Stepwise regulating the work function of Ti3C2Tx MXene by charge transfer doping scheme for optoelectronic applications

MXenes have inspired growing exploration fervor for the charming and adjustable material features. Regulating their work function is urgently desired for developing MXene-based electronic and optoelectronic devices. Nonetheless, the surface termination-related material properties of MXenes make it rather challenging to discretely tune the work function without altering other fundamental material characteristics. Here, we report a simple solution-processed method to progressively tune the work function of Ti₃C₂T_x MXene by exceeding 600 meV without sacrificing its other primary material properties, via a charge transfer doping mechanism. The underlying reason is attributed to the spontaneous electron withdrawing from MXene to the blended MoO₃ nanodots, which increase the hole concentration and consequently raises the work function of MXene, as also revealed by density functional theory calculations. The technique also holds other superiorities including suitability for MXene films of diverse thicknesses, sufficient adjustment latitude, excellent doping stability, and environmental friendliness. As a demonstration, the doping scheme significantly improves the performance of MXene/Si heterostructure-based photodetectors, rendering enhanced responsivity and specific detectivity from 110.2 mAW⁻¹ to 2.61 × 10¹¹ Jones to 494.9 mAW⁻¹ and 1.06 × 10¹³ Jones, respectively. The proposed technique not only offers a facile avenue for tuning the work function of MXenes towards electronic/optoelectronic applications, but also helps expand the application range of MXenes.