Titanium Carbide MXene Hole Contacts for CdTe Photovoltaics

CdTe is a high-efficiency thin-film photovoltaic (PV) technology that has seen tremendous commercial success over the past decade. Yet despite the improvement of other device characteristics, the fabrication of an ohmic hole back contact layer has remained a challenge due to the high ionization potential of CdTe, which limits the external potential that can be feasibly reached even as other characteristics ofthe device improve. MXenes, a family of 2D materials with rapidly growing scientific and commercial interest, offer a promising route to forming low-cost, low-barrier contacts due to their demonstrated high work function, metallic conductivity, and facile solution processing from benign solvents. Here, it is shown that Ti3C2Tx MXene films processed from an aqueous colloidal dispersion can perform as a highly efficient hole contact material for CdTe solar cells, resulting in high power-conversion efficiencies. The role of the Schottky barrier formation in Ti3C2Tx-contacted CdTe devices is probed, and potential pathways for the future development of this potent combination of materials are elucidated. The modularity of the expansive MXene family of materials presents a promising strategy for developing next-generation hole contacts for CdTe solar cells.