• Deionized water is identified as the optimal dispersing solvent for achieving tightly packed and highly oriented Ti3C2Tx nanosheets, enhancing film quality.
• Increasing centrifugal speed of MXene aqueous suspensions simultaneously boosts both Seebeck coefficient and electrical conductivity, yielding an ultrahigh power factor of ~156 μW m−1 K−2.
• Constructing MXene-based nanocomposites significantly enhances the Seebeck coefficient but disrupts nanosheet stacking, leading to reduced electrical conductivity.
• The study establishes a clear correlation between the thermoelectric performance of neat Ti3C2Tx films and the stacking density of nanosheets, guiding future MXene TE material design.