Niobium‐Carbide MXene Modified Hybrid Hole Transport Layer Enabling High‐Performance Organic Solar Cells Over 19%

Abstract Niobium‐carbide (Nb 2 C) MXene as a new 2D material has shown great potential for application in photovoltaics due to its excellent electrical conductivity, large surface area, and superior transmittance. In this work, a novel solution‐processable poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS)‐Nb 2 C hybrid hole transport layer (HTL) is developed to enhance the device performance of organic solar cells (OSCs). By optimizing the doping ratio of Nb 2 C MXene in PEDOT:PSS, the best power convention efficiency (PCE) of 19.33% can be achieved for OSCs based on the ternary active layer of PM6:BTP‐eC9:L8‐BO, which is so far the highest value among those of single junction OSCs using 2D materials. It is found that the addition of Nb 2 C MXene can facilitate the phase separation of the PEDOT and PSS segments, thus improving the conductivity and work function of PEDOT:PSS. The significantly enhanced device performance can be attributed to the higher hole mobility and charge extraction capability, as well as lower interface recombination probabilities generated by the hybrid HTL. Additionally, the versatility of the hybrid HTL to improve the performance of OSCs based on different nonfullerene acceptors is demonstrated. These results indicate the promising potential of Nb 2 C MXene in the development of high‐performance OSCs.