually when the positive bias is increased until the open circuit voltage. Considerable differences were also observed in the short circuit current among different locations that appear identical in AFM topography. Our findings reveal the potential of MXene-integrated ETLs to enhance the nanoscale photoconduction and inherent characteristics of the active layers, thereby improving the performance of the polycrystalline photovoltaic devices.