Black Phosphorus@MXene Heterojunction‐Engineered Carbon Nanotube Thermoelectric Films with Synergistic Energy Filtering and Phonon Scattering Effects

Abstract Organic thermoelectric (TE) materials incorporating carbon nanotubes (CNTs) attract substantial research interest due to their flexibility, cost‐effectiveness, and processability, showing significant promise for wearable TE devices. However, their practical applications are greatly limited by the low Seebeck coefficient ( S ) and high thermal conductivity ( κ ). To overcome these challenges, in this study, black phosphorus@MXene heterojunctions are rationally engineered into CNT matrix, creating TE composite film. This unique “2D heterojunction‐3D network” architecture leverages synergistic energy filtering and interfacial phonon scattering to achieve decoupled optimization of electrical conductivity ( σ ), S and κ . Consequently, the composite film attains a high power factor of 521.4 ± 7.7 µW m ⁻¹ K ⁻² at room temperature with a significantly suppressed κ , yielding a figure of merit of 0.0211. These metrics represent a substantial enhancement over pristine CNTs. Furthermore, the film exhibits excellent flexibility and structural stability, contributing to a flexible TE generator prototype with a high power density of 584 µW cm ⁻² under a temperature gradient of 60 K. This work provides a viable pathway for high‐performance, flexible TE materials in self‐powered wearable electronics for health monitoring and thermal management.