An Inverted Layer-by-Layer Process to Enable Ultrasmooth MXene-Ag Nanowire Hybrid Electrode for Organic Photovoltaics

To realize flexible and wearable electronic devices in the future, it is important to develop flexible transparent electrodes while replacing indium tin oxide-based transparent electrodes. Herein, a highly conductive transparent electrode based on hybrid materials of MXene nanosheet films and Ag nanowires (AgNWs) is reported, which synergistically combines the advantageous properties of each material. MXene/AgNW/colorless polyimide (cPI) hybrid electrode is prepared utilizing reverse sequential processing of MXene nanosheets and AgNWs and exhibits significantly improved conductivity and transmittance compared with the MXene/cPI electrode. Furthermore, owing to the abundant hydrophilic termination groups (-O and -OH) on the MXene surface, the MXene/AgNW/cPI hybrid electrode shows hydrophilic surface properties and a highly uniform film. Therefore, the MXene/AgNW/cPI hybrid electrode exhibits higher transmittance at 550 nm to 79% than MXene/cPI electrode (59%) and considerably lower sheet resistance (13.08 ohm sq(-1)) than MXene/cPI electrode (113.6 ohm sq(-1)). Flexible organic photovoltaic devices fabricated with MXene/AgNW/cPI hybrid electrode achieve higher power conversion efficiency of 10.3% compared with 6.70% of the corresponding MXene/cPI electrode. These results provide the great potential of Ti3C2-based MXene hybrid electrode as a flexible transparent electrode, paving the way for various and wider range of applications include solar cells and light-emitting diodes.